EVAL-AD73322LEB_技术文档

Low Cost, Low Power CMOS

General-Purpose Dual Analog Front End

a

AD73322L

FEATURES

Two 16-Bit A/D Converters

Two 16-Bit D/A Converters

FUNCTIONAL BLOCK DIAGRAM

AVDD1 AVDD2

DVDD

Programmable Input/Output Sample Rates

78 dB ADC SNR

78 dB DAC SNR

64 kS/s Maximum Sample Rate

–90 dB Crosstalk

Low Group Delay (25 ꢀs Typ per ADC Channel,

50 ꢀs Typ per DAC Channel)

AD73322L

VFBP1

VINP1

ADC CHANNEL 1

DAC CHANNEL 1

SDI

VINN1

VFBN1

SDIFS

VOUTP1

VOUTN1

SCLK

Programmable Input/Output Gain

Flexible Serial Port which Allows Up to Four Dual

Codecs to be Connected in Cascade Giving Eight

I/O Channels

Single (2.7 V to 3.3 V) Supply Operation

50 mW Typ Power Consumption at 3.0 V

Temperature Range: –40ꢁC to +105ꢁC

On-Chip Reference

SE

SPORT

REFOUT

REFCAP

REFERENCE

RESET

VFBP2

VINP2

MCLK

ADC CHANNEL 2

VINN2

VFBN2

SDOFS

SDO

VOUTP2

VOUTN2

DAC CHANNEL 2

AGND1 AGND2

28-Lead SOIC, TSSOP, and 44-Lead LQFP Packages

APPLICATIONS

General-Purpose Analog I/O

Speech Processing

DGND

Cordless and Personal Communications

Telephony

Active Control of Sound and Vibration

Data Communications

Wireless Local Loop

GENERAL DESCRIPTION

The A/D and D/A conversion channels feature programmable

input/output gains with ranges 38 dB and 21 dB respectively.

An on-chip reference voltage is included to allow single-

supply operation.

The AD73322L is a dual front-end processor for general pur-

pose applications including speech and telephony. It features

two 16-bit A/D conversion channels and two 16-bit D/A con-

version channels. Each channel provides 78 dB signal-to-noise

ratio over a voiceband signal bandwidth. It also features an

input-to-output gain network in both the analog and digital

domains. This is featured on both codecs and can be used for

impedance matching or scaling when interfacing to Subscriber

Line Interface Circuits (SLICs).

The sampling rate of the codecs is programmable with four

separate settings offering 64 kHz, 32 kHz, 16 kHz, and 8 kHz

sampling rates (from a master clock of 16.384 MHz).

A serial port (SPORT) allows easy interfacing of single or cas-

caded devices to industry standard DSP engines. The SPORT

transfer rate is programmable to allow interfacing to both fast

and slow DSP engines.

The AD73322L is particularly suitable for a variety of applica-

tions in the speech and telephony area, including low bit rate,

high quality compression, speech enhancement, recognition and

synthesis. The low group delay characteristic of the part makes

it suitable for single or multichannel active control applications.

The AD73322L is available in 28-lead SOIC, 28-lead TSSOP,

and 44-lead LQFP packages.

REV. 0

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, norforanyinfringementsofpatentsorotherrightsofthirdpartiesthat

may result from its use. No license is granted by implication or otherwise

under any patent or patent rights of Analog Devices.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781/329-4700

Fax: 781/326-8703

www.analog.com

(AVDD = 3 V ꢂ 10%; DVDD = 3 V ꢂ 10%; DGND = AGND = 0 V, f_DMCLK

=

AD73322L–SPECIFICATIONS¹^{16.384 MHz, f}_SAMP= 8 kHz; T_A= T_MINto T_MAX, unless otherwise noted.)

A, Y Versions

Parameter

Min

Typ

Max

Unit

Test Conditions/Comments

REFERENCE

REFCAP

Absolute Voltage, VREFCAP

REFCAP TC

REFOUT

1.08

1.2

50

1.32

V

ppm/°C 0.1 µF Capacitor Required from

REFCAP to AGND2

Typical Output Impedance

Absolute Voltage, V_REFOUT

Minimum Load Resistance

Maximum Load Capacitance

130

1.2

1

Ω

1.08

1.32

V

Unloaded

kΩ

pF

100

INPUT AMPLIFIER

Offset

Maximum Output Swing

Feedback Resistance

Feedback Capacitance

1.0

1.578

50

mV

V

kΩ

pF

Max Output Swing = (1.578/1.2) × VREFCAP

f_C= 32 kHz

100

ANALOG GAIN TAP

Gain at Maximum Setting

Gain at Minimum Setting

Gain Resolution

Gain Accuracy

Settling Time

+1

–1

5

1.0

0.5

Bits

%

µs

Gain Step Size = 0.0625

Output Unloaded

Tap Gain Change of –FS to +FS

Delay

ADC SPECIFICATIONS

DAC Unloaded

Maximum Input Range at VIN^{2, 3}

1.578

–2.85

1.0954

–6.02

V p-p

dBm

V p-p

dBm

Measured Differentially

Max Input = (1.578/1.2) × VREFCAP

Measured Differentially

Nominal Reference Level at VIN

(0 dBm0)

Absolute Gain

PGA = 0 dB

–2.0

–0.7

0.1

+0.5

dB

1.0 kHz, 0 dBm0

1.0 kHz, +3 dBm0 to –50 dBm0

Refer to TPC 1.

300 Hz to 3400 Hz; f_SAMP= 8 kHz, PUIA = 0

300 Hz to 3400 Hz; f_SAMP= 8 kHz, PUIA = 1

0 Hz to f_SAMP/2; f_SAMP= 8 kHz

Gain Tracking Error

Signal to (Noise + Distortion)

PGA = 0 dB

70

78

79

77.5

dB

Total Harmonic Distortion

PGA = 0 dB

Intermodulation Distortion

Idle Channel Noise Crosstalk

ADC-to-DAC

–86

–61

–72

–107

–75

dB

dBm0

dB

300 Hz to 3400 Hz; f_SAMP= 8 kHz

PGA = 0 dB

ADC Input Signal Level: 1.0 kHz, 0 dBm0

DAC Input at Idle

ADC-to-ADC

–92

dB

ADC1 Input Signal Level: 1.0 kHz, 0 dBm0

ADC2 Input at Idle. Input Amplifiers Bypassed

Input Amplifiers Included in Input Channel

PGA = 0 dB

–93

0

–65

dB

mV

dB

DC Offset

Power Supply Rejection

–20

+20

Input Signal Level at AVDD and DVDD

Pins: 1.0 kHz, 100 mV p-p Sine Wave

Group Delay^{4, 5}

25

20

µs

kΩ

Input Resistance at PGA^{2, 4, 6}

Input Amplifiers Bypassed

DIGITAL GAIN TAP

Gain at Maximum Setting

Gain at Minimum Setting

Gain Resolution

Delay

Settling Time

+1

–1

16

25

100

Bits

µs

Tested to 5 MSBs of Settings

Includes DAC Delay

Tap Gain Change from –FS to +FS; Includes

DAC Settling Time

–2–

REV. 0

AD73322L

A, Y Versions

Parameter

Min

Typ

Max

Unit

Test Conditions/Comments

DAC SPECIFICATIONS

Maximum Voltage Output Swing²

Single-Ended

DAC Unloaded

1.578

–2.85

3.156

3.17

V p-p

dBm

V p-p

dBm

PGA = 6 dB

Max Output = (1.578/1.2) × VREFCAP

PGA = 6 dB

Differential

Max Output = 2 × ([1.578/1.2] × VREFCAP)

Nominal Voltage Output Swing (0 dBm0)

Single-Ended

1.0954

–6.02

2.1909

0

V p-p

dBm

V p-p

dBm

V

PGA = 6 dB

Differential

Output Bias Voltage

1.2

REFOUT Unloaded

Absolute Gain

Gain Tracking Error

Signal to (Noise + Distortion) at 0 dBm0

PGA = 0 dB

–1.75

–0.6

0.1

+0.75 dB

1.0 kHz, 0 dBm0; Unloaded

1.0 kHz, +3 dBm0 to –50 dBm0

Refer to TPC 2.

dB

72

78.5

dB

300 Hz to 3400 Hz; f_SAMP= 8 kHz

Total Harmonic Distortion at 0 dBm0

PGA = 0 dB

Intermodulation Distortion

Idle Channel Noise Crosstalk

DAC-to-ADC

–89

–77

–81

–73

–75

dB

dBm0

dB

300 Hz to 3400 Hz; f_SAMP= 8 kHz

PGA = 0 dB

ADC Input Signal Level: AGND; DAC

Output Signal Level: 1.0 kHz, 0 dBm0

Input Amplifiers Bypassed

–74

–102

dB

Input Amplifiers Included in Input Channel

DAC1 Output Signal Level: AGND; DAC2

Output Signal Level: 1.0 kHz, 0 dBm0

Input Signal Level at AVDD and DVDD

Pins: 1.0 kHz, 100 mV p-p Sine Wave

Interpolator Bypassed

DAC-to-DAC

Power Supply Rejection

Group Delay^{4, 5}

–65

dB

25

50

+5

µs

Output DC Offset^{2, 7}

–50

+60

mV

2, 8

Minimum Load Resistance, R_L

Single-Ended⁴

Differential

150

Ω

2, 8

Maximum Load Capacitance, C_L

Single-Ended

Differential

500

100

pF

FREQUENCY RESPONSE

(ADC and DAC)⁹Typical Output

Frequency (Normalized to FS)

0

dB

0.03125

0.0625

0.125

0.1875

0.25

0.3125

0.375

0.4375

> 0.5

–0.1

–0.25

–0.6

–1.4

–2.8

–4.5

–7.0

–9.5

< –12.5

–3–

REV. 0

AD73322L

A, Y Versions

Typ

Parameter

Min

Max

Unit

Test Conditions/Comments

LOGIC INPUTS

V

_INH, Input High Voltage

DVDD – 0.8

0

–10

DVDD

0.8

+10

10

V

µA

pF

V_INL, Input Low Voltage

I_IH, Input Current

C_IN, Input Capacitance

LOGIC OUTPUT

V_OH, Output High Voltage

V_OL, Output Low Voltage

Three-State Leakage Current

DVDD – 0.4

0

–10

DVDD

0.4

+10

V

µA

|IOUT| ≤ 100 µA

POWER SUPPLIES

AVDD1, AVDD2

DVDD

2.7

3.3

V

10

I_DD

See Table I

NOTES

¹Operating temperature range as follows: A Grade, T_MIN= –40°C, T_MAX= +85°C; Y Grade, T_MIN= –40°C, T_MAX= +105°C.

²Test conditions: Input PGA set for 0 dB gain, Output PGA set for 6 dB gain, no load on analog outputs (unless otherwise noted).

³At input to sigma-delta modulator of ADC.

⁴Guaranteed by design.

⁵Overall group delay will be affected by the sample rate and the external digital filtering.

⁶The ADC’s input impedance is inversely proportional to DMCLK and is approximated by: (3.3 × 10¹¹)/DMCLK.

⁷Between VOUTP1 and VOUTN1 or between VOUTP2 and VOUTN2.

⁸At VOUT output.

⁹Frequency responses of ADC and DAC measured with input at audio reference level (the input level that produces an output level of –10 dBm0), with 38 dB pream-

plifier bypassed and input gain of 0 dB.

¹⁰Test Conditions: no load on digital inputs, analog inputs ac-coupled to ground, no load on analog outputs.

Specifications subject to change without notice.

Table I. Current Summary (AVDD = DVDD = 3.3 V)

Analog

Current

Digital

Current

Total Current

(Typ)

Total Current

(Max)

MCLK

SE ON

Conditions

Comments

ADCs On Only

DACs On Only

ADCs and DACs On

ADCs and DACs

and Input Amps On

ADCs and DACs

and AGT On

All Sections On

REFCAP On Only

REFCAP and

3.4

8.8

11.6

6.3

6.5

7.0

9.7

15.3

18.6

12

20

23

1

YES

REFOUT Disabled

13.8

7.0

20.8

26

1

YES

REFOUT Disabled

13.2

17.2

0.65

7.0

0

20.2

24.2

0.67

26

31

1.25

1

0

YES

NO

REFOUT On Only

All Sections Off

2.56

0

1.25

2.57

1.25

4.5

1.8

0

NO

YES

MCLK Active Levels Equal to

0 V and DVDD

All Sections Off

0 µA

12.5 µA

12.7 µA

40 µA

0

NO

Digital Inputs Static and Equal

to 0 V or DVDD

The above values are in mA and are typical values unless otherwise noted.

–4–

REV. 0

AD73322L

Table II. Signal Ranges

3 V Power Supply

5VEN = 0

VREFCAP

VREFOUT

ADC

1.2 V 10%

1.578 V p-p

1.0954 V p-p

Maximum Input Range at V_IN

Nominal Reference Level

Maximum Voltage Output Swing

Single-Ended

DAC

1.578 V p-p

3.156 V p-p

Differential

Nominal Voltage Output Swing

Single-Ended

Differential

1.0954 V p-p

2.1909 V p-p

VREFOUT

Output Bias Voltage

(AVDD = 3 V ꢂ 10%; DVDD = 3 V ꢂ 10%; AGND = DGND = 0 V; T_A= T_MlNto T_MAX, unless

otherwise noted.)

TIMING CHARACTERISTICS

Limit at

Parameter

T_A= –40ꢁC to +105ꢁC

Unit

Description

Clock Signals

See Figure 1

t₁

t₂

t₃

61

24.4

ns min

MCLK Period

MCLK Width High

MCLK Width Low

Serial Port

See Figures 3 and 4

t₄

t₅

t₆

t₇

t₈

t₉

t₁₀

t₁₁

t₁₂

t₁₃

t₁

ns min

ns max

ns min

ns max

SCLK Period

SCLK Width High

SCLK Width Low

SDI/SDIFS Setup Before SCLK Low

SDI/SDIFS Hold After SCLK Low

SDOFS Delay from SCLK High

SDOFS Hold After SCLK High

SDO Hold After SCLK High

SDO Delay from SCLK High

SCLK Delay from MCLK

0.4 × t₁

20

0

10

30

Specifications subject to change without notice.

REV. 0

–5–

AD73322L

t₁

100ꢀA

I

OL

t₂

TO OUTPUT

2.1V

C

15pF

L

I

OH

t₃

Figure 1. MCLK Timing

Figure 2. Load Circuit for Timing Specifications

t₂

t₁

t₃

MCLK

SCLK*

t₁₃

t₆

t₅

t₄

* SCLK IS INDIVIDUALLY PROGRAMMABLE

IN FREQUENCY (MCLK/4 SHOWN HERE).

Figure 3. SCLK Timing

SE (I)

THREE-

STATE

SCLK (O)

SDIFS (I)

t₇

t₈

t₇

SDI (I)

D15

D14

D1

D0

D15

t₉

t₁₀

THREE-

SDOFS (O) STATE

THREE-

STATE

t₁₁

t₁₂

SDO (O)

D15

D2

D1

D0

D15

D14

Figure 4. Serial Port (SPORT)

–6–

REV. 0

AD73322L

TSSOP, θ_JAThermal Impedance . . . . . . . . . . . . . . 97.9°C/W

Lead Temperature, Soldering

ABSOLUTE MAXIMUM RATINGS*

(T_A= 25°C unless otherwise noted)

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . . 215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C

*Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent damage to the device. This is a stress rating only; functional operation of the

device at these or any other conditions above those listed in the operational

sections of this specification is not implied. Exposure to absolute maximum rating

conditions for extended periods may affect device reliability.

AVDD, DVDD to GND . . . . . . . . . . . . . . . –0.3 V to +4.6 V

AGND to DGND . . . . . . . . . . . . . . . . . . . . –0.3 V to +0.3 V

Digital I/O Voltage to DGND . . . –0.3 V to (DVDD + 0.3 V)

Analog I/O Voltage to AGND . . . –0.3 V to (AVDD + 0.3 V)

Operating Temperature Range

Industrial (A Version) . . . . . . . . . . . . . . . –40°C to +85°C

Extended (Y Version) . . . . . . . . . . . . . . . . –40°C to +105°C

Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C

Maximum Junction Temperature . . . . . . . . . . . . . . . . 150°C

SOIC, θ_JAThermal Impedance . . . . . . . . . . . . . . . 71.4°C/W

Lead Temperature, Soldering

ORDERING GUIDE

Temperature

Range

Package

Descriptions

Package

Option

Model

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . . 215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C

LQFP, θ_JAThermal Impedance . . . . . . . . . . . . . . . 53.2°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . . 215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C

AD73322LAR

AD73322LARU

AD73322LAST

–40°C to +85°C

Wide Body SOIC

Thin Shrink TSSOP RU-28

Plastic Thin Quad

Flatpack (LQFP)

R-28

ST-44A

AD73322LYR

AD73322LYRU

AD73322LYST

–40°C to +105°C Wide Body SOIC

–40°C to +105°C Thin Shrink TSSOP RU-28

–40°C to +105°C Plastic Thin Quad

Flatpack (LQFP)

R-28

ST-44A

EVAL-AD73322LEB

Evaluation Board

CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily

accumulate on the human body and test equipment and can discharge without detection. Although

the AD73322L features proprietary ESD protection circuitry, permanent damage may occur on

devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are

recommended to avoid performance degradation or loss of functionality.

WARNING!

ESD SENSITIVE DEVICE

PIN CONFIGURATIONS

28-Lead Wide Body SOIC

(R-28)

28-Lead Thin Shrink TSSOP

(RU-28)

44-Lead Plastic Thin Quad Flatpack (LQFP)

(ST-44A)

VINP1

1

2

28

27

26

25

24

23

22

21

20

19

18

17

16

15

VFBN2

VINP1

1

2

28 VFBN2

27

26

25

24

23

22

21

VFBP1

VINN1

VINN2

VFBP2

VINP2

VFBP1

VINN1

VINN2

44 43 42 41 40 39 38 37 36 35 34

3

VFBP2

REFOUT

REFCAP

AVDD2

AGND2

DGND

NC

1

2

3

4

5

6

7

8

9

33

32

4

VFBN1

REFOUT

REFCAP

AVDD2

AGND2

DGND

VFBN1

REFOUT

REFCAP

AVDD2

AGND2

DGND

VINP2

PIN 1

IDENTIFIER

VOUTN1

5

VOUTN1

VOUTP1

VOUTN2

VOUTP2

AVDD1

AGND1

SE

VOUTN1

VOUTP1

VOUTN2

VOUTP2

31 VOUTP1

30 NC

6

AD73322L

TOP VIEW

(Not to Scale)

AD73322L

TOP VIEW

(Not to Scale)

7

8

29

VOUTN2

AD73322L

9

20 AVDD1

TOP VIEW

28

VOUTP2

(Not to Scale)

10

11

12

13

14

10

11

12

13

14

19

18

17

16

15

DVDD

AGND1

SE

27

NC

RESET

SCLK

RESET

SCLK

26 AVDD1

SDI

25

AVDD1

MCLK

SDIFS

SDOFS

MCLK

SDIFS

SDOFS

DGND 10

DVDD

24 AGND1

23 AGND1

SDO

11

13

20

21 22

12

14 15 16 17 18 19

NC = NO CONNECT

REV. 0

–7–

AD73322L

PIN FUNCTION DESCRIPTIONS

Mnemonic

Function

VINP1

VFBP1

Analog Input to the inverting input amplifier on Channel 1’s positive input.

Feedback Connection from the output of the inverting amplifier on Channel 1’s positive input. When the input

amplifiers are bypassed, this pin allows direct access to the positive input of Channel 1’s sigma-delta modulator.

VINN1

VFBN1

Analog Input to the inverting input amplifier on Channel 1’s negative input.

Feedback connection from the output of the inverting amplifier on Channel 1’s negative input. When the input

amplifiers are bypassed, this pin allows direct access to the negative input of Channel 1’s sigma-delta modulator.

REFOUT

REFCAP

Buffered Reference Output, which has a nominal value of 1.2 V or 2.4 V, the value being dependent on the status

of Bit 5VEN (CRC:7). As the reference is common to the two codec units, the reference value is set by the wired

OR of the CRC:7 bits in Control Register C of each channel.

A bypass capacitor to AGND2 of 0.1 µF is required for the on-chip reference. The capacitor should be fixed to

this pin.

AVDD2

AGND2

DGND

DVDD

RESET

Analog Power Supply Connection.

Analog Ground/Substrate Connection2.

Digital Ground/Substrate Connection.

Digital Power Supply Connection.

Active Low Reset Signal. This input resets the entire chip, resetting the control registers and clearing the digital

circuitry.

SCLK

Serial Clock Output whose rate determines the serial transfer rate to/from the codec. It is used to clock data or

control information to and from the serial port (SPORT). The frequency of SCLK is equal to the frequency of the

master clock (MCLK) divided by an integer number—this integer number being the product of the external mas-

ter clock rate divider and the serial clock rate divider.

MCLK

SDO

Master Clock Input. MCLK is driven from an external clock signal.

Serial Data Output. Both data and control information may be output on this pin and are clocked on the positive

edge of SCLK. SDO is in three-state when no information is being transmitted and when SE is low.

SDOFS

SDIFS

Framing Signal Output for SDO Serial Transfers. The frame sync is one bit wide and is active one SCLK period

before the first bit (MSB) of each output word. SDOFS is referenced to the positive edge of SCLK. SDOFS is in

three-state when SE is low.

Framing Signal Input for SDI Serial Transfers. The frame sync is one bit wide and is valid one SCLK period

before the first bit (MSB) of each input word. SDIFS is sampled on the negative edge of SCLK and is ignored

when SE is low.

SDI

SE

Serial Data Input. Both data and control information may be input on this pin and are clocked on the negative

edge of SCLK. SDI is ignored when SE is low.

SPORT Enable. Asynchronous input enable pin for the SPORT. When SE is set low by the DSP, the output

pins of the SPORT are three-stated and the input pins are ignored. SCLK is also disabled internally in order to

decrease power dissipation. When SE is brought high, the control and data registers of the SPORT are at their

original values (before SE was brought low); however, the timing counters and other internal registers are at

their reset values.

AGND1

AVDD1

VOUTP2

VOUTN2

VOUTP1

VOUTN1

VINP2

Analog Ground/Substrate Connection.

Analog Power Supply Connection.

Analog Output from the Positive Terminal of Output Channel 2.

Analog Output from the Negative Terminal of Output Channel 2.

Analog Output from the Positive Terminal of Output Channel 1.

Analog Output from the Negative Terminal of Output Channel 1.

Analog Input to the inverting input amplifier on Channel 2’s positive input.

VFBP2

Feedback connection from the output of the inverting amplifier on Channel 2’s positive input. When the input

amplifiers are bypassed, this pin allows direct access to the positive input of Channel 2’s sigma-delta modulator.

VINN2

VFBN2

Analog Input to the inverting input amplifier on Channel 2’s negative input.

Feedback connection from the output of the inverting amplifier on Channel 2’s negative input. When the input

amplifiers are bypassed, this pin allows direct access to the negative input of Channel 2’s sigma-delta modulator.

–8–

REV. 0

AD73322L

TERMINOLOGY

ABBREVIATIONS

Absolute Gain

ADC

AFE

AGT

ALB

BW

Analog-to-Digital Converter.

Absolute gain is a measure of converter gain for a known signal.

Absolute gain is measured (differentially) with a 1 kHz sine wave at

0 dBm0 for the DAC and with a 1 kHz sine wave at 0 dBm0 for

the ADC. The absolute gain specification is used for gain track-

ing error specification.

Analog Front End.

Analog Gain Tap.

Analog Loop-Back.

Bandwidth.

Crosstalk

CRx

A Control Register where x is a placeholder for an

alphabetic character (A–E). There are five read/

write control registers on the AD73322L—desig-

nated CRA through CRE.

Crosstalk is due to coupling of signals from a given channel to

an adjacent channel. It is defined as the ratio of the amplitude of

the coupled signal to the amplitude of the input signal. Crosstalk

is expressed in dB.

CRx:n

A bit position, where n is a placeholder for a nu-

meric character (0–7), within a control register,

where x is a placeholder for an alphabetic charac-

ter (A–E). Position 7 represents the MSB and

Position 0 represents the LSB.

Gain Tracking Error

Gain tracking error measures changes in converter output for

different signal levels relative to an absolute signal level. The

absolute signal level is 0 dBm0 (equal to absolute gain) at 1 kHz

for the DAC and 0 dBm0 (equal to absolute gain) at 1 kHz for

the ADC. Gain tracking error at 0 dBm0 (ADC) and 0 dBm0

(DAC) is 0 dB by definition.

DAC

Digital-to-Analog Converter.

Digital Gain Tap.

DGT

Group Delay

DLB

Digital Loop-Back.

Group Delay is defined as the derivative of radian phase with

respect to radian frequency, dø(f)/df. Group delay is a measure

of average delay of a system as a function of frequency. A linear

system with a constant group delay has a linear phase response.

The deviation of group delay from a constant indicates the

degree of nonlinear phase response of the system.

DMCLK

Device (Internal) Master Clock. This is the inter-

nal master clock resulting from the external master

clock (MCLK) being divided by the on-chip mas-

ter clock divider.

FS

Full Scale.

FSLB

Frame Sync Loop-Back—where the SDOFS of

the final device in a cascade is connected to the

RFS and TFS of the DSP and the SDIFS of

first device in the cascade. Data input and out-

put occur simultaneously. In the case of NonFSLB,

SDOFS and SDO are connected to the Rx Port

of the DSP while SDIFS and SDI are connected

to the Tx Port.

Idle Channel Noise

Idle channel noise is defined as the total signal energy measured

at the output of the device when the input is grounded (mea-

sured in the frequency range 300 Hz–3400 Hz).

Intermodulation Distortion

With inputs consisting of sine waves at two frequencies, fa and

fb, any active device with nonlinearities will create distortion

products at sum and difference frequencies of mfa nfb where

m, n = 0, 1, 2, 3, etc. Intermodulation terms are those for which

neither m nor n is equal to zero. For final testing, the second

order terms include (fa + fb) and (fa – fb), while the third order

terms include (2fa + fb), (2fa – fb), (fa + 2fb) and (fa – 2fb).

PGA

SC

Programmable Gain Amplifier.

Switched Capacitor.

Sport Loop-Back.

SLB

SNR

SPORT

THD

VBW

Signal-to-Noise Ratio.

Serial Port.

Power Supply Rejection

Power supply rejection measures the susceptibility of a device to

noise on the power supply. Power supply rejection is measured

by modulating the power supply with a sine wave and measuring

the noise at the output (relative to 0 dB).

Total Harmonic Distortion.

Voice Bandwidth.

Sample Rate

The sample rate is the rate at which the ADC updates its output

register and the DAC updates its output from its input register.

The sample rate can be chosen from a list of four that are fixed

relative to the DMCLK. Sample rate is set by programming bits

DIR0-1 in Control Register B of each channel.

SNR+THD

Signal-to-noise ratio plus harmonic distortion is defined to be

the ratio of the rms value of the measured input signal to the

rms sum of all other spectral components in the frequency range

300 Hz–3400 Hz, including harmonics but excluding dc.

REV. 0

–9–

–Typical Performance Characteristics

AD73322L

80

70

60

50

40

30

20

10

0

80

70

60

50

40

30

20

10

0

–10

–85 –75

–65

–55

–45

–35

– dBm0

–25

–15

–5

5

3.17

–85

–75

–65

–55

–45 –35

V – dBm0

IN

–25

–15

–5

5

3.17

V

IN

TPC 1. S/(N+D) vs. V_IN(ADC @ 3 V) over Voiceband

Bandwidth (300 Hz–3.4 kHz)

TPC 2. S/(N+D) vs. V_IN(DAC @ 3 V) over Voiceband

Bandwidth (300 Hz–3.4 kHz)

AVDD1

AVDD2

DVDD

VFBN1

VINN1

SDI

ANALOG

SIGMA-DELTA

MODULATOR

ANALOG

LOOP

BACK

INVERT

SINGLE-ENDED

ENABLE

0/38dB

PGA

V

REF

DECIMATOR

SDIFS

SCLK

VINP1

VFBP1

GAIN

ꢂ1

GAIN

ꢂ1

VOUTP1

VOUTN1

DIGITAL

SIGMA-

CONTINUOUS

TIME

LOW-PASS

FILTER

SWITCHED

CAPACITOR

LOW-PASS

FILTER

1-BIT

DAC

INTER-

POLATOR

+6/15dB

PGA

RESET

DELTA

MODULATOR

MCLK

SE

SERIAL

I/O

PORT

REFCAP

REFOUT

REFERENCE

AD73322L

VFBN2

VINN2

SDO

SDOFS

ANALOG

SIGMA-DELTA

MODULATOR

ANALOG

LOOP

BACK

INVERT

SINGLE-ENDED

ENABLE

0/38dB

PGA

V

REF

DECIMATOR

VINP2

VFBP2

GAIN

ꢂ1

GAIN

ꢂ1

DIGITAL

SIGMA-

VOUTP2

VOUTN2

CONTINUOUS

TIME

LOW-PASS

FILTER

SWITCHED

CAPACITOR

LOW-PASS

FILTER

1-BIT

DAC

INTER-

POLATOR

+6/–15dB

PGA

DELTA

MODULATOR

AGND1

AGND2

DGND

Figure 5. Functional Block Diagram

–10–

REV. 0

AD73322L

interest to an out-of-band position (Figure 7b). The combina-

tion of these techniques, followed by the application of a digital

filter, sufficiently reduces the noise in band to ensure good

dynamic performance from the part (Figure 7c).

FUNCTIONAL DESCRIPTION

Encoder Channels

Both encoder channels consist of a pair of inverting op amps

with feedback connections that can be bypassed if required, a

switched capacitor PGA and a sigma-delta analog-to-digital

converter (ADC). An on-board digital filter, which forms part of

the sigma-delta ADC, also performs critical system-level filtering.

Due to the high level of oversampling, the input antialias require-

ments are reduced such that a simple single pole RC stage is

sufficient to give adequate attenuation in the band of interest.

BAND

Programmable Gain Amplifier

F /2

S

OF

Each encoder section’s analog front end comprises a switched

capacitor PGA, which also forms part of the sigma-delta modula-

tor. The SC sampling frequency is DMCLK/8. The PGA, whose

programmable gain settings are shown in Table III, may be used

to increase the signal level applied to the ADC from low output

sources such as microphones, and can be used to avoid placing

external amplifiers in the circuit. The input signal level to the

sigma-delta modulator should not exceed the maximum input

voltage permitted.

INTEREST

DMCLK/16

a.

NOISE SHAPING

BAND

OF

INTEREST

F /2

S

DMCLK/16

The PGA gain is set by bits IGS0, IGS1 and IGS2 (CRD:0–2)

in control register D.

b.

Table III. PGA Settings for the Encoder Channel

IGS2

IGS1

IGS0

Gain (dB)

DIGITAL FILTER

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

6

BAND

OF

12

18

20

26

32

38

F /2

S

INTEREST

DMCLK/16

c.

Figure 6. Sigma-Delta Noise Reduction

Figure 7 shows the various stages of filtering that are employed

in a typical AD73322L application. In Figure 7a we see the trans-

fer function of the external analog antialias filter. Even though it

is a single RC pole, its cutoff frequency is sufficiently far away

from the initial sampling frequency (DMCLK/8) that it takes

care of any signals that could be aliased by the sampling fre-

quency. This also shows the major difference between the initial

oversampling rate and the bandwidth of interest. In Figure 7b,

the signal and noise-shaping responses of the sigma-delta modu-

lator are shown. The signal response provides further rejection

of any high frequency signals while the noise-shaping will push

the inherent quantization noise to an out-of-band position. The

detail of Figure 7c shows the response of the digital decimation

filter (Sinc-cubed response) with nulls every multiple of DMCLK/

256, which corresponds to the decimation filter update rate

for a 64 kHz sampling. The nulls of the Sinc3 response corre-

spond with multiples of the chosen sampling frequency. The

final detail in Figure 7d shows the application of a final anti-

alias filter in the DSP engine. This has the advantage of being

implemented according to the user’s requirements and available

MIPS. The filtering in Figures 7a through 7c is implemented in

the AD73322L.

ADC

Both ADCs consist of an analog sigma-delta modulator and a

digital antialiasing decimation filter. The sigma-delta modu-

lator noise-shapes the signal and produces 1-bit samples at a

DMCLK/8 rate. This bitstream, representing the analog input

signal, is input to the antialiasing decimation filter. The decimation

filter reduces the sample rate and increases the resolution.

Analog Sigma-Delta Modulator

The AD73322L’s input channels employ a sigma-delta conversion

technique, which provides a high resolution 16-bit output with

system filtering being implemented on-chip.

Sigma-delta converters employ a technique known as over-

sampling, where the sampling rate is many times the highest

frequency of interest. In the case of the AD73322L, the initial

sampling rate of the sigma-delta modulator is DMCLK/8. The

main effect of oversampling is that the quantization noise is

spread over a very wide bandwidth, up to F_S/2 = DMCLK/16

(Figure 7a). This means that the noise in the band of interest is

much reduced. Another complementary feature of sigma-delta

converters is the use of a technique called noise-shaping. This

technique has the effect of pushing the noise from the band of

REV. 0

–11–

AD73322L

Word growth in the decimator is determined by the sampling

rate. At 64 kHz sampling, where the oversampling ratio between

sigma-delta modulator and decimator output equals 32, there

are five bits per stage of the three-stage Sinc3 filter. Due to symme-

try within the sigma-delta modulator, the LSB will always be a

zero; therefore, the 16-bit ADC output word will have 2 LSBs

equal to zero, one due to the sigma-delta symmetry and the

other being a padding zero to make up the 16-bit word. At

lower sampling rates, decimator word growth will be greater

than the 16-bit sample word, therefore truncation occurs in

transferring the decimator output as the ADC word. For example,

at 8 kHz sampling, word growth reaches 24 bits due to the OSR

of 256 between sigma-delta modulator and decimator output.

This yields eight bits per stage of the three-stage Sinc3 filter.

F

= 4kHz

F

= DMCLK/8

B

SINIT

a. Analog Antialias Filter Transfer Function

SIGNAL TRANSFER FUNCTION

ADC Coding

NOISE TRANSFER FUNCTION

The ADC coding scheme is in twos complement format (see

Figure 8). The output words are formed by the decimation

filter, which grows the word length from the single-bit output

of the sigma-delta modulator to a word length of up to 24 bits

(depending on decimation rate chosen), which is the final out-

put of the ADC block. In Data Mode this value is truncated to

16 bits for output on the Serial Data Output (SDO) pin.

F

= 4kHz

F

= DMCLK/8

B

SINIT

b. Analog Sigma-Delta Modulator Transfer Function

V

+ (V

ꢃ 0.32875)

REF

INN

REF

ANALOG

INPUT

V

REF

F

= 4kHz

F

= DMCLK/256

B

SINTER

V

INP

V

– (V

ꢃ 0.32875)

REF

c. Digital Decimator Transfer Function

10...00

00...00

01...11

ADC CODE DIFFERENTIAL

V

+ (V

ꢃ 0.6575)

REF

V

INN

ANALOG

INPUT

V

INP

F

= 4kHz

V

– (V ꢃ 0.6575)

REF

F

= 8kHz

F

= DMCLK/256

B

REF

SFINAL

SINTER

d. Final Filter LPF (HPF) Transfer Function

Figure 7. ADC Frequency Responses

10...00

00...00

ADC CODE SINGLE-ENDED

01...11

Figure 8. ADC Transfer Function

Decimation Filter

In mixed Control/Data Mode, the resolution is fixed at 15 bits,

with the MSB of the 16-bit transfer being used as a flag bit to

indicate either control or data in the frame.

The digital filter used in the AD73322L carries out two important

functions. Firstly, it removes the out-of-band quantization

noise, which is shaped by the analog modulator and secondly,

it decimates the high frequency bit stream to a lower rate 16-

bit word.

Decoder Channel

The decoder channels consist of digital interpolators, digital

sigma-delta modulators, single-bit digital-to-analog converters

(DAC), analog smoothing filters and programmable gain ampli-

fiers with differential outputs.

The antialiasing decimation filter is a sinc-cubed digital filter

that reduces the sampling rate from DMCLK/8 to DMCLK/256,

and increases the resolution from a single bit to 15 bits or greater

(depending on chosen sampling rate). Its Z transform is given as:

DAC Coding

[(1 – Z ^–N)/(1 – Z ^–1)]³

The DAC coding scheme is in twos complement format with

0x7FFF being full-scale positive and 0x8000 being full-

scale negative.

where N is set by the sampling rate (N = 32 @ 64 kHz sam-

pling. . . N = 256 @ 8 kHz sampling). Thus when the sampling

rate is 64 kHz, a minimal group delay of 25 µs can be achieved.

–12–

REV. 0

AD73322L

Interpolation Filter

Differential Output Amplifiers

The anti-imaging interpolation filter is a sinc-cubed digital filter

that up-samples the 16-bit input words from the input sample

rate to a rate of DMCLK/8, while filtering to attenuate images

produced by the interpolation process. Its Z transform is given as:

The decoder has a differential analog output pair (VOUTP and

VOUTN). The output channel can be muted by setting the

MUTE bit (CRD:7) in Control Register D. The output signal is

dc-biased to the codec’s on-chip voltage reference.

[(1 – Z^–N)/(1 – Z ^–1)]³

Voltage Reference

The AD73322L reference, REFCAP, is a bandgap reference

that provides a low noise, temperature-compensated reference

to the DAC and ADC. A buffered version of the reference is

also made available on the REFOUT pin and can be used to

bias other external analog circuitry. The reference has a default

nominal value of 1.2 V.

where N is determined by the sampling rate (N = 32 @ 64 kHz .

. . N = 256 @ 8 kHz). The DAC receives 16-bit samples from

the host DSP processor at the programmed sample rate of

DMCLK/N. If the host processor fails to write a new value to

the serial port, the existing (previous) data is read again. The

data stream is filtered by the anti-imaging interpolation filter,

but there is an option to bypass the interpolator for the mini-

mum group delay configuration by setting the IBYP bit (CRE:5)

of Control register E. The interpolation filter has the same char-

acteristics as the ADC’s antialiasing decimation filter.

The reference output (REFOUT) can be enabled for biasing

external circuitry by setting the RU bit (CRC:6) of CRC.

ANALOG

LOOP-BACK

SELECT

SINGLE-

ENDED

ENABLE

INVERTING

OP AMPS

The output of the interpolation filter is fed to the DAC’s digital

sigma-delta modulator, which converts the 16-bit data to 1-bit

samples at a rate of DMCLK/8. The modulator noise-shapes

the signal so that errors inherent to the process are minimized in

the passband of the converter. The bit-stream output of the

sigma-delta modulator is fed to the single-bit DAC where it is

converted to an analog voltage.

INVERT

VFBN1

VINN1

0/38dB

PGA

V

REF

VINP1

Analog Smoothing Filter and PGA

V

REF

VFBP1

GAIN

The output of the single-bit DAC is sampled at DMCLK/8,

therefore it is necessary to filter the output to reconstruct the

low frequency signal. The decoder’s analog smoothing filter

consists of a continuous-time filter preceded by a third-order

switched-capacitor filter. The continuous-time filter forms part

of the output programmable gain amplifier (PGA). The PGA

can be used to adjust the output signal level from –15 dB to

+6 dB in 3 dB steps, as shown in Table IV. The PGA gain is

set by bits OGS0, OGS1 and OGS2 (CRD:4-6) in Control

Register D.

ꢂ1

ANALOG GAIN

TAP

VOUTP1

VOUTN1

CONTINUOUS

TIME

LOW-PASS

FILTER

+6/–15dB

PGA

AD73322L

REFCAP

REFOUT

REFERENCE

Table IV. PGA Settings for the Decoder Channel

Figure 9. Analog Input/Output Section

OGS2

OGS1

OGS0

Gain (dB)

Analog and Digital Gain Taps

0

1

0

1

0

1

0

1

0

1

0

1

0

1

+6

+3

0

–3

–6

–9

–12

–15

The AD73322L features analog and digital feedback paths

between input and output. The amount of feedback is deter-

mined by the gain setting which is programmed in the control

registers. This feature can typically be used for balancing the

effective impedance between input and output when used in

Subscriber Line Interface Circuit (SLIC) interfacing.

REV. 0

–13–

AD73322L

MCLK

EXTERNAL

DMCLK INTERNAL

MCLK

DIVIDER

MCLK

DIVIDER

SCLK

3

DIVIDER

SE

SERIAL PORT 1

(SPORT 1)

SERIAL PORT 2

(SPORT 2)

RESET

SDIFS

SDI

RESET

SDOFS1

SDO1

SDOFS

SDO

SDIFS2

SDI2

SERIAL REGISTER 1

SERIAL REGISTER 2

2

8

CONTROL

REGISTER

1A

CONTROL

REGISTER

1B

CONTROL

REGISTER

1C

CONTROL

REGISTER

1D

CONTROL

REGISTER

1E

CONTROL

REGISTER

2A

CONTROL

REGISTER

2B

CONTROL

REGISTER

2C

CONTROL

REGISTER

2D

CONTROL

REGISTER

2E

8

16

CONTROL

REGISTER

1G

CONTROL

REGISTER

1F

CONTROL

REGISTER

2G

CONTROL

REGISTER

2F

CONTROL

REGISTER

1H

CONTROL

REGISTER

2H

Figure 10. SPORT Block Diagram

Analog Gain Tap

Digital Gain Tap

The analog gain tap is configured as a programmable differential

amplifier whose input is taken from the ADC’s input signal

path. The output of the analog gain tap is summed with the

output of the DAC. The gain is programmable using Control

Register F (CRF:0-4) to achieve a gain of –1 to +1 in 32 steps

with muting being achieved through a separate control setting

(Control Register F Bit 7). The gain increment per step is 0.0625.

The AGT is enabled by powering-up the AGT control bit in the

power control register (CRC:1). When this bit is set (=1) CRF

becomes an AGT control register with CRF:0-4 holding the

AGT coefficient, CRF:5 becomes an AGT enable and CRF:7

becomes an AGT mute control bit. Control bit CRF:5 connects/

disconnects the AGT output to the summer block at the output

of the DAC section while control bit CRF:7 overrides the gain

tap setting with a mute, (zero gain) setting. Table V shows the

gain versus digital setting for the AGT.

The digital gain tap features a programmable gain block whose

input is taken from the bitstream output of the ADC’s sigma-

delta modulator. This single bit input (1 or 0) is used to add or

subtract a programmable value, which is the digital gain tap setting,

to the output of the DAC section’s interpolator. The program-

mable setting has 16-bit resolution and is programmed using the

settings in Control Registers G and H. (See Table VI).

Table VI. Digital Gain Tap Settings*

DGT15–0 (Hex)

Gain

0x8000

0x9000

0xA000

0xC000

0xE000

0x0000

0x2000

0x4000

0x6000

0x7FFF

–1.00

–0.875

–0.75

–0.5

–0.25

0.00

+0.25

+0.05

+0.75

+0.99999

Table V. Analog Gain Tap Settings*

AGTC4 AGTC3 AGTC2 AGTC1 AGTC0 Gain (dB)

0

1

0

1

0

1

0

1

0

+1.00

+0.9375

+0.875

+0.8125

+0.75

*AGT and DGT weights are given for the case of VFBNx (connected to the

sigma-delta modulator’s positive input) being at a higher potential than VFBPx

(connected to the sigma-delta modulator’s negative input).

Serial Port (SPORT)

The codecs communicate with a host processor via the bidirec-

tional synchronous serial port (SPORT), which is compatible

with most modern DSPs. The SPORT is used to transmit and

receive digital data and control information. The dual codec is

implemented using two separate codec blocks that are internally

cascaded with serial port access to the input of Codec1 and the

output of Codec2. This allows other single or dual codec devices to

be cascaded together (up to a limit of eight codec units).

0

1

0

1

0

1

0

1

0

+0.0625

–0.0625

1

0

1

0

1

–0.875

–0.9375

–1.00

*AGT and DGT weights are given for the case of VFBNx (connected to the

sigma-delta modulator’s positive input) being at a higher potential than VFBPx

(connected to the sigma-delta modulator’s negative input).

–14–

REV. 0

AD73322L

In both transmit and receive modes, data is transferred at the

serial clock (SCLK) rate with the MSB being transferred first.

Due to the fact that the SPORT of each codec block uses a com-

mon serial register for serial input and output, communications

between an AD73322L codec and a host processor (DSP engine)

must always be initiated by the codecs themselves. In this con-

figuration the codecs are described as being in Master mode.

This ensures that there is no collision between input data and

output samples.

by the setting of Control Register B. The AD73322L features a

master clock divider that allows users the flexibility of dividing

externally available high frequency DSP or CPU clocks to gen-

erate a lower frequency master clock internally in the codec,

which may be more suitable for either serial transfer or sampling

rate requirements. The master clock divider has five divider

options (÷1 default condition, ÷2, ÷3, ÷4, ÷5) that are set by

loading the master clock divider field in Register B with the

appropriate code (see Table VII). Once the internal device master

clock (DMCLK) has been set using the master clock divider, the

sample rate and serial clock settings are derived from DMCLK.

SPORT Overview

The AD73322L SPORT is a flexible, full-duplex, synchronous

serial port whose protocol has been designed to allow up to four

AD73322L devices (or combinations of AD73322L dual codecs

and AD73311 single codecs up to eight codec blocks) to be con-

nected, in cascade, to a single DSP via a six-wire interface. It has a

very flexible architecture that can be configured by programming

two of the internal control registers in each codec block. The

AD73322L SPORT has three distinct modes of operation: Control

Mode, Data Mode and Mixed Control/Data Mode.

The SPORT can work at four different serial clock (SCLK)

rates: chosen from DMCLK, DMCLK/2, DMCLK/4 or

DMCLK/8, where DMCLK is the internal or device master

clock resulting from the external or pin master clock being

divided by the master clock divider.

SPORT Register Maps

There are two register banks for each codec in the AD73322L:

the control register bank and the data register bank. The con-

trol register bank consists of eight read/write registers, each

eight bits wide. Table XI shows the control register map for

the AD73322L. The first two control registers, CRA and CRB,

are reserved for controlling the SPORT. They hold settings for

parameters such as serial clock rate, internal master clock rate,

sample rate and device count. As both codecs are internally

cascaded, registers CRA and CRB on each codec must be pro-

grammed with the same setting to ensure correct operation (this

is shown in the programming examples). The other five registers;

CRC through CRH are used to hold control settings for the

ADC, DAC, Reference, Power Control and Gain Tap sections

of the device. It is not necessary that the contents of CRC

through CRH on each codec be similar. Control registers are

written to on the negative edge of SCLK. The data register

bank consists of two 16-bit registers that are the DAC and

ADC registers.

NOTE: As each codec has its own SPORT section, the register

settings in both SPORTs must be programmed. The registers

that control SPORT and sample rate operation (CRA and CRB)

must be programmed with the same values, otherwise incorrect

operation may occur.

In Control Mode (CRA:0 = 0), the device’s internal configura-

tion can be programmed by writing to the eight internal control

registers. In this mode, control information can be written to or

read from the codec. In Data Mode (CRA:0 = 1), (CRA:1 = 0),

information sent to the device is used to update the decoder

section (DAC), while the encoder section (ADC) data is read

from the device. In this mode, only DAC and ADC data is

written to or read from the device. Mixed mode (CRA:0 = 1

and CRA:1 = 1) allows the user to choose whether the informa-

tion being sent to the device contains either control information

or DAC data. This is achieved by using the MSB of the 16-bit

frame as a flag bit. Mixed mode reduces the resolution to 15 bits

with the MSB being used to indicate whether the information in

the 16-bit frame is control information or DAC/ADC data.

Master Clock Divider

The AD73322L features a programmable master clock divider

that allows the user to reduce an externally available master

clock, at pin MCLK, by one of the ratios 1, 2, 3, 4 or 5 to pro-

duce an internal master clock signal (DMCLK) that is used to

calculate the sampling and serial clock rates. The master clock

divider is programmable by setting CRB:4-6. Table VII shows

the division ratio corresponding to the various bit settings. The

default divider ratio is divide-by-one.

The SPORT features a single 16-bit serial register that is used

for both input and output data transfers. As the input and out-

put data must share the same register, some precautions must be

observed. The primary precaution is that no information must

be written to the SPORT without reference to an output sample

event, which is when the serial register will be overwritten with

the latest ADC sample word. Once the SPORT starts to output

the latest ADC word, it is safe for the DSP to write new control

or data words to the codec. In certain configurations, data can

be written to the device to coincide with the output sample being

shifted out of the serial register—see section on interfacing devices.

The serial clock rate (CRB:2–3) defines how many 16-bit words

can be written to a device before the next output sample event

will happen.

Table VII. DMCLK (Internal) Rate Divider Settings

MCD2

MCD1

MCD0

DMCLK Rate

0

1

0

1

0

1

0

1

0

1

0

1

0

1

MCLK

MCLK/2

MCLK/3

MCLK/4

MCLK/5

MCLK

The SPORT block diagram shown in Figure 10 details the

blocks associated with Codecs 1 and 2, including the eight

control registers (A–H), external MCLK to internal DMCLK

divider and serial clock divider. The divider rates are controlled

REV. 0

–15–

AD73322L

Serial Clock Rate Divider

Table IX. Sample Rate Divider Settings

The AD73322L features a programmable serial clock divider

that allows users to match the serial clock (SCLK) rate of the

data to that of the DSP engine or host processor. The maximum

SCLK rate available is DMCLK and the other available rates

are: DMCLK/2, DMCLK/4 and DMCLK/8. The slowest rate

(DMCLK/8) is the default SCLK rate. The serial clock divider

is programmable by setting bits CRB:2–3. Table VIII shows the

serial clock rate corresponding to the various bit settings.

DIR1

DIR0

SCLK Rate

0

1

0

1

0

1

DMCLK/2048

DMCLK/1024

DMCLK/512

DMCLK/256

DAC Advance Register

The loading of the DAC is internally synchronized with the

unloading of the ADC data in each sampling interval. The

default DAC load event happens one SCLK cycle before the

SDOFS flag is raised by the ADC data being ready. However,

this DAC load position can be advanced before this time by

modifying the contents of the DAC advance field in Control

Register E (CRE:0–4). The field is five bits wide, allowing 31

increments of weight 1/(F_S× 32); see Table X. The sample rate

F_Sis dependent on the setting of both the MCLK divider and

the Sample Rate divider; see Tables VII and IX. In certain cir-

cumstances this DAC update adjustment can reduce the group

delay when the ADC and DAC are used to process data in series.

Appendix C details how the DAC advance feature can be used.

Table VIII. SCLK Rate Divider Settings

SCD1

SCD0

SCLK Rate

0

1

0

1

0

1

DMCLK/8

DMCLK/4

DMCLK/2

DMCLK

Sample Rate Divider

The AD73322L features a programmable sample rate divider

that allows users flexibility in matching the codec’s ADC and

DAC sample rates (decimation/interpolation rates) to the needs

of the DSP software. The maximum sample rate available is

DMCLK/256, which offers the lowest conversion group delay,

while the other available rates are: DMCLK/512, DMCLK/

1024 and DMCLK/2048. The slowest rate (DMCLK/2048) is

the default sample rate. The sample rate divider is program-

mable by setting bits CRB:0-1. Table IX shows the sample

rate corresponding to the various bit settings.

NOTE: The DAC advance register should not be changed while

the DAC section is powered up.

Table X. DAC Timing Control

DA4

DA3

DA2

DA1

DA0

Time Advance

0

1

0

1

0

0 s

1/(F_S× 32) s

2/(F_S× 32) s

1

0

1

30/(F_S× 32) s

31/(F_S× 32) s

–16–

REV. 0

AD73322L

Table XI. Control Register Map

Address (Binary)

Name

Description

Type

Width

Reset Setting (Hex)

000

001

010

011

100

101

110

111

CRA

CRB

CRC

CRD

CRE

CRF

CRG

CRH

Control Register A

Control Register B

Control Register C

Control Register D

Control Register E

Control Register F

Control Register G

Control Register H

R/W

8

0x00

Table XII. Control Word Description

15

14

13

Device Address

Frame

12

11

10

Register Address

Description

9

8

7

6

5

4

3

2

1

0

C/D

R/W

Register Data

Control

Bit 15

Control/Data

When set high, it signifies a control word in Program or Mixed Program/Data Modes. When

set low, it signifies a data word in Mixed Program/Data Mode or an invalid control word in

Program Mode.

Bit 14

Read/Write

When set low, it tells the device that the data field is to be written to the register selected by

the register field setting provided the address field is zero. When set high, it tells the device

that the selected register is to be written to the data field in the input serial register and that

the new control word is to be output from the device via the serial output.

Bits 13–11

Device Address

This 3-bit field holds the address information. Only when this field is zero is a device

selected. If the address is not zero, it is decremented and the control word is passed out of

the device via the serial output.

Bits 10–8

Bits 7–0

Register Address

Register Data

This 3-bit field is used to select one of the eight control registers on the AD73322L.

This 8-bit field holds the data that is to be written to or read from the selected register

provided the address field is zero.

REV. 0

–17–

AD73322L

Table XIII. Control Register A Description

CONTROL REGISTER A

7

6

5

4

3

2

1

0

DATA/

RESET

DC2

DC1

DC0

SLB

DLB

MM

PGM

Bit

Name

Description

0

1

2

3

4

5

6

7

DATA/PGM Operating Mode (0 = Program; 1 = Data Mode)

MM

DLB

SLB

DC0

DC1

DC2

RESET

Mixed Mode (0 = Off; 1 = Enabled)

Digital Loop-Back Mode (0 = Off; 1 = Enabled)

SPORT Loop-Back Mode (0 = Off; 1 = Enabled)

Device Count (Bit 0)

Device Count (Bit 1)

Device Count (Bit 2)

Software Reset (0 = Off; 1 = Initiates Reset)

Table XIV. Control Register B Description

CONTROL REGISTER B

7

6

5

4

3

2

1

0

—

RU

PUREF PUDAC PUADC

PUIA

PUAGT

PU

Bit

Name

Description

0

1

2

3

4

5

6

7

DIR0

DIR1

Decimation/Interpolation Rate (Bit 0)

Decimation/Interpolation Rate (Bit 1)

Serial Clock Divider (Bit 0)

Serial Clock Divider (Bit 1)

Master Clock Divider (Bit 0)

Master Clock Divider (Bit 1)

Master Clock Divider (Bit 2)

Control Echo Enable (0 = Off; 1 = Enabled)

SCD0

SCD1

MCD0

MCD1

MCD2

CEE

Table XV. Control Register C Description

CONTROL REGISTER C

7

6

5

4

3

2

1

0

MUTE

OGS2

OGS1

OGS0

RMOD

IGS2

IGS1

IGS0

Bit

Name

Description

0

1

2

3

4

5

6

7

PU

PUAGT

PUIA

PUADC

PUDAC

PUREF

RU

Power-Up Device (0 = Power-Down; 1 = Power On)

Analog Gain Tap Power (0 = Power-Down; 1 = Power On)

Input Amplifier Power (0 = Power-Down; 1 = Power On)

ADC Power (0 = Power-Down; 1 = Power On)

DAC Power (0 = Power-Down; 1 = Power On)

REF Power (0 = Power-Down; 1 = Power On)

REFOUT Use (0 = Disable REFOUT; 1 = Enable REFOUT)

Reserved, must be programmed to 0.

—

–18–

REV. 0

AD73322L

Table XVI. Control Register D Description

CONTROL REGISTER D

CONTROL REGISTER E

CONTROL REGISTER F

7

6

5

4

3

2

1

0

MUTE

OGS2

OGS1

OGS0

RMOD

IGS2

IGS1

IGS0

Bit

Name

Description

0

1

2

3

4

5

6

7

IGS0

IGS1

IGS2

RMOD

OGS0

OGS1

OGS2

MUTE

Input Gain Select (Bit 0)

Input Gain Select (Bit 1)

Input Gain Select (Bit 2)

Reset ADC Modulator (0 = Off; 1 = Reset Enabled)

Output Gain Select (Bit 0)

Output Gain Select (Bit 1)

Output Gain Select (Bit 2)

Output Mute (0 = Mute Off; 1 = Mute Enabled)

Table XVII. Control Register E Description

7

6

5

4

3

2

1

0

—

DGTE

IBYP

DA4

DA3

DA2

DA1

DA0

Bit

Name

Description

0

1

2

3

4

5

6

7

DA0

DA1

DA2

DA3

DA4

IBYP

DAC Advance Setting (Bit 0)

DAC Advance Setting (Bit 1)

DAC Advance Setting (Bit 2)

DAC Advance Setting (Bit 3)

DAC Advance Setting (Bit 4)

Interpolator Bypass (0 = Bypass Disabled; 1 = Bypass Enabled)

Digital Gain Tap Enable (0 = Disabled; 1 = Enabled)

Reserved (Program to 0)

DGTE

—

Table XVIII. Control Register F Description

7

6

5

4

3

2

1

0

ALB/

AGTM

SEEN/

AGTE

INV

AGTC4 AGTC3 AGTC2 AGTC1 AGTC0

Bit

Name

Description

0

1

2

3

4

5

AGTC0

AGTC1

AGTC2

AGTC3

AGTC4

SEEN/

AGTE

INV

Analog Gain Tap Coefficient (Bit 0)

Analog Gain Tap Coefficient (Bit 1)

Analog Gain Tap Coefficient (Bit 2)

Analog Gain Tap Coefficient (Bit 3)

Analog Gain Tap Coefficient (Bit 4)

Single-Ended Enable (0 = Disabled; 1 = Enabled)

Analog Gain Tap Enable (0 = Disabled; 1 = Enabled)

Input Invert (0 = Disabled; 1 = Enabled)

Analog Loopback of Output to Input (0 = Disabled; 1 = Enabled)

Analog Gain Tap Mute (0 = Off; 1 = Muted)

6

7

ALB/

AGTM

REV. 0

–19–

AD73322L

Table XIX. Control Register G Description

CONTROL REGISTER G

7

6

5

4

3

2

1

0

DGTC7 DGTC6 DGTC5 DGTC4 DGTC3 DGTC2 DGTC1 DGTC0

Bit

Name

Description

0

1

2

3

4

5

6

7

DGTC0

DGTC1

DGTC2

DGTC3

DGTC4

DGTC5

DGTC6

DGTC7

Digital Gain Tap Coefficient (Bit 0)

Digital Gain Tap Coefficient (Bit 1)

Digital Gain Tap Coefficient (Bit 2)

Digital Gain Tap Coefficient (Bit 3)

Digital Gain Tap Coefficient (Bit 4)

Digital Gain Tap Coefficient (Bit 5)

Digital Gain Tap Coefficient (Bit 6)

Digital Gain Tap Coefficient (Bit 7)

Table XX. Control Register H Description

CONTROL REGISTER H

7

6

5

4

3

2

1

0

DGTC15 DGTC14 DGTC13 DGTC12 DGTC11 DGTC10 DGTC9 DGTC8

Bit

Name

Description

0

1

2

3

4

5

6

7

DGTC8

DGTC9

Digital Gain Tap Coefficient (Bit 8)

Digital Gain Tap Coefficient (Bit 9)

Digital Gain Tap Coefficient (Bit 10)

Digital Gain Tap Coefficient (Bit 11)

Digital Gain Tap Coefficient (Bit 12)

Digital Gain Tap Coefficient (Bit 13)

Digital Gain Tap Coefficient (Bit 14)

Digital Gain Tap Coefficient (Bit 15)

DGTC10

DGTC11

DGTC12

DGTC13

DGTC14

DGTC15

–20–

REV. 0

AD73322L

OPERATION

Resetting the AD73322L

passed out of the device—either to the next device in a cascade or

back to the DSP engine. This 3-bit address format allows the

user to uniquely address any one of up to eight devices in a

cascade; please note that this addressing scheme is valid only

in sending control information to the device —a different format

is used to send DAC data to the device(s). As the AD73322L is

a dual codec, it features two separate device addresses for pro-

gramming purposes. If the AD73322L is used in a standalone

configuration connected to a DSP, the two device addresses

correspond to 0 and 1. If, on the other hand, the AD73322L

is configured in a cascade of multiple, dual or single codecs

(AD73322L or AD73311), its device addresses correspond with

its hardwired position in the cascade.

The RESET pin resets all the control registers. All registers are

reset to zero, indicating that the default SCLK rate (DMCLK/

8) and sample rate (DMCLK/2048) are at a minimum to ensure

that slow speed DSP engines can communicate effectively. As

well as resetting the control registers using the RESET pin, the

device can be reset using the RESET bit (CRA:7) in Control

Register A. Both hardware and software resets require four

DMCLK cycles. On reset, DATA/PGM (CRA:0) is set to 0

(default condition) thus enabling Program Mode. The reset

conditions ensure that the device must be programmed to the

correct settings after power-up or reset. Following a reset, the

SDOFS will be asserted 2048 DMCLK cycles after RESET

going high. The data that is output following reset and during

Program Mode is random and contains no valid information

until either data or mixed mode is set.

Following reset, when the SE pin is enabled, the codec responds

by raising the SDOFS pin to indicate that an output sample event

has occurred. Control words can be written to the device to

coincide with the data being sent out of the SPORT, as shown in

Figure 11, or they can lag the output words by a time interval

that should not exceed the sample interval. After reset, output

frame sync pulses will occur at a slower default sample rate,

which is DMCLK/2048, until Control Register B is programmed,

after which the SDOFS pulses will be set according to the contents

of DIR0-1. This is to allow slow controller devices to establish

communication with the AD73322L. During Program Mode,

the data output by the device is random and should not be

interpreted as ADC data.

Power Management

The individual functional blocks of the AD73322L can be

enabled separately by programming the power control register

CRC. It allows certain sections to be powered down if not

required, which adds to the device’s flexibility in that the user

need not incur the penalty of having to provide power for a

certain section if it is not necessary to their design. The power

control registers provide individual control settings for the major

functional blocks on each codec unit and also a global override

that allows all sections to be powered up by setting the bit.

Using this method the user could, for example, individually

enable a certain section, such as the reference (CRC:5), and

disable all others. The global power-up (CRC:0) can be used to

enable all sections, but if power-down is required using the

global control, the reference will still be enabled, in this case,

because its individual bit is set. Refer to Table XVI for details

of the settings of CRC.

SE

SCLK

SDOFS

SDO

SAMPLE WORD (DEVICE 2)

SAMPLE WORD (DEVICE 1)

NOTE: As both codec units share a common reference, the

reference control bits (CRC:5-7) in each SPORT are wire ORed

to allow either device to control the reference.

SDIFS

SDI

Operating Modes

There are three main modes of operation available on the

AD73322L; Program, Data and Mixed Program/Data modes.

Two other operating modes are typically reserved as diagnostic

modes: Digital and SPORT Loop-Back. The device configura-

tion—register settings—can be changed only in Program and

Mixed Program/Data Modes. In all modes, transfers of informa-

tion to or from the device occur in 16-bit packets, therefore the

DSP engine’s SPORT will be programmed for 16-bit transfers.

CONTROL WORD (DEVICE 2)

CONTROL WORD (DEVICE 1)

Figure 11. Interface Signal Timing for Control Mode

Operation

Data Mode

Once the device has been configured by programming the cor-

rect settings to the various control registers, the device may exit

Program Mode and enter Data Mode. This is done by program-

ming the DATA/PGM (CRA:0) bit to a 1 and MM (CRA:1) to

0. Once the device is in Data Mode, the 16-bit input data frame

is now interpreted as DAC data rather than a control frame. This

data is therefore loaded directly to the DAC register. In Data

Mode, see Figure 12, as the entire input data frame contains

DAC data, the device relies on counting the number of input

frame syncs received at the SDIFS pin. When that number

equals the device count stored in the device count field of CRA,

the device knows that the present data frame being received is

its own DAC update data. When the device is in normal Data

Mode (i.e., mixed mode disabled), it must receive a hardware

reset to reprogram any of the control register settings.

Program (Control) Mode

In Program Mode, CRA:0 = 0, the user writes to the control

registers to set up the device for desired operation—SPORT

operation, cascade length, power management, input/output

gain, etc. In this mode, the 16-bit information packet sent to the

device by the DSP engine is interpreted as a control word whose

format is shown in Table XII. In this mode, the user must address

the device to be programmed using the address field of the control

word. This field is read by the device and if it is zero (000 bin), the

device recognizes the word as being addressed to it. If the address

field is not zero, it is then decremented and the control word is

REV. 0

–21–

AD73322L

Digital Loop-Back

In a single AD73322L configuration, each 16-bit data frame

sent from the DSP to the device is interpreted as DAC data, but

it is necessary to send two DAC words per sample period in

order to ensure DAC update. Also, as the device count setting

defaults to 1, it must be set to 2 (001b) to ensure correct update

of both DACs on the AD73322L.

This mode can be used for diagnostic purposes and allows the

user to feed the ADC samples from the ADC register directly to

the DAC register. This forms a loop-back of the analog input to

the analog output by reconstructing the encoded signal using

the decoder channel. The serial interface will continue to work,

which allows the user to control gain settings, etc. Only when

DLB is enabled with mixed mode operation can the user disable

the DLB, otherwise the device must be reset.

Appendix B details the initialization and operation of an

AD73322L in normal Data Mode.

SPORT Loop-Back

SE

This mode allows the user to verify the DSP interfacing and

connection by writing words to the SPORT of the devices and

have them returned back unchanged after a delay of 16 SCLK

cycles. The frame sync and data word that are sent to the device

are returned via the output port. Again, SLB mode can only be

disabled when used in conjunction with mixed mode, otherwise

the device must be reset.

SCLK

SDOFS

ADC SAMPLE WORD (DEVICE 2)

ADC SAMPLE WORD (DEVICE 1)

SDO

Analog Loop-Back

In Analog Loop-Back mode, the differential DAC output is

connected, via a loop-back switch, to the ADC input (see Figure

13). This mode allows the ADC channel to check functionality

of the DAC channel as the reconstructed output signal can be

monitored using the ADC as a sampler. Analog Loop-Back is

enabled by setting the ALB bit (CRF:7).

SDIFS

SDI

DAC DATA WORD (DEVICE 2)

DAC DATA WORD (DEVICE 1)

Figure 12. Interface Signal Timing for Data Mode

Operation

NOTE: Analog Loop-Back can only be enabled if the Analog

Gain Tap is powered down (CRC:1 = 0).

Mixed Program/Data Mode

This mode allows the user to send control words to the device

along with the DAC data. This permits adaptive control of the

device whereby control of the input/output gains etc., can be

affected by interleaving control words along with the normal

flow of DAC data. The standard data frame remains 16 bits,

but now the MSB is used as a flag bit to indicate whether the

remaining 15 bits of the frame represent DAC data or control

information. In the case of DAC data, the 15 bits are loaded

with MSB justification and LSB set to 0 to the DAC register.

Mixed mode is enabled by setting the MM bit (CRA:1) to 1 and

the DATA/PGM bit (CRA:0) to 1. In the case where control

setting changes will be required during normal operation, this

mode allows the ability to load both control and data informa-

tion with the slight inconvenience of formatting the data. Note

that the output samples from the ADC will also have the MSB

set to zero to indicate it is a data word.

ANALOG

LOOP-BACK

SELECT

SINGLE-

ENDED

INVERTING

OP AMPS

INVERT

ENABLE

VFBN1

VINN1

0/38dB

PGA

V

REF

VINP1

V

REF

VFBP1

GAIN

ꢂ1

ANALOG GAIN

TAP POWERED

DOWN

VOUTP1

VOUTN1

CONTINUOUS

TIME

LOW-PASS

FILTER

+6/–15dB

PGA

Appendix C details the initialization and operation of an

AD73322L operating in mixed mode. Note that it is not essen-

tial to load the control registers in Program Mode before setting

mixed mode active. It is also possible to initiate mixed mode by

programming CRA with the first control word and then inter-

leaving control words with DAC data.

AD73322L

REFOUT

REFCAP

REFERENCE

Figure 13. Analog Loop-Back Connectivity

–22–

REV. 0

AD73322L

INTERFACING

Cascade Operation

The AD73322L can be interfaced to most modern DSP engines

using conventional serial port connections and an extra enable

control line. Both serial input and output data use an accompa-

nying frame synchronization signal that is active high one clock

cycle before the start of the 16-bit word or during the last bit of

the previous word if transmission is continuous. The serial clock

(SCLK) is an output from the codec and is used to define the

serial transfer rate to the DSP’s Tx and Rx ports. Two primary

configurations can be used: the first is shown in Figure 14 where

the DSP’s Tx data, Tx frame sync, Rx data and Rx frame sync

are connected to the codec’s SDI, SDIFS, SDO and SDOFS

respectively. This configuration, referred to as indirectly coupled or

nonframe sync loop-back, has the effect of decoupling the trans-

mission of input data from the receipt of output data. The delay

between receipt of codec output data and transmission of input

data for the codec is determined by the DSP’s software latency.

The AD73322L has been designed to support cascading of

codecs from a single DSP serial port (see Figure 27). Cascaded

operation can support mixes of dual or single channel devices

with the maximum number of codec units being eight (the

AD73322L is equivalent to two codec units). The SPORT

interface protocol has been designed so that device addressing is

built into the packet of information sent to the device. This

allows the cascade to be formed with no extra hardware over-

head for control signals or addressing. A cascade can be formed

in either of the two modes previously discussed.

There may be some restrictions in cascade operation due to the

number of devices configured in the cascade and the sampling

rate and serial clock rate chosen. The following relationship

details the restrictions in configuring a codec cascade.

Number of Codecs × Word Size (16) × Sampling Rate <= Serial

Clock Rate

When programming the DSP serial port for this configuration, it

is necessary to set the Rx FS as an input and the Tx FS as an

output generated by the DSP. This configuration is most useful

when operating in mixed mode, as the DSP has the ability to

decide how many words (either DAC or control) can be sent to

the codecs. This means that full control can be implemented

over the device configuration as well as updating the DAC in a

given sample interval.

SDIFS

SDI

TFS

DT

CODEC1

CODEC2

ADSP-21xx

DSP

SCLK

AD73322L

CODEC

DR

SDO

The second configuration (shown in Figure 15) has the DSP’s

Tx data and Rx data connected to the codec’s SDI and SDO,

respectively, while the DSP’s Tx and Rx frame syncs are con-

nected to the codec’s SDIFS and SDOFS. In this configuration,

referred to as directly coupled or frame sync loop-back, the frame

sync signals are connected together and the input data to the

codec is forced to be synchronous with the output data from the

codec. The DSP must be programmed so that both the Tx FS

and Rx FS are inputs as the codec SDOFS will be input to both.

This configuration guarantees that input and output events occur

simultaneously and is the simplest configuration for operation in

normal Data Mode. Note that when programming the DSP in

this configuration it is advisable to preload the Tx register with

the first control word to be sent before the codec is taken out

of reset. This ensures that this word will be transmitted to coin-

cide with the first output word from the device(s).

RFS

SDOFS

Figure 15. Directly Coupled or Frame Sync Loop-

Back Configuration

When using the indirectly coupled frame sync configuration in

cascaded operation, it is necessary to be aware of the restrictions

in sending data to all devices in the cascade. Effectively the time

allowed is given by the sampling interval (M/DMCLK—where

M can be one of 256, 512, 1024 or 2048), which is 125 µs for a

sample rate of 8 kHz. In this interval, the DSP must transfer

N × 16 bits of information where N is the number of devices in

the cascade. Each bit will take 1/SCLK and, allowing for any

latency between the receipt of the Rx interrupt and the trans-

mission of the Tx data, the relationship for successful operation

is given by:

M/DMCLK > ((N × 16/SCLK) + T_{INTERRUPT LATENCY}

)

SDIFS

SDI

TFS

DT

The interrupt latency will include the time between the ADC

sampling event and the Rx interrupt being generated in the

DSP—this should be 16 SCLK cycles.

CODEC1

CODEC2

ADSP-21xx

DSP

SCLK

AD73322L

CODEC

As the AD73322L is configured in cascade mode, each device

must know the number of devices in the cascade because the

data and mixed modes use a method of counting input frame

sync pulses to decide when they should update the DAC register

from the serial input register. Control Register A contains a 3-bit

field (DC0-2) that is programmed by the DSP during the pro-

gramming phase. The default condition is that the field contains

000b, which is equivalent to a single device in cascade (see

Table XXI). However, for cascade operation this field must

contain a binary value that is one less than the number of

devices in the cascade, which is 001b for a single AD73322L

device configuration.

DR

SDO

RFS

SDOFS

Figure 14. Indirectly Coupled or Nonframe Sync Loop-

Back Configuration

REV. 0

–23–

AD73322L

0

Table XXI. Device Count Settings

–20

DC2

DC1

DC0

Cascade Length

0

1

0

1

0

1

0

1

0

1

0

1

0

1

2

3

4

5

6

7

8

–40

–60

–80

–100

–120

–140

PERFORMANCE

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4

As the AD73322L is designed to provide high performance, low

cost conversion, it is important to understand the means by

which this high performance can be achieved in a typical appli-

cation. This section will, by means of spectral graphs, outline

the typical performance of the device and highlight some of the

options available to users in achieving their desired sample rate,

either directly in the device or by doing some post-processing in

the DSP, while also showing the advantages and disadvantages

of the different approaches.

ꢃ 10

FREQUENCY – Hz

Figure 16. FFT (ADC 64 kHz Sampling)

0

–20

–40

Encoder Section

The AD73322L offers a variable sampling rate from a fixed

MCLK frequency—with 64 kHz, 32 kHz, 16 kHz and 8 kHz

being available with a 16.384 MHz external clock. Each of these

sampling rates preserves the same sampling rate in the ADC’s

sigma-delta modulator, which ensures that the noise perfor-

mance is optimized in each case. The examples below will show

the performance of a 1 kHz sine wave when converted at the

various sample rates.

–60

–80

–100

–120

0

500

1000 1500 2000 2500

3000 3500 4000

FREQUENCY – Hz

The range of sampling rates is aimed to offer the user a degree

of flexibility in deciding how their analog front end is to be

implemented. The high sample rates of 64 kHz and 32 kHz are

suited to those applications, such as active control, where low

conversion group delay is essential. On the other hand, the lower

sample rates of 16 kHz and 8 kHz are better suited for appli-

cations such as telephony, where the lower sample rates result

in lower DSP overhead.

Figure 17. FFT (ADC 8 kHz Filtered and Decimated from

64 kHz)

The AD73322L also features direct sampling at the lower rate

of 8 kHz. This is achieved by the use of extended decimation

registers within the decimator block, which allows for the

increased word growth associated with the higher effective

oversampling ratio. Figure 18 details the spectrum of a 1 kHz

test tone converted at an 8 kHz rate.

Figure 20 shows the spectrum of the 1 kHz test tone sampled at

64 kHz. The plot shows the characteristic shaped noise floor of

a sigma-delta converter, which is initially flat in the band of

interest but then rises with increasing frequency. If a suitable

digital filter is applied to this spectrum, it is possible to eliminate

the noise floor in the higher frequencies. This signal can then be

used in DSP algorithms or can be further processed in a deci-

mation algorithm to reduce the effective sample rate. Figure 17

shows the resulting spectrum following the filtering and decima-

tion of the spectrum of Figure 16 from 64 kHz to an 8 kHz rate.

0

50

100

150

0

500

1000

1500

2000

2500 3000

3500

4000

FREQUENCY – Hz

Figure 18. FFT (ADC 8 kHz Direct Sampling)

–24–

REV. 0

AD73322L

Encoder Group Delay

The device features an on-chip master clock divider circuit that

allows the sample rate to be reduced as the sampling rate of the

sigma-delta converter is proportional to the output of the MCLK

Divider (whose default state is divide-by-one).

When programmed for high sampling rates, the AD73322L

offers a very low level of group delay, which is given by the

following relationship:

Group Delay (Decimator) = Order × ((M – 1)/2) × T_DEC

where:

The decimator’s frequency response (Sinc3) gives some pass-

band attenuation (up to F_S/2) which continues to roll off above

the Nyquist frequency. If it is required to implement a digital

filter to create a sharper cutoff characteristic, it may be prudent

to use an initial sample rate of greater than twice the Nyquist

rate in order to avoid aliasing due to the smooth roll-off of the

Sinc3 filter response.

Order is the order of the decimator (= 3),

M is the decimation factor (= 32 @ 64 kHz, = 64 @ 32 kHz,

= 128 @ 16 kHz , = 256 @ 8 kHz) and

T_DECis the decimation sample interval (= 1/2.048e6) (based

In the case of voiceband processing where 4 kHz represents the

Nyquist frequency, if the signal to be measured were externally

bandlimited then an 8 kHz sampling rate would suffice. How-

ever if it is required to limit the bandwidth using a digital filter,

then it may be more appropriate to use an initial sampling rate

of 16 kHz and to process this sample stream with a filtering and

decimating algorithm to achieve a 4 kHz bandlimited signal at

an 8 kHz rate. Figure 19 details the initial 16 kHz sampled tone.

on DMCLK = 16.384 MHz) => Group Delay (Decimator @

64 kHz) = 3 × (32 – 1)/2 × (1/2.048e6) = 22.7 µs

If final filtering is implemented in the DSP, the final filter’s

group delay must be taken into account when calculating overall

group delay.

Decoder Section

The decoder section updates (samples) at the same rate as the

encoder section. This rate is programmable as 64 kHz, 32 kHz,

16 kHz or 8 kHz (from a 16.384 MHz MCLK). The decoder

section represents a reverse of the process that was described in

the encoder section. In the case of the decoder section, signals

are applied in the form of samples at an initial low rate. This

sample rate is then increased to the final digital sigma-delta

modulator rate of DMCLK/8 by interpolating new samples

between the original samples. The interpolating filter also has the

action of canceling images due to the interpolation process using

spectral nulls that exist at integer multiples of the initial sampling

rate. Figure 21 shows the spectral response of the decoder section

sampling at 64 kHz. Again, its sigma-delta modulator shapes the

noise so it is reduced in the voice bandwidth dc–4 kHz. For

improved voiceband SNR, the user can implement an initial

anti-imaging filter, preceded by 8 kHz to 64 kHz interpolation,

in the DSP.

0

–20

–40

–60

–80

–100

–120

–140

0

1000

2000

3000

4000

5000 6000

7000

8000

FREQUENCY – Hz

Figure 19. FFT (ADC 16 kHz Direct Sampling)

0

–10

Figure 20 details the spectrum of the final 8 kHz sampled fil-

tered tone.

–20

–30

–40

–50

–60

–70

–80

0

–20

–40

–60

–80

–90

–100

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4

–100

–120

–140

FREQUENCY – Hz

ꢃ 10

Figure 21. FFT (DAC 64 kHz Sampling)

0

500

1000

1500

2000

2500 3000

3500

4000

FREQUENCY – Hz

Figure 20. FFT (ADC 8 kHz Filtered and Decimated from

16 kHz)

REV. 0

–25–

AD73322L

Decoder Group Delay

As the AD73322L can be operated at 8 kHz (see Figure 22) or

16 kHz sampling rates, which make it particularly suited for voice-

band processing, it is important to understand the action of the

interpolator’s Sinc3 response. As was the case with the encoder

section, if the output signal’s frequency response is not bounded

by the Nyquist frequency, it may be necessary to perform some

initial digital filtering to eliminate signal energy above Nyquist

to ensure that it is not imaged at the integer multiples of the

sampling frequency. If the user chooses to bypass the interpo-

lator, perhaps to reduce group delay, images of the original

signal will be generated at integer intervals of the sampling fre-

quency. In this case these images must be removed by external

analog filtering.

The interpolator roll-off is mainly due to its sinc-cubed function

characteristic, which has an inherent group delay given by the

equation:

Group Delay (Interpolator) = Order × (L – 1)/2) × T_INT

where:

Order is the interpolator order (= 3),

L is the interpolation factor (= 32 @ 64 kHz, = 64 @ 32 kHz,

= 128 @ 16 kHz, = 256 @ 8 kHz) and

T

_INTis the interpolation sample interval (= 1/2.048e6)

=> Group Delay (Interpolator @ 64 kHz)

= 3 × (32 – 1)/2 × (1/2.048e6)

0

–10

–20

–30

–40

= 22.7 µs

The analog section has a group delay of approximately 25 µs.

On-Chip Filtering

The primary function of the system filtering’s sinc-cubed (Sinc3)

response is to eliminate aliases or images of the ADCs or DAC’s

resampling, respectively. Both modulators are sampled at a nomi-

nal rate of DMCLK/8 (which is 2.048 MHz for a DMCLK of

16.384 MHz) and the simple, external RC antialias filter is

sufficient to provide the required stopband rejection above the

Nyquist frequency for this sample rate. In the case of the ADC

section, the decimating filter is required to both decrease sample

rate and increase sample resolution. The process of changing

sample rate (resampling) leads to aliases of the original sampled

waveform appearing at integer multiples of the new sample rate.

These aliases would get mapped into the required signal pass-

band without the application of some further antialias filtering.

In the AD73322L, the sinc-cubed response of the decimating

filter creates spectral nulls at integer multiples of the new sample

rate. These nulls coincide with the aliases of the original waveform

which were created by the down-sampling process, therefore

reducing or eliminating the aliasing due to sample rate reduction.

–50

–60

–70

–80

–90

–100

0

500

1000

1500

2000

2500 3000

3500

4000

FREQUENCY – Hz

Figure 22. FFT (DAC 8 kHz Sampling)

Figure 23 shows the output spectrum of a 1 kHz tone being gener-

ated at an 8 kHz sampling rate with the interpolator bypassed.

0

–10

–20

–30

In the DAC section, increasing the sampling rate by interpola-

tion creates images of the original waveform at intervals of the

original sampling frequency. These images may be sufficiently

rejected by external circuitry but the sinc-cubed filter in the

interpolator again nulls the output spectrum at integer intervals

of the original sampling rate which corresponds with the images

due to the interpolation process.

–40

–50

–60

–70

–80

The spectral response of a sinc-cubed filter shows the character-

istic nulls at integer intervals of the sampling frequency. Its

passband characteristic (up to Nyquist frequency) features a

roll-off that continues up to the sampling frequency, where the

first null occurs. In many applications this smooth response will

not give sufficient attenuation of frequencies outside the band of

interest; therefore, it may be necessary to implement a final filter

in the DSP which will equalize the passband roll-off and provide

a sharper transition band and greater stopband attenuation.

–90

–100

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4

FREQUENCY – Hz

ꢃ 10

Figure 23. FFT (DAC 8 kHz Sampling—Interpolator

Bypassed)

–26–

REV. 0

AD73322L

DESIGN CONSIDERATIONS

frequency of the sigma-delta modulator’s sampling rate (typi-

cally 2.048 MHz). It may still require a more specific digital filter

implementation in the DSP to provide the final signal frequency

response characteristics. It is recommended that for optimum

performance that the capacitors used for the antialiasing filter be

of high quality dielectric (NPO). The second issue mentioned

above is interfacing the signal source to the ADC’s switched

capacitor input load. The SC input presents a complex dynamic

load to a signal source, therefore, it is important to understand

that the slew rate characteristic is an important consideration

when choosing external buffers for use with the AD73322L.

The internal inverting op amps on the AD73322L are specifi-

cally designed to interface to the ADC’s SC input stage.

The AD73322L features both differential inputs and outputs on

each channel to provide optimal performance and avoid com-

mon mode noise. It is also possible to interface either inputs or

outputs in single-ended mode. This section details the choice of

input and output configurations and also gives some tips towards

successful configuration of the analog interface sections.

ANTI-ALIAS

FILTER

100ꢄ

VFBN1

VINN1

0.047ꢀF

V

REF

0/38dB

PGA

0.047ꢀF

100ꢄ

VINP1

V

REF

VFBP1

The AD73322L’s on-chip 38 dB preamplifier can be enabled

when there is not enough gain in the input circuit; the preampli-

fier is configured by bits IGS0-2 of CRD. The total gain must

be configured to ensure that a full-scale input signal produces a

signal level at the input to the sigma-delta modulator of the

ADC that does not exceed the maximum input range.

GAIN

ꢂ1

VOUTP1

VOUTN1

CONTINUOUS

TIME

+6/–15dB

PGA

LOW-PASS

FILTER

REFOUT

AD73322L

The dc biasing of the analog input signal is accomplished with

an on-chip voltage reference. If the input signal is not biased at

the internal reference level (via REFOUT), then it must be

ac-coupled with external coupling capacitors. C_INshould be

0.1 µF or larger. The dc biasing of the input can then be accom-

plished using resistors to REFOUT as in Figures 27 and 28.

REFERENCE

REFCAP

0.1ꢀF

Figure 24. Analog Input (DC-Coupled)

Analog Inputs

There are several different ways in which the analog input

(encoder) section of the AD73322L can be interfaced to exter-

nal circuitry. It provides optional input amplifiers which allows

sources with high source impedance to drive the ADC section

correctly. When the input amplifiers are enabled, the input channel

is configured as a differential pair of inverting amplifiers referenced

to the internal reference (REFCAP) level. The inverting termi-

nals of the input amplifier pair are designated as pins VINP1 and

VINN1 for Channel 1 (VINP2 and VINN2 for Channel 2) and

the amplifier feedback connections are available on pins VFBP1

and VFBN1 for Channel 1 (VFBP2 and VFBN2 for Channel 2).

ANTI-ALIAS

FILTER

VFBN1

100ꢄ

VINN1

0.047

ꢀF

V

REF

0/38dB

PGA

0.047

ꢀF

100ꢄ

VINP1

VFBP1

V

REF

GAIN

ꢂ1

VOUTP1

VOUTN1

REFOUT

CONTINUOUS

TIME

LOW-PASS

FILTER

+6/–15dB

PGA

OPTIONAL

BUFFER

For applications where external signal buffering is required,

the input amplifiers can be bypassed and the ADC driven

directly. When the input amplifiers are disabled, the sigma-

delta modulator’s input section (SC PGA) is accessed directly

through the VFBP1 and VFBN1 pins for Channel 1 (VFBP2

and VFBN2 for Channel 2).

AD73322L

REFERENCE

REFCAP

0.1ꢀF

Figure 25. Analog Input (DC-Coupled) Using External

Amplifiers

It is also possible to drive the ADCs in either differential or

single-ended modes. If the single-ended mode is chosen it is

possible using software control to multiplex between two single-

ended inputs connected to the positive and negative input pins.

The AD73322L’s ADC inputs are biased about the internal

reference level (REFCAP level); therefore, it may be necessary to

bias external signals to this level using the buffered REFOUT

level as the reference. This is applicable in either dc- or ac-coupled

configurations. In the case of dc coupling, the signal (biased to

REFOUT) may be applied directly to the inputs (using ampli-

fier bypass), as shown in Figure 24, or it may be conditioned in

an external op amp where it can also be biased to the reference

level using the buffered REFOUT signal, as shown in Figure

25, or it is possible to connect inputs directly to the AD73322L’s

input op amps as shown in Figure 26.

The primary concerns in interfacing to the ADC are first to

provide adequate antialias filtering and to ensure that the signal

source will drive the switched-capacitor input of the ADC

correctly. The sigma-delta design of the ADC and its over sam-

pling characteristics simplify the antialias requirements but it

must be remembered that the single pole RC filter is primarily

intended to eliminate aliasing of frequencies above the Nyquist

REV. 0

–27–

AD73322L

100pF

0.1ꢀF

10kꢄ

100ꢄ

VFBN1

VINN1

50kꢄ

VFBN1

VINN1

0.047

ꢀF

V

REF

0/38dB

PGA

V

REF

0/38dB

PGA

VINP1

50kꢄ

VINP1

V

REF

VFBP1

GAIN

V

REF

ꢂ1

GAIN

ꢂ1

100pF

VOUTP1

VOUTN1

REFOUT

CONTINUOUS

TIME

LOW-PASS

FILTER

+6/–15dB

PGA

VOUTP1

VOUTN1

CONTINUOUS

TIME

LOW-PASS

FILTER

+6/–15dB

PGA

AD73322L

REFERENCE

REFOUT

AD73322L

REFERENCE

REFCAP

0.1ꢀF

Figure 28. Analog Input (AC-Coupled) Single-Ended

Figure 26. Analog Input (DC-Coupled) Using Internal

Amplifiers

If best performance is required from a single-ended source, it

is possible to configure the AD73322L’s input amplifiers as a

single-ended to differential converter as shown in Figure 29.

In the case of ac coupling, a capacitor is used to couple the

signal to the input of the ADC. The ADC input must be biased

to the internal reference (REFCAP) level which is done by

connecting the input to the REFOUT pin through a 10 kΩ

resistor as shown in Figure 27.

100pF

50kꢄ

VFBN1

VINN1

50kꢄ

V

REF

0/38dB

PGA

0.1ꢀF

100ꢄ

VFBN1

VINP1

50kꢄ

VFBP1

0.047

VINN1

V

REF

ꢀF

10kꢄ

V

REF

GAIN

0/38dB

PGA

ꢂ1

100pF

VINP1

0.1ꢀF

10kꢄ

100ꢄ

0.047

V

REF

VFBP1

CONTINUOUS

VOUTP1

VOUTN1

GAIN

ꢀF

TIME

LOW-PASS

FILTER

ꢂ1

+6/–15dB

PGA

VOUTP1

VOUTN1

REFOUT

CONTINUOUS

REFOUT

AD73322L

REFERENCE

TIME

LOW-PASS

FILTER

+6/–15dB

PGA

REFCAP

0.1ꢀF

AD73322L

REFERENCE

Figure 29. Single-Ended to Differential Conversion On

Analog Input

REFCAP

0.1ꢀF

Interfacing to an Electret Microphone

Figure 27. Analog Input (AC-Coupled) Differential

Figure 30 details an interface for an electret microphone which

may be used in some voice applications. Electret microphones

typically feature a FET amplifier whose output is accessed on

the same lead which supplies power to the microphone; there-

fore this output signal must be capacitively coupled to remove

the power supply (dc) component. In this circuit the AD73322L

input channel is being used in single-ended mode where the

internal inverting amplifier provides suitable gain to scale the

input signal relative to the ADC’s full-scale input range. The

buffered internal reference level at REFOUT is used via an

external buffer to provide power to the electret microphone.

This provides a quiet, stable supply for the microphone. If this

is not a concern, then the microphone can be powered from the

system power supply.

If the ADC is being connected in single-ended mode, the

AD73322L should be programmed for single-ended mode using

the SEEN and INV bits of CRF and the inputs connected as

shown in Figure 28. When operated in single-ended input

mode, the AD73322L can multiplex one of the two inputs to

the ADC input.

–28–

REV. 0

AD73322L

Figure 32 shows an example circuit for providing a single-ended

output with ac coupling. The capacitor of this circuit (C_OUT) is

not optional if dc current drain is to be avoided.

5V

R

A

10ꢀF

C1

R2

VFBN1

VINN1

VFBN1

VINN1

C2

R

B

R1

V

REF

V

REF

VINP1

ELECTRET

PROBE

VFBP1

VINP1

GAIN

0/38dB

PGA

ꢂ1

VFBP1

C

OUT

VOUTP1

CONTINUOUS

V

TIME

LOW-PASS

FILTER

REF

+6/–15dB

PGA

R

LOAD

GAIN

1

VOUTN1

REFOUT

AD73322L

REFERENCE

VOUTP1

REFCAP

CONTINUOUS

TIME

LOW-PASS

FILTER

+6/–15dB

PGA

0.1ꢀF

VOUTN1

REFOUT

REFCAP

Figure 32. Example Circuit for Single-Ended Output

REFERENCE

Differential to Single-Ended Output

In some applications it may be desirable to convert the full

differential output of the decoder channel to a single-ended

signal. The circuit of Figure 33 shows a scheme for doing this.

C

REFCAP

Figure 30. Electret Microphone Interface Circuit

VFBN1

VINN1

Analog Output

The AD73322L’s differential analog output (VOUT) is produced

by an on-chip differential amplifier. The differential output can

be ac-coupled or dc-coupled directly to a load which can be a

headset or the input of an external amplifier (the specified mini-

mum resistive load on the output section is 150 Ω.) It is possible

to connect the outputs in either a differential or a single-ended

configuration but please note that the effective maximum output

voltage swing (peak to peak) is halved in the case of single-ended

connection. Figure 31 shows a simple circuit providing a differen-

V

REF

0/38dB

PGA

VINP1

VFBP1

V

REF

GAIN

ꢂ1

R_F

VOUTP1

VOUTN1

CONTINUOUS

R_I

TIME

LOW-PASS

FILTER

+6/–15dB

PGA

R_F

R

LOAD

REFOUT

tial output with ac coupling. The capacitors in this circuit (C_OUT

)

AD73322L

REFERENCE

are optional; if used, their value can be chosen as follows:

REFCAP

0.1ꢀF

1

C_OUT

=

2π f_CR_LOAD

Figure 33. Example Circuit for Differential to Single-

Ended Output Conversion

where f_C= desired cutoff frequency.

Digital Interfacing

The AD73322L is designed to easily interface to most common

DSPs. The SCLK, SDO, SDOFS, SDI and SDIFS must be

connected to the DSP’s Serial Clock, Receive Data, Receive

Data Frame Sync, Transmit Data and Transmit Data Frame

Sync pins respectively. The SE pin may be controlled from a

parallel output pin or flag pin such as FL0-2 on the ADSP-21xx

(or XF on the TMS320C5x) or, where SPORT power-down is not

required, it can be permanently strapped high using a suitable

pull-up resistor. The RESET pin may be connected to the sys-

tem hardware reset structure or it may also be controlled using a

dedicated control line. In the event of tying it to the global sys-

tem reset, it is advisable to operate the device in mixed mode,

which allows a software reset, otherwise there is no convenient

way of resetting the device. Figures 34 and 35 show typical

connections to an ADSP-218x and TMS320C5x respectively.

VFBN1

VINN1

V

REF

VINP1

VFBP1

GAIN

ꢂ1

C_OUT

VOUTP1

CONTINUOUS

TIME

LOW-PASS

FILTER

+6/–15dB

PGA

R

LOAD

VOUTN1

C_OUT

REFOUT

REFCAP

AD73322L

REFERENCE

C

REFCAP

Figure 31. Example Circuit for Differential Output

REV. 0

–29–

AD73322L

Connection of a cascade of devices to a DSP, as shown in Fig-

ure 37, is no more complicated than connecting a single device.

Instead of connecting the SDO and SDOFS to the DSP’s Rx

port, these are now daisy-chained to the SDI and SDIFS of the

next device in the cascade. The SDO and SDOFS of the final

device in the cascade are connected to the DSP’s Rx port to

complete the cascade. SE and RESET on all devices are fed

from the signals that were synchronized with the MCLK using

the circuit as described above. The SCLK from only one device

need be connected to the DSP’s SCLK input(s) as all devices

will be running at the same SCLK frequency and phase.

SDIFS

SDI

TFS

DT

SCLK

AD73322L

CODEC

ADSP-218x

DSP

DR

SDO

RFS

SDOFS

FL0

FL1

RESET

SE

Grounding and Layout

Since the analog inputs to the AD73322L are differential, most

of the voltages in the analog modulator are common-mode volt-

ages. The excellent common-mode rejection of the part will

remove common-mode noise on these inputs. The analog and

digital supplies of the AD73322L are independent and separately

pinned out to minimize coupling between analog and digital

sections of the device. The digital filters on the encoder section

will provide rejection of broadband noise on the power supplies,

except at integer multiples of the modulator sampling frequency.

The digital filters also remove noise from the analog inputs

provided the noise source does not saturate the analog modula-

tor. However, because the resolution of the AD73322L’s ADC

is high, and the noise levels from the AD73322L are so low,

care must be taken with regard to grounding and layout.

Figure 34. AD73322L Connected to ADSP-218x

SDIFS

SDI

FSX

DT

CLKX

SCLK

AD73322L

CODEC

TMS320C5x

DSP

CLKR

DR

SDO

FSR

SDOFS

RESET

SE

XF

SDIFS

SDI

TFS

DT

MCLK

SE

Figure 35. AD73322L Connected to TMS320C5x

Cascade Operation

Where it is required to configure a cascade of up to eight codecs

(four AD73322L dual codecs), it is necessary to ensure that the

timing of the SE and RESET signals is synchronized at each

device in the cascade. A simple D type flip flop is sufficient to

sync each signal to the master clock MCLK, as in Figure 36.

AD73322L

CODEC

ADSP-218x

DSP

SCLK

SDO

RESET

DR

DEVICE 1

RFS

SDOFS

FL0

FL1

SDIFS

SDI

MCLK

SE

DSP CONTROL

TO SE

SE SIGNAL SYNCHRONIZED

TO MCLK

D

Q

1/2

AD73322L

CODEC

74HC74

RESET

SCLK

SDO

MCLK

CLK

DEVICE 2

SDOFS

DSP CONTROL

TO RESET

RESET SIGNAL SYNCHRONIZED

TO MCLK

D

Q

1/2

74HC74

D1

D2 74HC74

Q1

Q2

MCLK

CLK

Figure 36. SE and RESET Sync Circuit for Cascaded

Operation

Figure 37. Connection of Two AD73322Ls Cascaded to

ADSP-218x

–30–

REV. 0

AD73322L

DSP SPORT Configuration

Following are the key settings of the DSP SPORT required for

the successful operation with the AD73322L:

The printed circuit board that houses the AD73322L should be

designed so the analog and digital sections are separated and

confined to certain sections of the board. The AD73322L pin

configuration offers a major advantage in that its analog and

digital interfaces are connected on opposite sides of the package.

This facilitates the use of ground planes that can be easily sepa-

rated, as shown in Figure 38. A minimum etch technique is

generally best for ground planes as it gives the best shielding.

Digital and analog ground planes should be joined in only one

place. If this connection is close to the device, it is recommended

to use a ferrite bead inductor as shown in Figure 38.

• Configure for External SCLK.

• Serial Word Length = 16 bits.

• Transmit and Receive Frame Syncs required with every word.

• Receive Frame Sync is an input to the DSP.

• Transmit Frame Sync is an:

Input—in Frame Sync Loop-Back Mode

Output—in Nonframe Sync Loop-Back Mode.

• Frame Syncs occur one SCLK cycle before the MSB of the

DIGITAL GROUND

serial word.

• Frame Syncs are active high.

DSP SPORT Interrupts

If SPORT interrupts are enabled, it is important to note that the

active signals on the frame sync pins do not necessarily corre-

spond with the positions in time of where SPORT interrupts

are generated.

ANALOG GROUND

Figure 38. Ground Plane Layout

On ADSP-21xx processors, it is necessary to enable SPORT

interrupts and use Interrupt Service Routines (ISRs) to handle

Tx/Rx activity, while on the TMS320CSx processors it is pos-

sible to poll the status of the Rx and Tx registers, which means

that Rx/Tx activity can be monitored using a single ISR that

would ideally be the Tx ISR as the Tx interrupt will typically

occur before the Rx ISR.

Avoid running digital lines under the device for they will couple

noise onto the die. The analog ground plane should be allowed

to run under the AD73322L to avoid noise coupling. The power

supply lines to the AD73322L should use as large a trace as

possible to provide low impedance paths and reduce the effects

of glitches on the power supply lines. Fast switching signals such

as clocks should be shielded with digital ground to avoid radiat-

ing noise to other sections of the board, and clock signals should

never be run near the analog inputs. Traces on opposite sides of

the board should run at right angles to each other. This will

reduce the effects of feedthrough through the board. A microstrip

technique is by far the best but is not always possible with a

double-sided board. In this technique, the component side of

the board is dedicated to ground planes while signals are placed

on the other side.

DSP SOFTWARE CONSIDERATIONS WHEN

INTERFACING TO THE AD73322L

It is important when choosing the operating mode and hardware

configuration of the AD73322L to be aware of their implica-

tions for DSP software operation. The user has the flexibility

of choosing from either FSLB or NonFSLB when deciding on

DSP to AFE connectivity. There is also a choice to be made

between using autobuffering of input and output samples or

simply choosing to accept them as individual interrupts. As

most modern DSP engines support these modes, this appendix

will attempt to discuss these topics in a generic DSP sense.

Good decoupling is important when using high speed devices.

On the AD73322L both the reference (REFCAP) and supplies

need to be decoupled. It is recommended that the decoupling

capacitors used on both REFCAP and the supplies, be placed as

close as possible to their respective pins to ensure high perfor-

mance from the device. All analog and digital supplies should be

decoupled to AGND and DGND respectively, with 0.1 µF

ceramic capacitors in parallel with 10 µF tantalum capacitors.

In systems where a common supply voltage is used to drive both

the AVDD and DVDD of the AD73322L, it is recommended

that the system’s AVDD supply be used. This supply should

have the recommended analog supply decoupling between the

AVDD pins of the AD73322L and AGND and the recom-

mended digital supply decoupling capacitors between the DVDD

pin and DGND.

Operating Mode

The AD73322L supports two basic operating modes: Frame Sync

Loop Back (FSLB) and NonFSLB (See Interfacing section). As

described previously, FSLB has some limitations when used in

Mixed Mode but is very suitable for use with the autobuffering

feature that is offered on many modern DSPs. Autobuffering

allows the user to specify the number of input or output words

(samples) that are transferred before a specific Tx or Rx SPORT

interrupt is generated. Given that the AD73322L outputs two

sample words per sample period, it is possible using autobuffer-

ing to have the DSP’s SPORT generate a single interrupt on

receipt of the second of the two sample words. Additionally,

both samples could be stored in a data buffer within the data

memory store. This technique has the advantage of reducing the

number of both Tx and Rx SPORT interrupts to a single one at

each sample interval. The user also knows where each sample

is stored. The alternative is to handle a larger number of SPORT

interrupts (twice as many in the case of a single AD73322L)

while also having some status flags to indicate where each new

sample comes from (or is destined for).

DSP PROGRAMMING CONSIDERATIONS

This section discusses some aspects of how the serial port of the

DSP should be configured and the implications of whether Rx

and Tx interrupts should be enabled.

REV. 0

–31–

AD73322L

Mixed-Mode Operation

Running the AD73322L with ADCs or DACs in Power-Down

The programmability of the AD73322L allows the user flex-

ibility in choosing what sections of the AD73322L need be

powered up. This allows better matching of the power con-

sumption to the application requirements as the AD73322L

offers two ADCs and two DACs in any combination. The

AD73322L always interfaces to the DSP in a standard way

regardless of what ADC or DAC sections are enabled or disabled.

Therefore the DSP will expect to receive two ADC samples per

sample period and to transmit two DAC samples per sample

period. If a particular ADC is disabled (in power-down) then its

sample value will be invalid. Likewise a sample sent to a DAC

which is disabled will have no effect.

To take full advantage of mixed-mode operation, it is necessary

to configure the DSP/Codec interface in NonFSLB and to disable

autobuffering. This allows a variable numbers of words to be

sent to the AD73322L in each sample period—the extra words

being control words that are typically used to update gain settings

in adaptive control applications. The recommended sequence

for updating control registers in mixed mode is to send the

control word(s) first before the DAC update word.

It is possible to use mixed-mode operation when configured in

FSLB, but it is necessary to replace the DAC update with a

control word write in each sample period which may cause some

discontinuity in the output signal due to a sample point being

missed and the previous sample being repeated. This however

may be acceptable in some cases as the effect may be masked by

gain changes, etc.

There are two distinct phases of operation of the AD73322L:

initialization of the device via each codec section’s control regis-

ters, and operation of the converter sections of each codec. The

initialization phase involves programming the control registers

of the AD73322L to ensure the required operating characteristics

such as sampling rate, serial clock rate, I/O gain, etc. There are

several ways in which the DSP can be programmed to initialize

the AD73322L. These range from hard-coding a sequence of

DSP SPORT Tx register writes with constants used for the

initialization words, to putting the initialization sequence in a

circular data buffer and using an autobuffered transmit sequence.

Interrupts

The AD73322L transfers and receives information over the serial

connection from the DSP’s SPORT. This occurs following reset

—during the initialization phase—and in both data-mode and

mixed-mode. Each transfer of data to or from the DSP can

cause a SPORT interrupt to occur. However even in FSLB

configuration where serial transfers in and out of the DSP are

synchronous, it is important to note that Tx and Rx interrupts

do not occur at the same time due to the way that Tx and Rx

interrupts are generated internally within the DSP’s SPORT.

This is especially important in time critical control loop applica-

tions where it may be necessary to use Rx interrupts only, as the

relative positioning of the Tx interrupts relative to the Rx inter-

rupts in a single sample interval are not suitable for quick update of

new DAC positions.

Hard-coding involves creating a sequence of writes to the DSP’s

SPORT Tx buffer which are separated by loops or instructions

that idle and wait for the next Tx interrupt to occur as shown in

the code below.

ax0

tx0

= b#1000100100000100;

= ax0;

idle; {wait for tx register to send current word}

Initialization

The circular buffer approach can be useful if a long initialization

sequence is required. The list of initialization words is put into

the buffer in the required order:

Following reset, the AD73322L is in its default condition which

ensures that the device is in Control Mode and must be pro-

grammed or initialized from the DSP to start conversions. As

communications between AD73322L and the DSP are interrupt

driven, it is usually not practical to embed the initialization

codes into the body of the initialization routine. It is more prac-

tical to put the sequence of initialization codes in a data (or

program) memory buffer and to access this buffer with a pointer

that is updated on each interrupt. If a circular buffer is used, it

allows the interrupt routine to check when the circular buffer

pointer has wrapped around—at which point the initialization

sequence is complete.

.VAR/DM/RAM/CIRC init_cmds[16]; {Codec init sequence}

.VAR/DM/RAM stat_flag;

.INIT init_cmds:

b # 1 0 0 0 1 0 0 1 0 0 0 0 0 1 0 0 ,

b # 1 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 ,

b # 1 0 0 0 1 0 1 0 1 1 1 1 1 0 0 1 ,

b # 1 0 0 0 0 0 1 0 1 1 1 1 1 0 0 1 ,

b # 1 0 0 0 1 0 1 1 0 0 0 0 0 0 0 0 ,

b # 1 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 ,

b # 1 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 ,

b # 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 ,

b # 1 0 0 0 1 1 0 1 0 0 0 0 0 0 0 0 ,

b # 1 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 ,

b # 1 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 ,

b # 1 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 ,

b # 1 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 ,

b # 1 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 ,

b # 1 0 0 0 1 0 0 0 0 0 0 1 0 0 0 1 ,

b # 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 ;

In FSLB configurations, a single control word per codec per

sample period is sent to the AD73322L whereas in NonFSLB,

it is possible to initialize the device in a single sample period

provide the SCLK rate is programmed to a high rate. It is also

possible to use autobuffering in which case an interrupt is gen-

erated when the entire initialization sequence has been sent to

the AD73322L.

–32–

REV. 0

AD73322L

and the DSP program initializes pointers to the top of the buffer

i3 = ^init_cmds; l3 = %init_cmds;

check_init:

ax0 = dm (stat_flag);

af = pass ax0;

and puts the first entry in the DSP’s transmit buffer so that it is

available at the first SDOFS pulse.

if ne jump check_init;

As the AD73322L is effectively a cascade of two codec units, it

is important to observe some restrictions in the sequence of

sending initialization words to the two codecs. It is preferable to

send pairs of control words for the corresponding control regis-

ters in each codec, and it is essential to send the control word

for codec 2 before that for codec 1. Control Registers A and

B contain settings, such as sampling rate, serial clock rate, etc.,

which critically require synchronous update in both codecs.

ax0 = dm(i3,m1);

tx0 = ax0;

The DSP’s transmit interrupt is enabled.

imask = b#0001000000;

At each occurrence of an SDOFS pulse, the DSP’s transmit

buffer contents are sent to the SDI pin of the AD73322L. This

also causes a subsequent DSP Tx interrupt which transfers the

initialization word, pointed to by the circular buffer pointer, to

the Tx buffer. The buffer pointer is updated to point to the next

unsent initialization word. When the circular buffer pointer wraps

around, which happens after the last word has been accessed, it

indicates that the initialization phase is complete. This can be done

“manually” in the DSP using a simple address check, or auto-

buffered mode can be used to complete the transfer automatically.

Once the device has been initialized, Control Register A on both

codecs is written with a control word which changes the operat-

ing mode from Program Mode to either data mode or Mixed

Control Data Mode. The device count field which defaults to

000b will have to be programmed to 001b for a single AD73322L

device. In data mode or mixed mode, the main function of the

device is to return ADC samples from both codecs and to accept

DAC words for both codecs. During each sample interval, two

ADC samples will be returned from the device, while in the same

interval two DAC update samples will be sent to the device. In

order to reduce the number of interrupts and to reduce com-

plexity, autobuffering can be used to ensure that only one

interrupt is generated during each sampling interval.

txcdat: ar = dm(stat_flag);

ar = pass ar;

if eq rti;

ena sec_reg;

ax0 = dm (i3, m1);

tx0 = ax0;

ax0 = i3;

ay0 = ^init_cmds;

ar = ax0 - ay0;

if gt rti;

ax0 = 0x00;

dm (stat_flag) = ax0;

rti;

In the main body of the program, the code loops waiting for the

initialization sequence to be completed.

REV. 0

–33–

AD73322L

APPENDIX A

DAC Timing Control Example

may process this information and generate a DAC word to be

sent to the AD73322L. Time t₃marks the beginning of the

sequence of sending the DAC word to the AD73322L. This

sequence ends at time t₄where the DAC register will be updated

from the 16 bits in the AD73322L’s serial register. However,

the DAC will not be updated from the DAC register until time

t₅, which may not be acceptable in certain applications. In order

to reduce this delay and load the DAC at time t₆, the DAC

advance register can be programmed with a suitable setting

corresponding to the required time advance (refer to Table X

for details of DAC Timing Control settings).

The AD73322L’s DAC is loaded from the DAC register con-

tents just before the ADC register contents are loaded to the

serial register (SDOFS going high). This default DAC load

position can be advanced in time to occur earlier with respect to

the SDOFS going high. Figure 45 shows an example of the

ADC unload and DAC load sequence. At time t₁the SDOFS is

raised to indicate that a new ADC word is ready. Following the

SDOFS pulse, 16 bits of ADC data are clocked out on SDO in

the subsequent 16 SCLK cycles finishing at time t₂where the

DSP’s SPORT will have received the 16-bit word. The DSP

SE

SCLK

SDOFS

ADC WORD

SDO

SDIFS

SDI

DAC WORD

DATA REGISTER

UPDATE

DAC LOAD

FROM DAC REGISTER

t₁

t₂

t₃

t₄

t₆

t₅

Figure 39. DAC Timing Control

–34–

REV. 0

AD73322L

Steps 7–9 are similar to Steps 1–3, but instead, program Control

Register A, with a device count field equal to two channels in

cascade and sets the PGM/DATA bit to one to put the channel

in data mode.

APPENDIX B

Configuring an AD73322L to Operate in Data Mode¹

This section describes the typical sequence of control words that

are required to be sent to an AD73322L to set it up for data

mode operation. In this sequence Registers B, C and A are

programmed before the device enters data mode. This descrip-

tion panel refers to Table XXII.

In Step 10, the programming phase is complete and we now

begin actual channel data read and write. The words loaded into

the serial registers of the two channels at the ADC sampling

event now contain valid ADC data and the words written to the

channels from the DSP’s Tx register will now be interpreted as

DAC words. The DSP Tx register contains the DAC word for

Channel 2.

At each sampling event, a pair of SDOFS pulses will be observed

which will cause a pair of control (programming) words to be sent

to the device from the DSP. It is advisable that each pair of control

words should program a single register in each Channel. The

sequence to be followed is Channel 2 followed by Channel 1.

In Step 11, the first DAC word has been transmitted into the

cascade and the ADC word from Channel 2 has been read from

the cascade. The DSP Tx register now contains the DAC word

for Channel 1. As the words being sent to the cascade are now

being interpreted as 16-bit DAC words, the addressing scheme

now changes from one where the address was embedded in the

transmitted word, to one where the serial port now counts the

SDIFS pulses. When the number of SDIFS pulses received

equals the value in the channel count field of Control Register

A, the length of the cascade—each channel updates its DAC

register with the present word in its serial register. In Step 11

each channel has received only one SDIFS pulse; Channel 2

received one SDIFS from the SDOFS of Channel 1 when it sent

its ADC word, and Channel 1 received one SDIFS pulse when

it received the DAC word for Channel 2 from the DSP’s Tx regis-

ter. Therefore, each channel raises its SDOFS line to pass on the

current word in its serial register, and each channel now receives

another SDIFS pulse.

In Step 1, we have the first output sample event following device

reset. The SDOFS signal is raised on both channels²simulta-

neously, which prepares the DSP Rx register to accept the ADC

word from Channel 2, while SDOFS from Channel 1 becomes

an SDIFS to Channel 2. As the SDOFS of Channel 2 is coupled

to the DSP’s TFS and RFS, and to the SDIFS of Channel 1,

this event also forces a new control word to be output from the

DSP Tx register to Channel 1³.

In Step 2, we observe the status of the channels following the

transmission of the first control word. The DSP has received the

output word from Channel 2, while Channel 2 has received the

output word from Channel 1. Channel 1 has received the Con-

trol word destined for Channel 2. At this stage, the SDOFS of

both channels are again raised because Channel 2 has received

Channel 1’s output word, and as it is not a valid control word

addressed to Channel 2, it is passed on to the DSP. Likewise,

Channel 1 has received a control word destined for Channel 2—

address field is not zero—and it decrements the address field of

the control word and passes it on.

Step 12 shows the completion of an ADC read and DAC write

cycle. Following Step 11, each channel has received two SDIFS

pulses that equal the setting of the channel count field in Control

Register A. The DAC register in each channel is now updated

with the contents of the word that accompanied the SDIFS

pulse that satisfied the channel count requirement. The internal

frame sync counter is now reset to zero and will begin counting

for the next DAC update cycle.

Step 3 shows completion of the first series of control word

writes. The DSP has now received both output words and each

channel has received a control word that addresses control regis-

ter B and sets the internal MCLK divider ratio to 1, SCLK rate

to DMCLK/2 and sampling rate to DMCLK/256. Note that

both channels are updated simultaneously as both receive the

addressed control word at the same time. This is an important

factor in cascaded operation as any latency between updating

the SCLK or DMCLK of channels can result in corrupted

operation. This will not happen in the case of an FSLB con-

figuration as shown here, but must be taken into account in a

non-FSLB configuration. One other important observation of

this sequence is that the data words are received and transmitted

in reverse order, i.e., the ADC words are received by the DSP,

Channel 2 first, then Channel 1 and, similarly, the transmit

words from the DSP are sent to Channel 2 first, then to Chan-

nel 1. This ensures that all channels are updated at the same time.

Steps 10–12 are repeated on each sampling event.

NOTES

¹Channel 1 and Channel 2 of the description refer to the two AFE sections of

the AD73322L device.

²The AD73322L is configured as two channels in cascade. The internal cascade

connections between Channels 1 and 2 are detailed in Figure 14. The connec-

tions SDI/SDIFS are inputs to Channel 1 while SDO/SDOFS are outputs from

Channel 2.

³This sequence assumes that the DSP SPORT’s Rx and Tx interrupts are

enabled. It is important to ensure that there is no latency (separation) between

control words in a cascade configuration. This is especially the case when

programming Control Registers A and B as they must be updated synchronously

in each channel.

Steps 4–6 are similar to Steps 1–3, but instead, program Control

Register C to power up the analog sections of the device (ADCs,

DACs, and reference).

REV. 0

–35–

AD73322L

Table XXII. Data Mode Operation

DSP

Tx

AD73322L

Channel 1

AD73322L

Channel 2

DSP

Rx

Step

1

CRB–CH2

1000100100001011

CRB–CH1

1000000100001011

CRC–CH2

OUTPUT CH1

0000000000000000

CRB–CH2

1000100100001011

CRB–CH1

OUTPUT CH2

0000000000000000

OUTPUT CH1

0000000000000000

CRB–CH2

DON’T CARE

xxxxxxxxxxxxxxxx

OUTPUT CH2

0000000000000000

OUTPUT CH1

0000000000000000

2

3

1000101011111001

1000000100001011

4

5

6

CRC–CH2

1000101011111001

CRC–CH1

1000001011111001

CRA–CH2

OUTPUT CH1

1000000100001011

CRC–CH2

1000101011111001

CRC-CH1

OUTPUT CH2

1000000100001011

OUTPUT CH2

1011100100001011

CRC–CH2

DON’T CARE

xxxxxxxxxxxxxxxx

OUTPUT CH2

1011100100001011

OUTPUT CH1

1011000100001011

1000100000010001

1000001011111001

7

8

9

CRA–CH2

1000100000010001

CRA–CH1

1000000000010001

CRB-CH2

OUTPUT CH1

1000001011111001

CRA-CH2

1000100000010001

CRA-CH1

OUTPUT CH2

1000001011111001

OUTPUT CH2

1011101011111001

CRA–CH2

DON’T CARE

xxxxxxxxxxxxxxxx

OUTPUT CH2

1011101011111001

OUTPUT CH1

1011001011111001

0111111111111111

1000000000010001

10

11

12

DAC WORD CH 2

0111111111111111

DAC WORD CH 1

1000000000000000

DON’T CARE

ADC RESULT CH1

????????????????

DAC WORD CH 2

0111111111111111

DAC WORD CH 1

1000000000000000

ADC RESULT CH2

????????????????

ADC RESULT CH1

????????????????

DAC WORD CH 2

0111111111111111

DON’T CARE

xxxxxxxxxxxxxxxx

ADC RESULT CH2

????????????????

ADC RESULT CH1

????????????????

xxxxxxxxxxxxxxxx

–36–

REV. 0

AD73322L

APPENDIX C

interrupt service routine the Tx register is loaded with the con-

trol word for Channel 2. In Steps 9–10, Channels 1 and 2 are

loaded with a control word setting for Control Register B

which programs DMCLK = MCLK, the sampling rate to

DMCLK/256, SCLK = DMCLK/2.

Configuring an AD73322L to Operate in Mixed Mode¹

This section describes a typical sequence of control words that

would be sent to an AD73322L to configure it for operation in

mixed mode. It is not intended to be a definitive initialization

sequence, but will show users the typical input/output events

that occur in the programming and operation phases². This

description panel refers to Table XXIII.

Steps 11–17 are similar to Steps 6–12 except that Control Reg-

ister C is programmed to power up all analog sections (ADC,

DAC, Reference = 2.4 V, REFOUT). In Steps 16–17, DAC words

are sent to the device—both DAC words are necessary as each

channel will only update its DAC when the device has counted a

number of SDIFS pulses, accompanied by DAC words (in mixed-

mode, the MSB = 0), that is equal to the device count field of

Control Register A⁴. As the channels are in mixed mode, the

serial port interrogates the MSB of the 16-bit word sent to

determine whether it contains DAC data or control information.

DAC words should be sent in the sequence Channel 2 followed

by Channel 1.

Steps 1–5 detail the transfer of the control words to Control

Register A, which programs the device for Mixed-Mode opera-

tion. In Step 1, we have the first output sample event following

device reset. The SDOFS signal is simultaneously raised on

both channels, which prepares the DSP Rx register to accept the

ADC word from Channel 2 while SDOFS from Channel 1

becomes an SDIFS to Channel 2. The cascade is configured

as nonFSLB, which means that the DSP has control over what

is transmitted to the cascade³and in this case we will not trans-

mit to the devices until both output words have been received

from the AD73322L.

Steps 11–17 illustrate the implementation of Control Register

update and DAC update in a single sample period. Note that

this combination is not possible in the FSLB configuration³.

In Step 2, we observe the status of the channels following the

reception of the Channel 2 output word. The DSP has received

the ADC word from Channel 2, while Channel 2 has received

the output word from Channel 1. At this stage, the SDOFS of

Channel 2 is again raised because Channel 2 has received Chan-

nel 1’s output word and, as it is not addressed to Channel 2, it

is passed on to the DSP.

Steps 18–25 illustrate a Control Register readback cycle. In Step

22, both channels have received a Control Word that addresses

Control Register C for readback (Bit 14 of the Control Word =

1). When the channels receive the readback request, the register

contents are loaded to the serial registers as shown in Step 23.

SDOFS is raised in both channels, which causes these readback

words to be shifted out toward the DSP. In Step 24, the DSP

has received the Channel 2 readback word while Channel 2 has

received the Channel 1 readback word (note that the address

field in both words has been decremented to 111b). In Step 25,

the DSP has received the Channel 1 readback word (its address

field has been further decremented to 110b).

In Step 3 the DSP has now received both ADC words. Typi-

cally, an interrupt will be generated following reception of the

two output words by the DSP (this involves programming the

DSP to use autobuffered transfers of two words). The transmit

register of the DSP is loaded with the control word destined for

Channel 2. This generates a transmit frame-sync (TFS) that is

input to the SDIFS input of the AD73322L to indicate the start

of transmission.

Steps 26–30 detail an ADC and DAC update cycle using the

nonFSLB configuration. In this case no Control Register update

is required.

In Step 4, Channel 1 now contains the Control Word destined

for Channel 2. The address field is decremented, SDOFS1 is

raised (internally) and the Control word is passed on to Channel

2. The Tx register of the DSP has now been updated with the

Control Word destined for Channel 1 (this can be done using

autobuffering of transmit or by handling transmit interrupts

following each word sent).

NOTES

¹Channel 1 and Channel 2 of the description refer to the two AFE sections of

the AD73322L device.

²This sequence assumes that the DSP SPORT’s Rx and Tx interrupts are enabled.

It is important to ensure there is no latency (separation) between control words in

a cascade configuration. This is especially the case when programming Control

Registers A and B.

³Mixed-mode operation with the FSLB configuration is more restricted in that

the number of words sent to the cascade equals the number of channels in the

cascade, which means that DAC updates may need to be substituted with a

register write or read. Using the FSLB configuration introduces a corruption of

the ADC samples in the sample period following a Control Register write. This

corruption is predictable and can be corrected in the DSP. The ADC word is

treated as a Control Word and the Device Address field is decremented in each

channel that it passes through before being returned to the DSP.

⁴In mixed mode, DAC update is done using the same SDIFS counting scheme

as in normal data mode with the exception that only DAC words (MSB set to

zero) are recognized as being able to increment the frame sync counters.

In Step 5 each channel has received a control word that addresses

Control Register A and sets the device count field equal to two

channels and programs the channels into Mixed Mode—MM

and PGM/DATA set to one.

Following Step 5, the device has been programmed into mixed

mode although none of the analog sections have been powered

up (controlled by Control Register C). Steps 6–10 detail update

of Control Register B in mixed mode. In Steps 6–8, the ADC

samples, which are invalid as the ADC section is not yet powered

up, are transferred to the DSP’s Rx section. In the subsequent

REV. 0

–37–

AD73322L

Table XXIII. Mixed Mode Operation

DSP

Tx

AD73322L

Channel 1

AD73322L

Channel 2

DSP

Rx

Step

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

CRA-CH2

1000101011111001

CRA-CH1

1000000000010011

DON’T CARE

xxxxxxxxxxxxxxxx

OUTPUT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

CRA-CH2

1000100000010011

CRA-CH1

1000000000010011

OUTPUT CH2

0000000000000000

OUTPUT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

CRA-CH2

1000000000010011

DON’T CARE

1

2

3

4

5

xxxxxxxxxxxxxxxx

OUTPUT CH2

0000000000000000

OUTPUT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

CRB-CH2

1000100100001011

CRB-CH1

ADC RESULT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

CRB-CH2

ADC RESULT CH2

0000000000000000

ADC RESULT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

6

xxxxxxxxxxxxxxxx

ADC RESULT CH2

0000000000000000

ADC RESULT CH1

0000000000000000

DON’T CARE

7

8

9

1000000100001011

DON’T CARE

xxxxxxxxxxxxxxxx

1000100100001011

CRB-CH1

1000000100001011

xxxxxxxxxxxxxxxx

CRB-CH2

1000000100001011

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

10

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

CRC-CH2

1000101011111001

ADC RESULT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

ADC RESULT CH2

0000000000000000

ADC RESULT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

CRC-CH2

1000001011111001

DON’T CARE

11

12

13

14

15

16

17

xxxxxxxxxxxxxxxx

ADC RESULT CH2

0000000000000000

ADC RESULT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

CRC-CH2

CRC-CH1

1000001011111001

DAC WORD CH 2

0111111111111111

DAC WORD CH 1

1000000000000000

DON’T CARE

1000101011111001

CRC-CH1

1000001011111001

DAC WORD CH 2

0111111111111111

DAC WORD CH 1

1000000000000000

xxxxxxxxxxxxxxxx

DAC WORD CH 2

0111111111111111

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

CRC-CH2

11001010xxxxxxxx

CRC-CH1

10000010xxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

ADC RESULT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

CRC-CH2

11001010xxxxxxxx

CRC-CH1

10000010xxxxxxxx

READBACK CH 1

1100001011111001

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

ADC RESULT CH2

0000000000000000

ADC RESULT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

18

19

20

21

22

23

24

25

xxxxxxxxxxxxxxxx

ADC RESULT CH2

0000000000000000

ADC RESULT CH1

0000000000000000

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

READBACK CH 2

1111101011111001

READBACK CH 1

1111001011111001

xxxxxxxxxxxxxxxx

CRC-CH2

10000010xxxxxxxx

READBACK CH 2

1100001011111001

READBACK CH 1

1111101011111001

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DAC WORD CH 2

0111111111111111

DAC WORD CH 1

1000000000000000

DON’T CARE

ADC RESULT CH1

????????????????

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DAC WORD CH 2

0111111111111111

DAC WORD CH 1

1000000000000000

ADC RESULT CH2

????????????????

ADC RESULT CH1

????????????????

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

DAC WORD CH 2

0111111111111111

DON’T CARE

26

27

28

29

30

xxxxxxxxxxxxxxxx

ADC RESULT CH2

????????????????

ADC RESULT CH1

????????????????

DON’T CARE

xxxxxxxxxxxxxxxx

DON’T CARE

xxxxxxxxxxxxxxxx

–38–

REV. 0

AD73322L

Topic

Page

Topic

Page

FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

FUNCTIONAL BLOCK DIAGRAM . . . . . . . . . . . . . . . . . 1

GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . 1

SPECIFICATIONS (3 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

TIMING CHARACTERISTICS (3 V) . . . . . . . . . . . . . . . . . 5

Timing Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . 7

ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

PIN CONFIGURATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . 7

PIN FUNCTION DESCRIPTIONS . . . . . . . . . . . . . . . . . . 8

TERMINOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

ABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

TYPICAL PERFORMANCE CHARACTERISTICS . . . . 10

FUNCTIONAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . 11

Encoder Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Programmable Gain Amplifier . . . . . . . . . . . . . . . . . . . . . 11

ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Analog Sigma-Delta Modulator . . . . . . . . . . . . . . . . . . . . 11

Decimation Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

ADC Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Decoder Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

DAC Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Interpolation Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Analog Smoothing Filter and PGA . . . . . . . . . . . . . . . . . 13

Differential Output Amplifiers . . . . . . . . . . . . . . . . . . . . . 13

Voltage Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Analog and Digital Gain Taps . . . . . . . . . . . . . . . . . . . . . 13

Analog Gain Tap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Digital Gain Tap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Serial Port (SPORT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

SPORT Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

SPORT Register Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Master Clock Divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Serial Clock Rate Divider . . . . . . . . . . . . . . . . . . . . . . . . . 16

Sample Rate Divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

DAC Advance Register . . . . . . . . . . . . . . . . . . . . . . . . . . 16

CONTROL REGISTERS . . . . . . . . . . . . . . . . . . . . . . . . 18

OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Resetting the AD73322L . . . . . . . . . . . . . . . . . . . . . . . . . 21

Power Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Program (Control) Mode . . . . . . . . . . . . . . . . . . . . . . . . . 21

Data Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Mixed Program/Data Mode . . . . . . . . . . . . . . . . . . . . . . . 22

Digital Loop-Back . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

SPORT Loop-Back . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Analog Loop-Back . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

INTERFACING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Cascade Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Encoder Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Encoder Group Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Decoder Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Decoder Group Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

On-Chip Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

DESIGN CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . 27

Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Interfacing to an Electret Microphone . . . . . . . . . . . . . . . 28

Analog Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Differential to Single-Ended Output . . . . . . . . . . . . . . . . 29

Digital Interfacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Cascade Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Grounding and Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

DSP PROGRAMMING CONSIDERATIONS . . . . . . . . . 31

DSP SPORT Configuration . . . . . . . . . . . . . . . . . . . . . . . 31

DSP SPORT Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 31

DSP SOFTWARE CONSIDERATIONS WHEN

INTERFACING TO THE AD73322L . . . . . . . . . . . . . . 31

Operating Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Mixed-Mode Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Running the AD73322L with ADCs

or DACs in Power-Down . . . . . . . . . . . . . . . . . . . . . . . 32

APPENDIX A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

DAC Timing Control Example . . . . . . . . . . . . . . . . . . . . . 34

APPENDIX B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Configuring an AD73322L to Operate in Data Mode . . 35

APPENDIX C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Configuring an AD73322L to Operate in Mixed Mode . . . 37

OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . 40

REV. 0

–39–

AD73322L

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

28-Lead Wide Body SOIC

(R-28)

0.7125 (18.10)

0.6969 (17.70)

28

15

14

1

PIN 1

0.1043 (2.65)

0.0926 (2.35)

0.0291 (0.74)

0.0098 (0.25)

ꢃ 45ꢁ

0.0500 (1.27)

0.0157 (0.40)

8ꢁ

0ꢁ

0.0500

(1.27)

BSC

0.0192 (0.49)

0.0138 (0.35)

0.0118 (0.30)

0.0040 (0.10)

SEATING

PLANE

0.0125 (0.32)

0.0091 (0.23)

28-Lead Thin Shrink SO (TSSOP)

(RU-28)

0.386 (9.80)

0.378 (9.60)

28

15

0.177 (4.50)

0.169 (4.30)

0.256 (6.50)

0.246 (6.25)

14

1

PIN 1

0.006 (0.15)

0.002 (0.05)

0.0433 (1.10)

MAX

8ꢁ

0ꢁ

0.0256 (0.65) 0.0118 (0.30)

0.028 (0.70)

0.020 (0.50)

SEATING

PLANE

0.0079 (0.20)

0.0035 (0.090)

BSC

0.0075 (0.19)

44-Lead Plastic Thin Quad Flatpack (LQFP)

(ST-44A)

0.640 (16.25)

0.620 (15.75)

SQ

0.063 (1.60)

MAX

0.553 (14.05)

0.549 (13.95)

SQ

0.030 (0.75)

0.019 (0.50)

44

34

1

33

SEATING

PLANE

0.397 (10.07)

0.391 (9.93)

TOP VIEW

SQ

(PINS DOWN)

0.004 (0.10)

MAX

23

11

22

12

0.006 (0.15)

0.002 (0.05)

0.042 (1.07)

0.037 (0.93)

0.016 (0.40)

0.012 (0.30)

0.057 (1.45)

0.053 (1.35)

–40–

REV. 0


型号：	EVAL-AD73322LEB
厂家：	ADI
描述：	Low Cost, Low Power CMOS General-Purpose Dual Analog Front End 低成本，低功耗CMOS通用双通道模拟前端
文件：	总40页 (文件大小：432K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

EVAL-AD73322LEB [ADI]

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