EVAL-ADF7020DBZ2 [ADI]
High Performance, ISM Band, FSK/ASK Transceiver IC; 高性能， ISM频段FSK / ASK收发器IC
| 型号： | EVAL-ADF7020DBZ2 |
| 厂家： | 
ADI |
| 描述： | High Performance, ISM Band, FSK/ASK Transceiver IC |
| 文件： | 总48页 (文件大小：719K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
High Performance, ISM Band,
FSK/ASK Transceiver IC
ADF7020
On-chip VCO and fractional-N PLL
On-chip 7-bit ADC and temperature sensor
Fully automatic frequency control loop (AFC) compensates
for 25 ppm crystal at 862 MHz to 956 MHz or 50 ppm at
431 MHz to 478 MHz
Data Sheet
FEATURES
Low power, low IF transceiver
Frequency bands
431 MHz to 478 MHz
862 MHz to 956 MHz
Data rates supported
0.15 kbps to 200 kbps, FSK
0.15 kbps to 64 kbps, ASK
2.3 V to 3.6 V power supply
Programmable output power
−16 dBm to +13 dBm in 0.3 dBm steps
Receiver sensitivity
−119 dBm at 1 kbps, FSK
−112 dBm at 9.6 kbps, FSK
−106.5 dBm at 9.6 kbps, ASK
Low power consumption
19 mA in receive mode
Digital RSSI
Integrated Tx/Rx switch
Leakage current of <1 µA in power-down mode
APPLICATIONS
Low cost wireless data transfer
Remote control/security systems
Wireless metering
Keyless entry
Home automation
Process and building control
Wireless voice
26.8 mA in transmit mode (10 dBm output)
−3 dBm IIP3 in high linearity mode
FUNCTIONAL BLOCK DIAGRAM
RSET
CREG[1:4]
LDO(1:4)
ADCIN
MUXOUT
ADF7020
TEMP
R
TEST MUX
LNA
OFFSET
SENSOR
CORRECTION
LNA
FSK/ASK
DEMODULATOR
DATA
SYNCHRONIZER
RFIN
MUX
7-BIT ADC
RSSI
IF FILTER
RFINB
GAIN
OFFSET
CORRECTION
CE
AGC
CONTROL
DATA CLK
DATA I/O
Tx/Rx
CONTROL
FSK MOD
CONTROL
GAUSSIAN
FILTER
Σ-Δ
MODULATOR
AFC
CONTROL
INT/LOCK
DIVIDERS/
MUXING
DIV P
N/N + 1
RFOUT
SLE
SDATA
SREAD
SCLK
SERIAL
PORT
VCO
CP
PFD
CLK
DIV
DIV R
OSC
VCOIN CPOUT
CLKOUT
OSC1 OSC2
Figure 1.
Rev. D
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rightsof third parties that may result fromits use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks andregisteredtrademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2005–2012 Analog Devices, Inc. All rights reserved.
ADF7020
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Image Rejection Calibration..................................................... 26
Transmit Protocol and Coding Considerations ..................... 27
Device Programming after Initial Power-Up ......................... 27
Interfacing to Microcontroller/DSP ........................................ 27
Power Consumption and battery lifetime calculations......... 28
Serial Interface ................................................................................ 31
Readback Format........................................................................ 31
Registers........................................................................................... 32
Register 0—N Register............................................................... 32
Register 1—Oscillator/Filter Register...................................... 33
Applications....................................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 3
General Description ......................................................................... 4
Specifications..................................................................................... 5
Timing Characteristics..................................................................... 8
Timing Diagrams.......................................................................... 8
Absolute Maximum Ratings.......................................................... 10
ESD Caution................................................................................ 10
Pin Configuration and Function Descriptions........................... 11
Typical Performance Characteristics ........................................... 13
Frequency Synthesizer ................................................................... 15
Reference Input........................................................................... 15
Choosing Channels for Best System Performance................. 17
Transmitter ...................................................................................... 18
RF Output Stage.......................................................................... 18
Modulation Schemes.................................................................. 18
Receiver............................................................................................ 20
RF Front End............................................................................... 20
RSSI/AGC.................................................................................... 21
FSK Demodulators on the ADF7020....................................... 21
FSK Correlator/Demodulator................................................... 21
Linear FSK Demodulator .......................................................... 23
AFC .............................................................................................. 23
Automatic Sync Word Recognition ......................................... 24
Applications Information .............................................................. 25
LNA/PA Matching...................................................................... 25
Register 2—Transmit Modulation Register (ASK/OOK
Mode)........................................................................................... 34
Register 2—Transmit Modulation Register (FSK Mode) ..... 35
Register 2—Transmit Modulation Register (GFSK/GOOK
Mode)........................................................................................... 36
Register 3—Receiver Clock Register ....................................... 37
Register 4—Demodulator Setup Register ............................... 38
Register 5—Sync Byte Register................................................. 39
Register 6—Correlator/Demodulator Register ...................... 40
Register 7—Readback Setup Register...................................... 41
Register 8—Power-Down Test Register .................................. 42
Register 9—AGC Register......................................................... 43
Register 10—AGC 2 Register.................................................... 44
Register 11—AFC Register ....................................................... 44
Register 12—Test Register......................................................... 45
Register 13—Offset Removal and Signal Gain Register ....... 46
Outline Dimensions....................................................................... 47
Ordering Guide .......................................................................... 47
Rev. D | Page 2 of 48
Data Sheet
ADF7020
REVISION HISTORY
8/12—Rev. C to Rev. D
Changes to Figure 24 ......................................................................17
Changes to the Setting Up the ADF7020 for GFSK Section .....19
Changes to Table 6 ..........................................................................21
Changes to Table 9 ..........................................................................23
Changes to External AFC Section.................................................23
Deleted Maximum AFC Range Section.......................................23
Added AFC Performance Section.................................................24
Changes to Internal Rx/Tx Switch Section..................................25
Changes to Figure 32 ......................................................................25
Changes to Transmit Protocol and Coding Considerations
Section ..............................................................................................26
Added Text Relating to Figure 37 .................................................27
Changes to Figure 41 ......................................................................31
Changes to Register 1—Oscillator/Filter Register
Comments........................................................................................31
Changes to Figure 42 ......................................................................32
Changes to Register 2—Transmit Modulation Register
(FSK Mode) Comments .................................................................33
Changes to Figure 44 ......................................................................34
Changes to Register 2—Transmit Modulation Register
Added EPAD Notation ...................................................................11
Changed CP-48-3 Package to CP-48-5 Package..........................47
Updated Outline Dimensions........................................................47
Changes to Ordering Guide...........................................................47
5/11—Rev. B to Rev. C
Added Exposed Pad Notation to Outline Dimensions ..............47
Changes to Ordering Guide...........................................................47
8/07—Rev. A to Rev. B
Changes to Features ..........................................................................1
Changes to General Description .....................................................4
Changes to Table 1 ............................................................................5
Changes to Table 2 ............................................................................8
Changes to Reference Input Section.............................................15
Changes to N Counter Section......................................................16
Changes to Choosing Channels for Best Performance Section 17
Changes to Table 5 ..........................................................................20
Changes to FSK Correlator Register Settings Section ................22
Added Image Rejection Calibration Section ...............................26
Added Figure 41 ..............................................................................30
Changes to Readback Format Section..........................................31
Changes to Register 9—AGC Register Comments Section.......43
Added Register 12—Test Register Comments Section ..............45
(GFSK/GOOK Mode) Comments................................................34
Changes to Register 4—Demodulator Setup Register
Comments........................................................................................36
Changes to Figure 51 ......................................................................41
Changes to Figure 53 ......................................................................42
Changes to Ordering Guide...........................................................45
4/06—Rev. 0 to Rev. A
Changes to Features ..........................................................................1
Changes to Table 1 ............................................................................5
6/05—Revision 0: Initial Version
Rev. D | Page 3 of 48
ADF7020
Data Sheet
GENERAL DESCRIPTION
The ADF7020 is a low power, highly integrated FSK/ASK/OOK
transceiver designed for operation in the license-free ISM bands
at 433 MHz, 868 MHz, and 915 MHz, as well as the proposed
Japanese RFID band at 950 MHz. A Gaussian data filter option
is available to allow either GFSK or G-ASK modulation, which
provides a more spectrally efficient modulation. In addition to
these modulation options, the ADF7020 can also be used to
perform both MSK and GMSK modulation, where MSK is a
special case of FSK with a modulation index of 0.5. The modula-
tion index is calculated as twice the deviation divided by the
data rate. MSK is spectrally equivalent to O-QPSK modulation
with half-sinusoidal Tx baseband shaping, so the ADF7020 can
also support this modulation option by setting up the device in
MSK mode.
The transmitter output power is programmable in 0.3 dB steps
from −16 dBm to +13 dBm. The transceiver RF frequency,
channel spacing, and modulation are programmable using a
simple 3-wire interface. The device operates with a power
supply range of 2.3 V to 3.6 V and can be powered down when
not in use.
A low IF architecture is used in the receiver (200 kHz),
minimizing power consumption and the external component
count and avoiding interference problems at low frequencies.
The ADF7020 supports a wide variety of programmable
features, including Rx linearity, sensitivity, and IF bandwidth,
allowing the user to trade off receiver sensitivity and selectivity
against current consumption, depending on the application.
The receiver also features a patent-pending automatic frequency
control (AFC) loop, allowing the PLL to track out the frequency
error in the incoming signal.
This device is suitable for circuit applications that meet the
European ETSI-300-220, the North American FCC (Part 15),
or the Chinese Short Range Device regulatory standards. A
complete transceiver can be built using a small number of
external discrete components, making the ADF7020 very
suitable for price-sensitive and area-sensitive applications.
An on-chip ADC provides readback of an integrated tempera-
ture sensor, an external analog input, the battery voltage, or the
RSSI signal, which provides savings on an ADC in some appli-
cations. The temperature sensor is accurate to 10°C over the
full operating temperature range of −40°C to +85°C. This
accuracy can be improved by doing a 1-point calibration at
room temperature and storing the result in memory.
The transmitter block on the ADF7020 contains a VCO and
low noise fractional-N PLL with an output resolution of
<1 ppm. This frequency agile PLL allows the ADF7020 to be
used in frequency-hopping spread spectrum (FHSS) systems.
The VCO operates at twice the fundamental frequency to
reduce spurious emissions and frequency-pulling problems.
Rev. D | Page 4 of 48
Data Sheet
ADF7020
SPECIFICATIONS
VDD = 2.3 V to 3.6 V, GND = 0 V, TA = TMIN to TMAX, unless otherwise noted. Typical specifications are at VDD = 3 V, TA = 25°C.
All measurements are performed using the EVAL-ADF7020DBZx using the PN9 data sequence, unless otherwise noted.
Table 1.
Parameter
Min
Typ
Max
Unit
Test Conditions
RF CHARACTERISTICS
Frequency Ranges (Direct Output)
862
902
928
431
440
RF/256
870
928
956
440
478
24
MHz
MHz
MHz
MHz
MHz
MHz
VCO adjust = 0, VCO bias = 10
VCO adjust = 3, VCO bias = 10
VCO adjust = 3, VCO bias = 12, VDD = 2.7 V to 3.6 V
VCO adjust = 0, VCO bias = 10
VCO adjust = 3, VCO bias = 12
Frequency Ranges (Divide-by-2 Mode)
Phase Frequency Detector Frequency
TRANSMISSION PARAMETERS
Data Rate
FSK/GFSK
OOK/ASK
OOK/ASK
0.15
0.15
0.3
200
641
100
kbps
kbps
kbaud
Using Manchester encoding
Frequency Shift Keying
GFSK/FSK Frequency Deviation2, 3
1
4.88
100
110
620
kHz
kHz
Hz
PFD = 3.625 MHz
PFD = 20 MHz
PFD = 3.625 MHz
Deviation Frequency Resolution
Gaussian Filter BT
0.5
Amplitude Shift Keying
ASK Modulation Depth
PA Off Feedthrough in OOK Mode
Transmit Power4
Transmit Power Variation vs.
Temperature
30
dB
−50
1
dBm
dBm
dB
−20
+13
VDD = 3.0 V, TA = 25°C
From −40°C to +85°C
Transmit Power Variation vs. VDD
Transmit Power Flatness
Programmable Step Size
−20 dBm to +13 dBm
Integer Boundary
1
1
dB
dB
From 2.3 V to 3.6 V at 915 MHz, TA = 25°C
From 902 MHz to 928 MHz, 3 V, TA = 25°C
0.3125
−55
−65
dB
dBc
dBc
50 kHz loop BW
Reference
Harmonics
Second Harmonic
Third Harmonic
All Other Harmonics
VCO Frequency Pulling, OOK Mode
Optimum PA Load Impedance5
−27
−21
−35
30
39 + j61
48 + j54
54 + j94
dBc
dBc
dBc
kHz rms
Ω
Unfiltered conductive
DR = 9.6 kbps
FRF = 915 MHz
FRF = 868 MHz
FRF = 433 MHz
Ω
Ω
RECEIVER PARAMETERS
FSK/GFSK Input Sensitivity
At BER = 1E − 3, FRF = 915 MHz,
LNA and PA matched separately6
Sensitivity at 1 kbps
Sensitivity at 9.6 kbps
Sensitivity at 200 kbps
OOK Input Sensitivity
Sensitivity at 1 kbps
Sensitivity at 9.6 kbps
−119.2
−112.8
−100
dBm
dBm
dBm
FDEV = 5 kHz, high sensitivity mode7
FDEV = 10 kHz, high sensitivity mode
FDEV = 50 kHz, high sensitivity mode
At BER = 1E − 3, FRF = 915 MHz
High sensitivity mode
−116
−106.5
dBm
dBm
High sensitivity mode
Rev. D | Page 5 of 48
ADF7020
Data Sheet
Parameter
Min
Typ
Max
Unit
Test Conditions
LNA and Mixer, Input IP37
Enhanced Linearity Mode
Low Current Mode
High Sensitivity Mode
Rx Spurious Emissions8
−3
−5
−24
dBm
dBm
dBm
dBm
dBm
Pin = −20 dBm, 2 CW interferers
FRF = 915 MHz, F1 = FRF + 3 MHz
F2 = FRF + 6 MHz, maximum gain
<1 GHz at antenna input
−57
−47
>1 GHz at antenna input
AFC
Pull-In Range at 868 MHz/915 MHz
Pull-In Range at 433 MHz
Response Time
50
25
48
1
kHz
kHz
Bits
kHz
IF_BW = 200 kHz
IF_BW = 200 kHz
Modulation index = 0.875
Accuracy
CHANNEL FILTERING
Desired signal 3 dB above the input sensitivity level,
CW interferer power level increased until BER = 10−3,
image channel excluded
Adjacent Channel Rejection
(Offset = 1 × IF Filter BW Setting)
Second Adjacent Channel Rejection
(Offset = 2 × IF Filter BW Setting)
Third Adjacent Channel Rejection
(Offset = 3 × IF Filter BW Setting)
27
50
55
30
dB
dB
dB
dB
IF filter BW settings = 100 kHz, 150 kHz, 200 kHz
IF filter BW settings = 100 kHz, 150 kHz, 200 kHz
IF filter BW settings = 100 kHz, 150 kHz, 200 kHz
Image at FRF = 400 kHz
Image Channel Rejection
(Uncalibrated)
Image Channel Rejection (Calibrated)
CO-CHANNEL REJECTION
Wideband Interference Rejection
50
−2
70
dB
dB
dB
Image at FRF = 400 kHz
Swept from 100 MHz to 2 GHz, measured as channel
rejection
BLOCKING
Desired signal 3 dB above the input sensitivity level,
CW interferer power level increased until BER = 10−2
1 MHz
5 MHz
10 MHz
60
68
65
72
dB
dB
dB
dB
dBm
Ω
10 MHz (High Linearity Mode)
Saturation (Maximum Input Level)
LNA Input Impedance
12
FSK mode, BER = 10−3
FRF = 915 MHz, RFIN to GND
FRF = 868 MHz
24 − j60
26 − j63
71 − j128
Ω
Ω
FRF = 433 MHz
RSSI
Range at Input
−110 to
−24
dBm
Linearity
2
3
150
dB
dB
µs
Absolute Accuracy
Response Time
PHASE-LOCKED LOOP
VCO Gain
See the RSSI/AGC section
65
MHz/V
902 MHz to 928 MHz band,
VCO adjust = 0, VCO_BIAS_SETTING = 10
130
65
−89
MHz/V
MHz/V
dBc/Hz
860 MHz to 870 MHz band, VCO adjust = 0
433 MHz, VCO adjust = 0
PA = 0 dBm, VDD = 3.0 V, PFD = 10 MHz,
FRF = 915 MHz, VCO_BIAS_SETTING = 10
Phase Noise (In-Band)
Phase Noise (Out-of-Band)
Residual FM
PLL Settling
−110
128
40
dBc/Hz
Hz
µs
1 MHz offset
From 200 Hz to 20 kHz, FRF = 868 MHz
Measured for a 10 MHz frequency step to within
5 ppm accuracy, PFD = 20 MHz, LBW = 50 kHz
Rev. D | Page 6 of 48
Data Sheet
ADF7020
Parameter
Min
Typ
Max
Unit
Test Conditions
REFERENCE INPUT
Crystal Reference
External Oscillator
Load Capacitance
Crystal Start-Up Time
3.625
3.625
24
24
MHz
MHz
pF
ms
33
2.1
1.0
See crystal manufacturer’s specification sheet
11.0592 MHz crystal, using 33 pF load capacitors
Using 16 pF load capacitors
ms
Input Level
CMOS levels
See the Reference Input section
ADC PARAMETERS
INL
DNL
1
1
LSB
LSB
From 2.3 V to 3.6 V, TA = 25°C
From 2.3 V to 3.6 V, TA = 25°C
TIMING INFORMATION
Chip Enabled to Regulator Ready
Chip Enabled to RSSI Ready
Tx to Rx Turnaround Time
10
3.0
µs
ms
CREG = 100 nF
See Table 11 for more details
Time to synchronized data out, includes AGC settling;
see the AGC Information and Timing section
150 µs +
(5 × TBIT)
LOGIC INPUTS
Input High Voltage, VINH
0.7 ×
VDD
V
V
Input Low Voltage, VINL
0.2 ×
VDD
Input Current, IINH/IINL
Input Capacitance, CIN
Control Clock Input
LOGIC OUTPUTS
1
10
50
µA
pF
MHz
Output High Voltage, VOH
DVDD −
0.4
V
IOH = 500 µA
IOL = 500 µA
Output Low Voltage, VOL
CLKOUT Rise/Fall
CLKOUT Load
0.4
5
10
+85
V
ns
pF
°C
TEMPERATURE RANGE, TA
POWER SUPPLIES
Voltage Supply
−40
2.3
VDD
3.6
V
All VDD pins must be tied together
Transmit Current Consumption
FRF = 915 MHz, VDD = 3.0 V,
PA is matched to 50 Ω
−20 dBm
−10 dBm
0 dBm
14.8
15.9
19.1
28.5
26.8
mA
mA
mA
mA
mA
Combined PA and LNA matching network as on
EVAL-ADF7020DBZx boards
VCO_BIAS_SETTING = 12
10 dBm
10 dBm
PA matched separately with external antenna
switch, VCO_BIAS_SETTING = 12
Receive Current Consumption
Low Current Mode
High Sensitivity Mode
Power-Down Mode
19
21
mA
mA
Low Power Sleep Mode
0.1
1
µA
1 Higher data rates are achievable, depending on local regulations.
2 For the definition of frequency deviation, see the Register 2—Transmit Modulation Register (FSK Mode) section.
3 For the definition of GFSK frequency deviation, see the Register 2—Transmit Modulation Register (GFSK/GOOK Mode) section.
4 Measured as maximum unmodulated power. Output power varies with both supply and temperature.
5 For matching details, see the LNA/PA Matching section and the AN-764 Application Note.
6 Sensitivity for combined matching network case is typically 2 dB less than separate matching networks.
7 See Table 5 for a description of different receiver modes.
8 Follow the matching and layout guidelines to achieve the relevant FCC/ETSI specifications.
Rev. D | Page 7 of 48
ADF7020
Data Sheet
TIMING CHARACTERISTICS
VDD = 3 V ꢀ10% VGND = 1 V% TA = 25°C% unless otherwise noted. Guaranteed by design% not production tested.
Table 2.
Parameter
Limit at TMIN to TMAX
Unit
ns
ns
ns
ns
ns
ns
ns
ns
Test Conditions/Comments
SDATA to SCLK setup time
SDATA to SCLK hold time
SCLK high duration
SCLK low duration
SCLK to SLE setup time
t1
t2
t3
t4
t5
t6
t8
t9
t10
>10
>10
>25
>25
>10
>20
<25
<25
>10
SLE pulse width
SCLK to SREAD data valid, readback
SREAD hold time after SCLK, readback
SCLK to SLE disable time, readback
ns
TIMING DIAGRAMS
t3
t4
SCLK
t1
t2
DB1
DB0 (LSB)
SDATA
SLE
DB31 (MSB)
DB30
DB2
(CONTROL BIT C2)
(CONTROL BIT C1)
t6
t5
Figure 2. Serial Interface Timing Diagram
t1
t2
SCLK
SDATA
SLE
R7_DB0
(CONTROL BIT C1)
t3
t10
X
RV16
RV15
RV2
RV1
SREAD
t9
t8
Figure 3. Readback Timing Diagram
Rev. D | Page 8 of 48
Data Sheet
ADF7020
±1 × DATA RATE/32
1/DATA RATE
RxCLK
RxDATA
DATA
Figure 4. RxData/RxCLK Timing Diagram
1/DATA RATE
TxCLK
TxDATA
DATA
FETCH
SAMPLE
NOTES
1. TxCLK ONLY AVAILABLE IN GFSK MODE.
Figure 5. TxData/TxCLK Timing Diagram
Rev. D | Page 9 of 48
ADF7020
Data Sheet
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
Table 3.
Parameter
VDD to GND1
Rating
−0.3 V to +5 V
Analog I/O Voltage to GND
Digital I/O Voltage to GND
Operating Temperature Range
Industrial (B Version)
Storage Temperature Range
Maximum Junction Temperature
MLF θJA Thermal Impedance
Reflow Soldering
−0.3 V to AVDD + 0.3 V
−0.3 V to DVDD + 0.3 V
This device is a high performance RF integrated circuit with an
ESD rating of <2 kV, and is ESD sensitive. Proper precautions
should be taken for handling and assembly.
−40°C to +85°C
−65°C to +125°C
150°C
26°C/W
ESD CAUTION
Peak Temperature
Time at Peak Temperature
260°C
40 sec
1 GND = GND1 = RFGND = GND4 = VCO GND = 0 V.
Rev. D | Page 10 of 48
Data Sheet
ADF7020
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
CLKOUT
DATA CLK
DATA I/O
INT/LOCK
VDD2
CREG2
ADCIN
GND2
VCOIN
CREG1
VDD1
RFOUT
RFGND
RFIN
1
2
3
4
5
6
7
8
9
36
35
34
33
32
31
30
29
28
27
26
25
ADF7020
TOP VIEW
(Not to Scale)
RFINB
R
LNA
SCLK
VDD4
RSET
10
SREAD
SDATA
SLE
CREG4 11
12
GND4
NOTES
1. EXPOSED PAD MUST BE CONNECTED TO GROUND.
Figure 6. Pin Configuration
Table 4. Pin Function Descriptions
Pin No.
Mnemonic
Description
1
VCOIN
The tuning voltage on this pin determines the output frequency of the voltage-controlled oscillator (VCO).
The higher the tuning voltage, the higher the output frequency.
2
3
4
CREG1
VDD1
Regulator Voltage for PA Block. A 100 nF in parallel with a 5.1 pF capacitor should be placed between this
pin and ground for regulator stability and noise rejection.
Voltage Supply for PA Block. Decoupling capacitors of 0.1 μF and 10 pF should be placed as close as
possible to this pin. All VDD pins should be tied together.
The modulated signal is available at this pin. Output power levels are from −20 dBm to +13 dBm. The
output should be impedance matched to the desired load using suitable components. See the Transmitter
section.
RFOUT
5
6
RFGND
RFIN
Ground for Output Stage of Transmitter. All GND pins should be tied together.
LNA Input for Receiver Section. Input matching is required between the antenna and the differential LNA
input to ensure maximum power transfer. See the LNA/PA Matching section.
7
8
9
10
RFINB
RLNA
VDD4
RSET
Complementary LNA Input. See the LNA/PA Matching section.
External bias resistor for LNA. Optimum resistor is 1.1 kΩ with 5% tolerance.
Voltage Supply for LNA/MIXER Block. This pin should be decoupled to ground with a 10 nF capacitor.
External Resistor to Set Charge Pump Current and Some Internal Bias Currents. Use 3.6 kΩ with 5%
tolerance.
11
CREG4
Regulator Voltage for LNA/MIXER Block. A 100 nF capacitor should be placed between this pin and GND
for regulator stability and noise rejection.
12
GND4
Ground for LNA/MIXER Block.
13 to 18
MIX_I, MIX_I,
MIX_Q, MIX_Q,
FILT_I, FILT_I
Signal Chain Test Pins. These pins are high impedance under normal conditions and should be left
unconnected.
19, 22
GND4
Ground for LNA/MIXER Block.
20, 21, 23
FILT_Q, FILT_Q,
TEST_A
CE
Signal Chain Test Pins. These pins are high impedance under normal conditions and should be left
unconnected.
24
25
26
Chip Enable. Bringing CE low puts the ADF7020 into complete power-down. Register values are lost when
CE is low, and the part must be reprogrammed once CE is brought high.
Load Enable, CMOS Input. When LE goes high, the data stored in the shift registers is loaded into one of
the fourteen latches. A latch is selected using the control bits.
Serial Data Input. The serial data is loaded MSB first with the two LSBs as the control bits. This pin is a high
impedance CMOS input.
SLE
SDATA
Rev. D | Page 11 of 48
ADF7020
Data Sheet
Pin No.
Mnemonic
Description
27
SREAD
Serial Data Output. This pin is used to feed readback data from the ADF7020 to the microcontroller. The
SCLK input is used to clock each readback bit (AFC, ADC readback) from the SREAD pin.
28
SCLK
Serial Clock Input. This serial clock is used to clock in the serial data to the registers. The data is latched into
the 24-bit shift register on the CLK rising edge. This pin is a digital CMOS input.
29
30
GND2
ADCIN
Ground for Digital Section.
Analog-to-Digital Converter Input. The internal 7-bit ADC can be accessed through this pin. Full scale is 0 V
to 1.9 V. Readback is made using the SREAD pin.
31
32
33
CREG2
Regulator Voltage for Digital Block. A 100 nF in parallel with a 5.1 pF capacitor should be placed between
this pin and ground for regulator stability and noise rejection.
Voltage Supply for Digital Block. A decoupling capacitor of 10 nF should be placed as close as possible to
this pin.
Bidirectional Pin. In output mode (interrupt mode), the ADF7020 asserts the INT/ LOCK pin when it has
found a match for the preamble sequence. In input mode (lock mode), the microcontroller can be used to
lock the demodulator threshold when a valid preamble has been detected. Once the threshold is locked,
NRZ data can be reliably received. In this mode, a demodulation lock can be asserted with minimum delay.
VDD2
INT/LOCK
34
35
DATA I/O
DATA CLK
Transmit Data Input/Received Data Output. This is a digital pin, and normal CMOS levels apply.
In receive mode, the pin outputs the synchronized data clock. The positive clock edge is matched to the
center of the received data. In GFSK transmit mode, the pin outputs an accurate clock to latch the data
from the microcontroller into the transmit section at the exact required data rate. See the Gaussian
Frequency Shift Keying (GFSK) section.
36
37
38
CLKOUT
MUXOUT
OSC2
A Divided-Down Version of the Crystal Reference with Output Driver. The digital clock output can be
used to drive several other CMOS inputs, such as a microcontroller clock. The output has a 50:50 mark-
space ratio.
This pin provides the Lock_Detect signal, which is used to determine if the PLL is locked to the correct
frequency. Other signals include Regulator_Ready, which is an indicator of the status of the serial interface
regulator.
The reference crystal should be connected between this pin and OSC1. A TCXO reference can be used by
driving this pin with CMOS levels and disabling the crystal oscillator.
39
40
OSC1
VDD3
The reference crystal should be connected between this pin and OSC2.
Voltage Supply for the Charge Pump and PLL Dividers. This pin should be decoupled to ground with a
0.01 µF capacitor.
41
42
CREG3
CPOUT
VDD
Regulator Voltage for Charge Pump and PLL Dividers. A 100 nF in parallel with a 5.1 pF capacitor should be
placed between this pin and ground for regulator stability and noise rejection.
Charge Pump Output. This output generates current pulses that are integrated in the loop filter. The
integrated current changes the control voltage on the input to the VCO.
Voltage Supply for VCO Tank Circuit. This pin should be decoupled to ground with a 0.01 µF capacitor.
Grounds for VCO Block.
43
44 to 47
GND, GND1,
VCO GND
48
CVCO
EP
A 22 nF capacitor should be placed between this pin and CREG1 to reduce VCO noise.
Exposed Pad. The exposed pad must be connected to ground.
Rev. D | Page 12 of 48
Data Sheet
ADF7020
TYPICAL PERFORMANCE CHARACTERISTICS
CARRIER POWER –0.28dBm ATTEN 0.00dB MKR1
REF –70.00dBc/Hz
10.0000kHz
–87.80dBc/Hz
MKR4 3.482GHz
SWEEP 16.52ms (601pts)
REF 10dBm
PEAK
log
ATTEN 20dB
10.00
dB/DIV
1
1
10dB/DIV
3
4
REF LEVEL
10.00dBm
1kHz
FREQUENCY OFFSET
10MHz
START 100MHz
RES BW 3MHz
STOP 10.000GHz
SWEEP 16.52ms (601pts)
VBW 3MHz
Figure 7. Phase Noise Response at 868.3 MHz, VDD = 3.0 V, ICP = 1.5 mA
Figure 10. Harmonic Response, RFOUT Matched to 50 Ω, No Filter
Δ Mkr1 1.834GHz
REF 15dBm
1R
ATTEN 30dB
–62.57dB
10
NORM
log
PRBS PN9
DR = 7.1kbps
10dB/DIV
FDEV = 4.88kHz
RBW = 300kHz
20
30
MARKER
Δ
1.834000000GHz
–62.57dB
FSK
40
LgAv
W1 S2
S3 FC
AA
1
50
£(f):
FTun
Swp
60
GFSK
70
913.28
913.30
913.32
913.36
913.38
START 800MHz
#RES BW 30kHz
STOP 5.000GHz
SWEEP 5.627s (601pts)
FREQUENCY (MHz)
VBW 30kHz
Figure 8. Output Spectrum in FSK and GFSK Modulation
Figure 11. Harmonic Response, Murata Dielectric Filter
0
–5
10
0
200kHz FILTER BW
–10
–15
–20
–25
–30
–35
–40
–45
–50
–55
–60
–65
–70
–10
–20
–30
–40
–50
ASK
OOK
150kHz FILTER BW
100kHz FILTER BW
GOOK
–400 –300 –200 –100
–350 –250 –150 –50
0
100 200 300 400 500 600
150 250 350 450 550
899.60
899.80
900.00
900.20
900.40
900.60
900.80
50
FREQUENCY (MHz)
IF FREQ (kHz)
Figure 9. IF Filter Response
Figure 12. Output Spectrum in ASK, OOK, and GOOK Modes, DR = 10 kbps
Rev. D | Page 13 of 48
ADF7020
Data Sheet
20
0
–1
–2
–3
–4
–5
–6
–7
–8
DATA RATE = 1kbps FSK
IF BW = 100kHz
DEMOD BW = 0.77kHz
3.0V, +25°C
9µA
15
11µA
10
5
5µA
2.4V, +85°C
0
7µA
–5
3.6V, –40°C
–10
–15
–20
–25
1
5
9
13 17 21 25 29 33 37 41 45 49 53 57 61
PA SETTING
RF INPUT LEVEL (dBm)
Figure 13. PA Output Power vs. Setting
Figure 16. BER vs. VDD and Temperature
80
70
60
50
40
30
20
10
0
0
–1
–2
–3
–4
–5
–6
–7
–8
200.8k
DATA RATE
1.002k
DATA RATE
9.760k
DATA RATE
–10
FREQUENCY OF INTERFERER (MHz)
RF INPUT LEVEL (dBm)
Figure 14. Wideband Interference Rejection; Wanted Signal (880 MHz)
at 3 dB above Sensitivity Point
Figure 17. BER vs. Data Rate (Combined Matching Network)
Separate LNA and PA Matching Paths Typically
Improve Performance by 2 dB
Interferer = FM Jammer (9.76 kbps, 10 kHz Deviation)
–60
20
–65
–70
0
ACTUAL INPUT LEVEL
LINEAR AFC OFF
–75
–20
–80
–40
–85
CORRELATOR
AFC ON
RSSI READBACK LEVEL
–90
–60
–80
–95
CORRELATOR
AFC OFF
LINEAR AFC ON
–100
–105
–110
–100
–120
–120
–100
–80
–60
–40
–20
0
20
RF INPUT (dB)
FREQUENCY ERROR (kHz)
Figure 15. Digital RSSI Readback Linearity
Figure 18. Sensitivity vs. Frequency Error with AFC On/Off
Rev. D | Page 14 of 48
Data Sheet
ADF7020
FREQUENCY SYNTHESIZER
REFERENCE INPUT
R Counter
The 3-bit R counter divides the reference input frequency by an
integer ranging from 1 to 7. The divided-down signal is
presented as the reference clock to the phase frequency detector
(PFD). The divide ratio is set in Register 1. Maximizing the
PFD frequency reduces the N value. Every doubling of the PFD
gives a 3 dB benefit in phase noise, as well as reducing
occurrences of spurious components. The R register defaults to
R = 1 on power-up.
The on-board crystal oscillator circuitry (see Figure 19) can use
an inexpensive quartz crystal as the PLL reference. The oscilla-
tor circuit is enabled by setting R1_DB12 high. It is enabled by
default on power-up and is disabled by bringing CE low. Errors
in the crystal can be corrected using the automatic frequency
control (see the AFC section) feature or by adjusting the
fractional-N value (see the N Counter section). A single-ended
reference (TCXO, CXO) can also be used. The CMOS levels
should be applied to OSC2 with R1_DB12 set low.
PFD [Hz] = XTAL/R
MUXOUT and Lock Detect
The MUXOUT pin allows the user to access various digital
points in the ADF7020. The state of MUXOUT is controlled by
Bits R0_DB[29:31].
OSC1
OSC2
CP1
CP2
Regulator Ready
Figure 19. Oscillator Circuit on the ADF7020
Regulator ready is the default setting on MUXOUT after the
transceiver has been powered up. The power-up time of the
regulator is typically 50 µs. Because the serial interface is
powered from the regulator, the regulator must be at its
nominal voltage before the ADF7020 can be programmed. The
status of the regulator can be monitored at MUXOUT. When
the regulator ready signal on MUXOUT is high, programming
of the ADF7020 can begin.
Two parallel resonant capacitors are required for oscillation at
the correct frequency; their values are dependent on the crystal
specification. They should be chosen so that the series value of
capacitance added to the PCB track capacitance adds up to the
load capacitance of the crystal, usually 20 pF. PCB track
capacitance values might vary from 2 pF to 5 pF, depending on
board layout. Thus, CP1 and CP2 can be calculated using:
DV
DD
1
CL =
+ CPCB
1
1
+
CP1 CP2
REGULATOR READY
DIGITAL LOCK DETECT
ANALOG LOCK DETECT
R COUNTER OUTPUT
N COUNTER OUTPUT
PLL TEST MODES
Where possible, choose capacitors that have a low temperature
coefficient to ensure stable frequency operation over all
conditions.
MUX
CONTROL
MUXOUT
CLKOUT Divider and Buffer
The CLKOUT circuit takes the reference clock signal from the
oscillator section, shown in Figure 19, and supplies a divided-
down 50:50 mark-space signal to the CLKOUT pin. An even
divide from 2 to 30 is available. This divide number is set in
R1_DB[8:11]. On power-up, the CLKOUT defaults to
divide-by-8.
Σ-Δ TEST MODES
DGND
Figure 21. MUXOUT Circuit
Digital Lock Detect
DV
DD
CLKOUT
Digital lock detect is active high. The lock detect circuit is
located at the PFD. When the phase error on five consecutive
cycles is less than 15 ns, lock detect is set high. Lock detect
remains high until 25 ns phase error is detected at the PFD.
Because no external components are needed for digital lock
detect, it is more widely used than analog lock detect.
ENABLE BIT
DIVIDER
1 TO 15
OSC1
÷2
CLKOUT
Figure 20. CLKOUT Stage
Analog Lock Detect
To disable CLKOUT, set the divide number to 0. The output
buffer can drive up to a 20 pF load with a 10% rise time at
4.8 MHz. Faster edges can result in some spurious feedthrough
to the output. A small series resistor (50 Ω) can be used to slow
This N-channel open-drain lock detect should be operated with
an external pull-up resistor of 10 kΩ nominal. When a lock has
been detected, this output is high with narrow low going pulses.
the clock edges to reduce these spurs at fCLK
.
Rev. D | Page 15 of 48
ADF7020
Data Sheet
Voltage Regulators
N Counter
The ADF7020 contains four regulators to supply stable voltages
to the part. The nominal regulator voltage is 2.3 V. Each
regulator should have a 100 nF capacitor connected between
CREGx and GND. When CE is high, the regulators and other
associated circuitry are powered on, drawing a total supply
current of 2 mA. Bringing the chip-enable pin low disables the
regulators, reduces the supply current to less than 1 μA, and
erases all values held in the registers. The serial interface
operates off a regulator supply; therefore, to write to the part,
the user must have CE high and the regulator voltage must be
stabilized. Regulator status (CREG4) can be monitored using
the regulator ready signal from MUXOUT.
The feedback divider in the ADF7020 PLL consists of an 8-bit
integer counter and a 15-bit Σ-Δ fractional-N divider. The
integer counter is the standard pulse-swallow type common in
PLLs. This sets the minimum integer divide value to 31. The
fractional divide value gives very fine resolution at the output,
where the output frequency of the PLL is calculated as
Fractional_ N
fOUT PFD Integer _ N
215
REFERENCE IN
PFD/
4÷R
CHARGE
PUMP
VCO
4÷N
Loop Filter
The loop filter integrates the current pulses from the charge
pump to form a voltage that tunes the output of the VCO to the
desired frequency. It also attenuates spurious levels generated by
the PLL. A typical loop filter design is shown in Figure 22.
THIRD-ORDER
Σ-∆ MODULATOR
FRACTIONAL-N
INTEGER-N
Figure 23. Fractional-N PLL
CHARGE
VCO
PUMP OUT
The maximum N divide value is the combination of the
Integer_N (maximum = 255) and the Fractional_N (maximum
= 32767/32768) and puts a lower limit on the minimum
usable PFD.
Figure 22. Typical Loop Filter Configuration
In FSK, the loop should be designed so that the loop bandwidth
(LBW) is approximately one and a half times the data rate.
Widening the LBW excessively reduces the time spent jumping
between frequencies, but it can cause insufficient spurious
attenuation.
PFDMIN [Hz] = Maximum Required Output Frequency/(255 + 1)
For example, when operating in the European 868 MHz to
870 MHz band, PFDMIN equals 3.4 MHz. In the majority of
cases, it is advisable to use as high a value of PFD as possible
to obtain best phase noise performance.
For ASK systems, a wider LBW is recommended. The sudden
large transition between two power levels can result in VCO
pulling and can cause a wider output spectrum than is desired.
By widening the LBW to more than 10 times the data rate, the
amount of VCO pulling is reduced, because the loop settles
quickly back to the correct frequency. The wider LBW can
restrict the output power and data rate of ASK-based systems
compared with FSK-based systems.
Voltage Controlled Oscillator (VCO)
To minimize spurious emissions, the on-chip VCO operates
from 1724 MHz to 1912 MHz. The VCO signal is then divided
by 2 to give the required frequency for the transmitter and the
required LO frequency for the receiver.
The VCO should be recentered, depending on the required
frequency of operation, by programming the VCO Adjust Bits
R1_DB[20:21].
Narrow-loop bandwidths can result in the loop taking long
periods of time to attain lock. Careful design of the loop filter is
critical to obtaining accurate FSK/GFSK modulation.
The VCO is enabled as part of the PLL by the PLL Enable bit,
R0_DB28.
A further frequency divide-by-2 block is included to allow
operation in the lower 433 MHz and 460 MHz bands. To enable
operation in these bands, R1_DB13 should be set to 1. The
VCO needs an external 22 nF between the VCO and the
regulator to reduce internal noise.
For GFSK, it is recommended that an LBW of 1.0 to 1.5 times
the data rate be used to ensure that sufficient samples are
taken of the input data while filtering system noise. The free
design tool ADI SRD Design Studio™ can be used to design loop
filters for the ADF7020. It can also be used to view the effect of
loop filter bandwidth on the spectrum of the transmitted signal
for different combinations of modulation type, data rates, and
modulation indices.
Rev. D | Page 16 of 48
Data Sheet
ADF7020
VCO Bias Current
CHOOSING CHANNELS FOR BEST SYSTEM
PERFORMANCE
VCO bias current can be adjusted using Bit R1_DB19 to
Bit R1_DB16. To ensure VCO oscillation, the minimum bias
current setting under all conditions is 0xA.
The fractional-N PLL allows the selection of any channel within
868 MHz to 956 MHz (and 433 MHz using divide-by-2) to a
resolution of <300 Hz. This also facilitates frequency-hopping
systems.
VCO BIAS
TO N
R1_DB[16:19]
DIVIDER
Careful selection of the XTAL frequency is important to achieve
best spurious and blocking performance. The architecture of
fractional-N causes some level of the nearest integer channel to
couple directly to the RF output. This phenomenon is often
referred to as integer boundary spurious. If the desired RF channel
and the nearest integer channel are separated by a frequency of
less than the PLL loop bandwidth (LBW), the integer boundary
spurs are not attenuated by the loop.
MUX
TO PA
LOOP FILTER
÷2
VCO
÷2
220µF
CVCO PIN
VCO SELECT BIT
Figure 24. Voltage-Controlled Oscillator (VCO)
Integer boundary spurs can be significantly reduced in ampli-
tude by choosing XTAL values that place the wanted RF
channel away from integer multiples of the PFD.
Rev. D | Page 17 of 48
ADF7020
Data Sheet
TRANSMITTER
The PA is equipped with overvoltage protection, which makes it
robust in severe mismatch conditions. Depending on the applica-
tion, one can design a matching network for the PA to exhibit
optimum efficiency at the desired radiated output power level
for a wide range of different antennas, such as loop or mono-
pole antennas. See the LNA/PA Matching section for details.
RF OUTPUT STAGE
The PA of the ADF7020 is based on a single-ended, controlled
current, open-drain amplifier that has been designed to deliver
up to 13 dBm into a 50 Ω load at a maximum frequency of
956 MHz.
The PA output current and, consequently, the output power are
programmable over a wide range. The PA configurations in
FSK/GFSK and ASK/OOK modulation modes are shown in
Figure 25 and Figure 26, respectively. In FSK/GFSK modulation
mode, the output power is independent of the state of the
DATA I/O pin. In ASK/OOK modulation mode, it is dependent
on the state of the DATA I/O pin and Bit R2_DB29, which
selects the polarity of the TxData input. For each transmission
mode, the output power can be adjusted as follows:
PA Bias Currents
Control Bits R2_DB[30:31] facilitate an adjustment of the PA
bias current to further extend the output power control range,
if necessary. If this feature is not required, the default value of
7 μA is recommended. The output stage is powered down by
resetting Bit R2_DB4. To reduce the level of undesired spurious
emissions, the PA can be muted during the PLL lock phase by
toggling this bit.
MODULATION SCHEMES
Frequency Shift Keying (FSK)
FSK/GFSK
The output power is set using Bits R2_DB[9:14].
ASK
Frequency shift keying is implemented by setting the N value
for the center frequency and then toggling this with the TxData
line. The deviation from the center frequency is set using
Bits R2_DB[15:23]. The deviation from the center frequency
in Hz is
The output power for the inactive state of the TxData input
is set by Bits R2_DB[15:20]. The output power for the
active state of the TxData input is set by Bits R2_DB[9:14].
OOK
The output power for the active state of the TxData input
is set by Bits R2_DB[9:14]. The PA is muted when the TxData
input is inactive.
PFD Modulation Number
FSKDEVIATION[Hz]
214
where Modulation Number is a number from 1 to 511
R2_DB[30:31]
2
(R2_DB[15:23]).
Select FSK using Bits R2_DB[6:8].
6
IDAC
R2_DB[9:14]
RFOUT
R2_DB4
R2_DB5
+
PFD/
CHARGE
PUMP
PA STAGE
4R
DIGITAL
VCO
÷N
LOCK DETECT
RFGND
FSK DEVIATION
FREQUENCY
FROM VCO
Figure 25. PA Configuration in FSK/GFSK Mode
–
fDEV
fDEV
THIRD-ORDER
Σ-∆ MODULATOR
+
DATA I/O
ASK/OOK MODE
R2_DB29
TxDATA
FRACTIONAL-N
INTEGER-N
R2_DB[30:31]
Figure 27. FSK Implementation
6
R2_DB[9:14]
6
IDAC
6
0
R2_DB[15:23]
RFOUT
RFGND
R2_DB4
R2_DB5
+
DIGITAL
LOCK DETECT
FROM VCO
Figure 26. PA Configuration in ASK/OOK Mode
Rev. D | Page 18 of 48
Data Sheet
ADF7020
Gaussian Frequency Shift Keying (GFSK)
Amplitude Shift Keying (ASK)
Gaussian frequency shift keying reduces the bandwidth occu-
pied by the transmitted spectrum by digitally prefiltering the
TxData. A TxCLK output line is provided from the ADF7020
for synchronization of TxData from the microcontroller.
The TxCLK line can be connected to the clock input of a shift
register that clocks data to the transmitter at the exact data rate.
Amplitude shift keying is implemented by switching the output
stage between two discrete power levels. This is accomplished
by toggling the DAC, which controls the output level between
two 6-bit values set up in Register 2. A 0 TxData bit sends
Bits R2_DB[15:20] to the DAC. A high TxData bit sends
Bits R2_DB[9:14] to the DAC. A maximum modulation depth
of 30 dB is possible.
Setting Up the ADF7020 for GFSK
On-Off Keying (OOK)
To set up the frequency deviation, set the PFD and the modula-
tion control bits.
On-off keying is implemented by switching the output stage to a
certain power level for a high TxData bit and switching the
output stage off for a zero. For OOK, the transmitted power for
a high input is programmed using Bits R2_DB[9:14].
PFD ×2m
GFSKDEVIATION[Hz] =
212
where m is GFSK_Mod_Control, set using R2_DB[24:26].
To set up the GFSK data rate,
Gaussian On-Off Keying (GOOK)
Gaussian on-off keying represents a prefiltered form of OOK
modulation. The usually sharp symbol transitions are replaced
with smooth Gaussian filtered transitions, the result being a
reduction in frequency pulling of the VCO. Frequency pulling
of the VCO in OOK mode can lead to a wider than desired
BW, especially if it is not possible to increase the loop filter
BW > 300 kHz. The GOOK sampling clock samples data at the
data rate (see the Setting Up the ADF7020 for GFSK section).
PFD
DR [bps] =
DIVIDER_ FACTOR× INDEX _COUNTER
The INDEX_COUNTER variable controls the number of inter-
mediate frequency steps between the low and high frequency.
It is usually possible to achieve a given data rate with various
combinations of DIVIDER_FACTOR and INDEX_COUNTER.
Choosing a higher INDEX_COUNTER can help in improving
the spectral performance.
Rev. D | Page 19 of 48
ADF7020
Data Sheet
RECEIVER
The LNA has two basic operating modes: high gain/low noise
mode and low gain/low power mode. To switch between these
two modes, use the LNA_Mode bit, R6_DB15. The mixer is also
configurable between a low current and an enhanced linearity
mode using the mixer_linearity bit, R6_DB18.
RF FRONT END
The ADF7020 is based on a fully integrated, low IF receiver
architecture. The low IF architecture facilitates a very low
external component count and does not suffer from power line-
induced interference problems.
Based on the specific sensitivity and linearity requirements
of the application, it is recommended to adjust control bits
LNA_Mode (R6_DB15) and Mixer_Linearity (R6_DB18), as
outlined in Table 5.
Figure 28 shows the structure of the receiver front end. The
many programming options allow users to trade off sensitivity,
linearity, and current consumption against each other in the
way best suitable for their applications. To achieve a high level
of resilience against spurious reception, the LNA features a
differential input. Switch SW2 shorts the LNA input when
transmit mode is selected (R0_DB27 = 0). This feature facili-
tates the design of a combined LNA/PA matching network,
avoiding the need for an external Rx/Tx switch. See the
LNA/PA Matching section for details on the design of the
matching network.
The gain of the LNA is configured by the LNA_Gain field,
R9_DB[20:21], and can be set by either the user or the
automatic gain control (AGC) logic.
IF Filter Settings/Calibration
Out-of-band interference is rejected by means of a fourth-order
Butterworth polyphase IF filter centered around a frequency of
200 kHz. The bandwidth of the IF filter can be programmed
between 100 kHz and 200 kHz by using Control Bits R1_DB[22:23]
and should be chosen as a compromise between interference rejec-
tion, attenuation of the desired signal, and the AFC pull-in range.
I (TO FILTER)
RFIN
Tx/Rx SELECT
SW2 LNA
LO
(R0_DB27)
RFINB
Q (TO FILTER)
To compensate for manufacturing tolerances, the IF filter
should be calibrated once after power-up. The IF filter calibra-
tion logic requires that the IF filter divider in Bits R6_DB[20:28]
be set as dependent on the crystal frequency. Once initiated
by setting Bit R6_DB19, the calibration is performed
automatically without any user intervention. The calibration
time is 200 μs, during which the ADF7020 should not be
accessed. It is important not to initiate the calibration cycle
before the crystal oscillator has fully settled. If the AGC loop is
disabled, the gain of IF filter can be set to three levels using the
Filter_Gain field, R9_DB[20:21]. The filter gain is adjusted
automatically, if the AGC loop is enabled.
LNA MODE
(R6_DB15)
MIXER LINEARITY
(R6_DB18)
LNA CURRENT
(R6_DB[16:17])
LNA GAIN
(R9_DB[20:21])
LNA/MIXER ENABLE
(R8_DB6)
Figure 28. ADF7020 RF Front End
The LNA is followed by a quadrature down conversion mixer,
that converts the RF signal to the IF frequency of 200 kHz.
It is important to consider that the output frequency of the
synthesizer must be programmed to a value 200 kHz below
the center frequency of the received channel.
Table 5. LNA/Mixer Modes
Mixer
LNA Mode LNA Gain Value Linearity
(R6_DB15) (R9_DB[20:21]) (R6_DB18) fDEV = 10 kHz)
Sensitivity
(DR = 9.6 kbps,
Rx Current
Consumption
(mA)
Input IP3
(dBm)
Receiver Mode
High Sensitivity Mode (Default)
RxMode2
Low Current Mode
Enhanced Linearity Mode
RxMode5
0
1
1
1
1
0
30
10
3
3
10
30
0
0
0
1
1
1
−110.5
−104
−94
−88
−98
21
20
19
19
20
21
−24
−13.5
−5
−3
−10
−20
RxMode6
−107
Rev. D | Page 20 of 48
Data Sheet
ADF7020
This wait time can be adjusted to speed up this settling by
adjusting the appropriate parameters.
RSSI/AGC
The RSSI is implemented as a successive compression log amp
following the baseband channel filtering. The log amp achieves
3 dB log linearity. It also doubles as a limiter to convert the
signal-to-digital levels for the FSK demodulator. The RSSI itself
is used for amplitude shift keying (ASK) demodulation. In ASK
mode, extra digital filtering is performed on the RSSI value.
Offset correction is achieved using a switched capacitor integra-
tor in feedback around the log amp. This uses the baseband
offset clock divide. The RSSI level is converted for user
AGC _Wait _Time =
AGC _ DELAY ×SEQ _CLK
XTAL
AGC Settling = AGC_Wait_Time × Number of Gain Changes
Thus, in the worst case, if the AGC loop has to go through all
5 gain changes, AGC_Delay =10, SEQ_CLK = 200 kHz, AGC
Settling = 10 × 5 µs × 5 = 250 µs. Minimum AGC_Wait_Time
needs to be at least 25 µs.
readback and digitally controlled AGC by an 80-level (7-bit)
flash ADC. This level can be converted to input power in dBm.
RSSI Formula (Converting to dBm)
Input_Power [dBm] = −120 dBm + (Readback_Code +
Gain_Mode_Correction) × 0.5
OFFSET
CORRECTION
FSK
DEMOD
where:
1
A
A
A
LATCH
CLK
Readback_Code is given by Bit RV7 to Bit RV1 in the readback
register (see the Readback Format section).
FWR
FWR
FWR
FWR
RSSI
ASK
DEMOD
Gain_Mode_Correction is given by the values in Table 6.
ADC
R
LNA gain and filter gain (LG2/LG1, FG2/FG1) are also
obtained from the readback register.
NOTES
1. FWR = FULL WAVE RECTIFIER
Figure 29. RSSI Block Diagram
Table 6. Gain Mode Correction
LNA Gain
(LG2, LG1)
Filter Gain
(FG2, FG1)
RSSI Thresholds
Gain Mode Correction
When the RSSI is above AGC_HIGH_THRESHOLD, the gain
is reduced. When the RSSI is below AGC_LOW_THRESHOLD,
the gain is increased. A delay (AGC_DELAY) is programmed
to allow for settling of the loop. The user programs the two
threshold values (recommended defaults of 30 and 70) and the
delay (default of 10). The default AGC setup values should be
adequate for most applications. The threshold values must be
chosen to be more than 30 apart for the AGC to operate
correctly.
H (1,1)
M (1,0)
M (1,0)
M (1,0)
L (0,1)
H (1,0)
H (1,0)
M (0,1)
L (0,0)
L (0,0)
L (0,0)
0
24
45
63
90
105
EL (0,0)
An additional factor should be introduced to account for losses
in the front-end matching network/antenna.
FSK DEMODULATORS ON THE ADF7020
Offset Correction Clock
The two FSK demodulators on the ADF7020 are
In Register 3, the user should set the BB offset clock divide bits
R3_DB[4:5] to give an offset clock between 1 MHz and 2 MHz.
•
•
FSK correlator/demodulator
Linear demodulator
BBOS_CLK (Hz) = XTAL/(BBOS_CLK_DIVIDE)
where BBOS_CLK_DIVIDE can be set to 4, 8, or 16.
AGC Information and Timing
Select these using the demodulator select bits, R4_DB[4:5].
FSK CORRELATOR/DEMODULATOR
AGC is selected by default, and operates by selecting the appropri-
ate LNA and filter gain settings for the measured RSSI level. It
is possible to disable AGC by writing to Register 9 if entering
one of the modes listed in Table 5 is desired, for example. The
time for the AGC circuit to settle and, therefore, the time to
take an accurate RSSI measurement is typically 150 µs, although
this depends on how many gain settings the AGC circuit has to
cycle through. After each gain change, the AGC loop waits for
a programmed time to allow transients to settle.
The quadrature outputs of the IF filter are first limited and then
fed to a pair of digital frequency correlators that perform band-
pass filtering of the binary FSK frequencies at (IF + fDEV) and
(IF − fDEV). Data is recovered by comparing the output levels
from each of the two correlators. The performance of this fre-
quency discriminator approximates that of a matched filter
detector, which is known to provide optimum detection in
the presence of additive white Gaussian noise (AWGN).
Rev. D | Page 21 of 48
ADF7020
Data Sheet
FREQUENCY CORRELATOR
IF
SLICER
The discriminator BW is controlled in Register 6 by
Bit R6_DB[4:13] and is defined as
RxDATA
RxCLK
I
DEMOD _CLK K
LIMITERS
Q
Discriminator _ BW
800103
IF – fDEV
IF + fDEV
where:
0
DEMOD_CLK is as defined in the Register 3—Receiver Clock
Register section, second comment.
R3_DB[8:15]
R6_DB[4:13] R6_DB[14]
Figure 30. FSK Correlator/Demodulator Block Diagram
K = Round(200 × 103/FSK Deviation)
Postdemodulator Filter
To optimize the coefficients of the FSK correlator, two addi-
tional bits, R6_DB14 and R6_DB29, must be assigned. The
value of these bits depends on whether K (as defined above) is
odd or even. These bits are assigned according to Table 7 and
Table 8.
A second-order, digital low-pass filter removes excess noise from
the demodulated bit stream at the output of the discriminator.
The bandwidth of this postdemodulator filter is programmable
and must be optimized for the user’s data rate. If the bandwidth
is set too narrow, performance is degraded due to intersymbol
interference (ISI). If the bandwidth is set too wide, excess noise
degrades the receiver’s performance. Typically, the 3 dB bandwidth
of this filter is set at approximately 0.75 times the user’s data rate,
using Bits R4_DB[6:15].
Table 7. When K Is Even
K
K/2
R6_DB14
R6_DB29
Even
Even
Even
Odd
0
0
0
1
Bit Slicer
Table 8. When K Is Odd
The received data is recovered by the threshold detecting the
output of the postdemodulator low-pass filter. In the correlator/
demodulator, the binary output signal levels of the frequency
discriminator are always centered on 0. Therefore, the slicer
threshold level can be fixed at 0, and the demodulator perform-
ance is independent of the run-length constraints of the transmit
data bit stream. This results in robust data recovery, which does
not suffer from the classic baseline wander problems that exist in
the more traditional FSK demodulators.
K
(K + 1)/2
R6_DB14
R6_DB29
Odd
Odd
Even
Odd
1
1
0
1
Postdemodulator Bandwidth Register Settings
The 3 dB bandwidth of the postdemodulator filter is controlled
by Bits R4_DB[6:15] and is given by
210 2π fCUTOFF
Postdemod_BW_Setting
DEMOD_CLK
Frequency errors are removed by an internal AFC loop that
measures the average IF frequency at the limiter output and
applies a frequency correction value to the fractional-N
synthesizer. This loop should be activated when the frequency
errors are greater than approximately 40% of the transmit
frequency deviation (see the AFC section).
where fCUTOFF is the target 3 dB bandwidth in Hz of the post-
demodulator filter. This should typically be set to 0.75 times the
data rate (DR).
Some sample settings for the FSK correlator/demodulator are
DEMOD_CLK = 5 MHz
DR = 9.6 kbps
Data Synchronizer
An oversampled digital PLL is used to resynchronize the
received bit stream to a local clock. The oversampled clock rate
of the PLL (CDR_CLK) must be set at 32 times the data rate.
See the Register 3—Receiver Clock Register Comments section
for a definition of how to program. The clock recovery PLL can
accommodate frequency errors of up to 2%.
f
DEV = 20 kHz
Therefore,
f
CUTOFF = 0.75 × 9.6 × 103 Hz
Postdemod_BW_Setting = 211 π 7.2 × 103 Hz/(5 MHz)
Postdemod_BW_Setting = Round(9.26) = 9
and
FSK Correlator Register Settings
To enable the FSK correlator/demodulator, Bits R4_DB[5:4] should
be set to 01. To achieve best performance, the bandwidth of the
FSK correlator must be optimized for the specific deviation
frequency that is used by the FSK transmitter.
K = Round(200 kHz)/20 kHz) = 10
Discriminator_BW = (5 MHz × 10)/(800 × 103) = 62.5 = 63
(rounded to the nearest integer)
Rev. D | Page 22 of 48
Data Sheet
ADF7020
ASK/OOK Operation
Table 9. Register Settings1
Setting Name
ASK/OOK demodulation is activated by setting Bits R4_DB[4:5]
to 10.
Register Address
R4_DB[6:15]
R6_DB[4:13]
R6_DB14
Value
0x09
0x3F
0
Postdemod_BW_Setting
Discriminator_BW
Dot_Product
Digital filtering and envelope detecting the digitized RSSI input
via MUX 1, as shown in Figure 31, performs ASK/OOK
demodulation. The bandwidth of the digital filter must be
optimized to remove any excess noise without causing ISI in the
received ASK/OOK signal.
RxData_Invert
R6_DB29
1
1 The latest version of the ADF7020 configuration software can aid in
calculating register settings.
LINEAR FSK DEMODULATOR
The 3 dB bandwidth of this filter is typically set at approximately
0.75 times the user data rate and is assigned by R4 _DB[6:15] as
Figure 31 shows a block diagram of the linear FSK demodulator.
210 2 fCUTOFF
Postdemod _ BW _Setting
DEMOD_CLK
MUX 1
SLICER
ADC RSSI OUTPUT
7
LEVEL
I
RxDATA
where fCUTOFF is the target 3 dB bandwidth in Hz of the
IF
postdemodulator filter.
LIMITER
Q
It is also recommended to adjust the peak response factor to 6
in Register 10 for robust operation over the full input range.
This improves the receiver’s AM immunity performance.
FREQUENCY
READBACK
AND
FREQUENCY
LINEAR DISCRIMINATOR
AFC LOOP
AFC
R4_DB[6:15]
The ADF7020 supports a real-time AFC loop, which is used to
remove frequency errors that can arise due to mismatches between
the transmit and receive crystals. This uses the frequency
discriminator block, as described in the Linear FSK Demodulator
section (see Figure 31). The discriminator output is filtered and
averaged to remove the FSK frequency modulation, using a
combined averaging filter and envelope detector. In FSK mode,
the output of the envelope detector provides an estimate of the
average IF frequency.
Figure 31. Block Diagram of Frequency Measurement System and
ASK/OOK/Linear FSK Demodulator
This method of frequency demodulation is useful when very
short preamble length is required, and the system protocol
cannot support the overhead of the settling time of the internal
feedback AFC loop settling.
A digital frequency discriminator provides an output signal that
is linearly proportional to the frequency of the limiter outputs.
The discriminator output is then filtered and averaged using a
combined averaging filter and envelope detector. The demodu-
lated FSK data is recovered by threshold-detecting the output of
the averaging filter, (see Figure 31). In this mode, the slicer
output shown in Figure 31 is routed to the data synchronizer
PLL for clock synchronization. To enable the linear FSK
demodulator, set Bits R4_DB[4:5] to 00.
Two methods of AFC, external and internal, are supported on
the ADF7020 (in FSK mode only).
External AFC
The user reads back the frequency information through the
ADF7020 serial port and applies a frequency correction value to
the fractional-N synthesizer’s N divider.
The 3 dB bandwidth of the postdemodulation filter is set in the
same way as the FSK correlator/demodulator, which is set in
R4_DB[6:15] and is defined as
The frequency information is obtained by reading the 16-bit
signed AFC_READBACK, as described in the Readback Format
section, and applying the following formula:
210 2 fCUTOFF
Postdemod _ BW _Setting
DEMOD_CLK
FREQ_RB [Hz] = (AFC_READBACK × DEMOD_CLK)/215
Note that while the AFC_READBACK value is a signed number,
under normal operating conditions, it is positive. The frequency
error can be calculated from
where fCUTOFF is the target 3 dB bandwidth in Hz of the
postdemodulator filter. DEMOD_CLK is as defined in the
Register 3—Receiver Clock Register section, second comment.
FREQ_Error [Hz] = FREQ_RB (Hz) − 200 kHz
Thus, in the absence of frequency errors, the FREQ_RB value is
equal to the IF frequency of 200 kHz.
Rev. D | Page 23 of 48
ADF7020
Data Sheet
Internal AFC
AUTOMATIC SYNC WORD RECOGNITION
The ADF7020 supports a real-time internal automatic
frequency control loop. In this mode, an internal control
loop automatically monitors the frequency error and adjusts
the synthesizer N divider using an internal PI control loop.
The ADF7020 also supports automatic detection of the sync or
ID fields. To activate this mode, the sync (or ID) word must be
preprogrammed into the ADF7020. In receive mode, this
preprogrammed word is compared to the received bit stream
and, when a valid match is identified, the external pin
INT/LOCK is asserted by the ADF7020.
The internal AFC control loop parameters are controlled in
Register 11. The internal AFC loop is activated by setting
R11_DB20 to 1. A scaling coefficient must also be entered,
based on the crystal frequency in use. This is set up in
Bits R11_DB[4:19] and should be calculated using
This feature can be used to alert the microprocessor that a valid
channel has been detected. It relaxes the computational require-
ments of the microprocessor and reduces the overall power
consumption. The INT/LOCK is automatically deasserted again
after nine data clock cycles.
AFC_Scaling_Coefficient = (500 × 224)/XTAL
Therefore, using a 10 MHz XTAL yields an AFC scaling
coefficient of 839.
The automatic sync/ID word detection feature is enabled by
selecting Demodulator Mode 2 or Demodulator Mode 3 in the
demodulator setup register. Do this by setting Bits R4_DB[25:23] =
010 or 011. Bits R5_DB[4:5] are used to set the length of the
sync/ID word, which can be 12, 16, 20, or 24 bits long. The
transmitter must transmit the MSB of the sync byte first and the
LSB last to ensure proper alignment in the receiver sync byte
detection hardware.
AFC Performance
The improved sensitivity performance of the Rx when AFC is
enabled and in the presence of frequency errors is shown in
Figure 18. The maximum AFC frequency range is 50 kHz,
which corresponds to 58 ppm at 868 MHz. This is the total
error tolerance allowed in the link. For example, in a point-to-
point system, AFC can compensate for two 29 ppm crystals or
one 50 ppm crystal and one 8 ppm TCXO.
For systems using forward error correction (FEC), an error
tolerance parameter can also be programmed that accepts a
valid match when up to three bits of the word are incorrect. The
error tolerance value is assigned in Bits R5_DB[6:7].
AFC settling typically takes 48 bits to settle within 1 kHz. This
can be improved by increasing the postdemodulator bandwidth
in Register 4 at the expense of Rx sensitivity.
When AFC errors have been removed using either the internal
or external AFC, further improvement in the receiver’s sensi-
tivity can be obtained by reducing the IF filter bandwidth using
Bits R1_DB[22:23].
Rev. D | Page 24 of 48
Data Sheet
ADF7020
APPLICATIONS INFORMATION
A first-order implementation of the matching network can be
obtained by understanding the arrangement as two L type
matching networks in a back-to-back configuration. Due to the
asymmetry of the network with respect to ground, a compromise
between the input reflection coefficient and the maximum
differential signal swing at the LNA input must be established.
The use of appropriate CAD software is strongly recommended
for this optimization.
LNA/PA MATCHING
The ADF7020 exhibits optimum performance in terms of
sensitivity, transmit power, and current consumption only if its
RF input and output ports are properly matched to the antenna
impedance. For cost-sensitive applications, the ADF7020 is
equipped with an internal Rx/Tx switch that facilitates the use
of a simple combined passive PA/LNA matching network.
Alternatively, an external Rx/Tx switch, such as the Analog
Devices ADG919, can be used. It yields a slightly improved
receiver sensitivity and lower transmitter power consumption.
Depending on the antenna configuration, the user may need a
harmonic filter at the PA output to satisfy the spurious emission
requirement of the applicable government regulations. The
harmonic filter can be implemented in various ways, such as a
discrete LC pi or T-stage filter. Dielectric low-pass filter compo-
nents, such as the LFL18924MTC1A052 (for operation in the
915 MHz and 868 MHz band) by Murata Manufacturing, Co.,
Ltd., represent an attractive alternative to discrete designs.
AN-917 describes how to replace the Murata dielectric filter
with an LC filter if desired.
External Rx/Tx Switch
Figure 32 shows a configuration using an external Rx/Tx switch.
This configuration allows an independent optimization of the
matching and filter network in the transmit and receive path
and is, therefore, more flexible and less difficult to design than
the configuration using the internal Rx/Tx switch. The PA is
biased through Inductor L1, while C1 blocks dc current. Both
elements, L1 and C1, also form the matching network, which
transforms the source impedance into the optimum PA load
impedance, ZOPT_PA.
The immunity of the ADF7020 to strong out-of-band interference
can be improved by adding a band-pass filter in the Rx path.
Apart from discrete designs, SAW or dielectric filter components,
such as the SAFCH869MAM0T00 or SAFCH915MAL0N00,
both by Murata, are well suited for this purpose. Alternatively,
the ADF7020 blocking performance can be improved by
selecting the high linearity mode, as described in Table 5.
V
BAT
L1
C1
PA_OUT
OPTIONAL
LPF
PA
ANTENNA
Z
_PA
OPT
Internal Rx/Tx Switch
Z
_RFIN
IN
C
A
OPTIONAL
BPF
RFIN
Figure 33 shows the ADF7020 in a configuration where the
internal Rx/Tx switch is used with a combined LNA/PA
matching network. This is the configuration used in the
ADF7020-XDBX evaluation boards. For most applications, the
slight performance degradation of 1 dB to 2 dB caused by the
internal Rx/Tx switch is acceptable, allowing the user to take
advantage of the cost saving potential of this solution. The
design of the combined matching network must compensate for
the reactance presented by the networks in the Tx and the Rx
paths, taking the state of the Rx/Tx switch into consideration.
(SAW)
L
LNA
A
RFINB
ADG919
Rx/Tx – SELECT
Z
_RFIN
IN
C
B
ADF7020
Figure 32. ADF7020 with External Rx/Tx Switch
ZOPT_PA depends on various factors, such as the required
output power, the frequency range, the supply voltage range,
and the temperature range. Selecting an appropriate ZOPT_PA
helps to minimize the Tx current consumption in the
application. Application Note AN-767 contains a number of
V
BAT
L1
C1
PA_OUT
PA
Z
OPT_PA values for representative conditions. Under certain
conditions, however, it is recommended that a suitable ZOPT_PA
value be obtained by means of a load-pull measurement.
ANTENNA
Z
_PA
OPT
OPTIONAL
BPF OR LPF
Z
_RFIN
IN
C
A
RFIN
Due to the differential LNA input, the LNA matching network
must be designed to provide both a single-ended-to-differential
conversion and a complex conjugate impedance match. The
network with the lowest component count that can satisfy these
requirements is the configuration shown in Figure 32, which
consists of two capacitors and one inductor.
L
LNA
A
RFINB
Z
_RFIN
IN
C
B
ADF7020
Figure 33. ADF7020 with Internal Rx/Tx Switch
Rev. D | Page 25 of 48
ADF7020
Data Sheet
The procedure typically requires several iterations until an
acceptable compromise is reached. The successful implementation
of a combined LNA/PA matching network for the ADF7020 is
critically dependent on the availability of an accurate electrical
model for the PC board. In this context, the use of a suitable
CAD package is strongly recommended. To avoid this effort,
however, a small form-factor reference design for the ADF7020
is provided, including matching and harmonic filter components.
Gerber files and schematics are available at www.analog.com.
Calibration Procedure and Setup
The image rejection calibration works by connecting an
external RF signal to the RF input port. The external RF signal
should be set at the image frequency and the filter rejection
measured by monitoring the digital RSSI readback. As the
image rejection is improved by adjusting the I/Q Gain and
phase, the RSSI reading reduces.
The magnitude of the phase adjust is set by using the IR_PHASE_
ADJUST bits (R10_DB[24:27]). This correction can be applied
to either the I channel or Q channel, by toggling bit (R10_DB28).
IMAGE REJECTION CALIBRATION
The image channel in the ADF7020 is 400 kHz below the
desired signal. The polyphase filter rejects this image with an
asymmetric frequency response. The image rejection
performance of the receiver is dependent on how well matched
the I and Q signals are in amplitude, and how well matched the
quadrature is between them (that is, how close to 90º apart they
are.) The uncalibrated image rejection performance is
approximately 30 dB. However, it is possible to improve this
performance by as much as 20 dB by finding the optimum I/Q
gain and phase adjust settings.
The magnitude of the I/Q gain is adjusted by the IR_GAIN_
ADJUST bits (R10_DB[16:20]). This correction can be applied
to either the I or Q channel using bit (R10_DB22), while the
GAIN/ATTENUATE bit (R10_DB21) sets whether the gain
adjustment defines a gain or attenuation adjust.
The calibration results are valid over changes in the ADF7020
supply voltage. However, there is some variation with temperature.
A typical plot of variation in image rejection over temperature
after initial calibrations at +25°C, −40°C, and +85°C is shown in
Figure 35. The internal temperature sensor on the ADF7020 can
be used to determine if a new IR calibration is required.
ADF7020
RFIN
EXTERNAL
SIGNAL
SOURCE
MATCHING
LNA
RFINB
POLYPHASE
IF FILTER
RSSI/
LOG AMP
7-BIT ADC
PHASE ADJUSTMENT
I
Q
FROM LO
SERIAL
INTERFACE
4
PHASE ADJUST
REGISTER 10
RSSI READBACK
4
GAIN ADJUST
REGISTER 10
MICROCONTROLLER
I/Q GAIN/PHASE ADJUST AND
RSSI MEASUREMENT
ALGORITHM
Figure 34. Image Rejection Calibration Using the Internal Calibration Source and a Microcontroller
Rev. D | Page 26 of 48
Data Sheet
ADF7020
60
DEVICE PROGRAMMING AFTER INITIAL
POWER-UP
CAL AT +25°C
50
Table 10 lists the minimum number of writes needed to set up
the ADF7020 in either Tx or Rx mode after CE is brought high.
Additional registers can also be written to tailor the part to a
particular application, such as setting up sync byte detection or
enabling AFC. When going from Tx to Rx or vice versa, the
user needs to write only to the N Register to alter the LO by
200 kHz and to toggle the Tx/Rx bit.
40
30
20
10
0
CAL AT +85°C
CAL AT –40°C
V
= 3.0V
IF BW = 25kHz
DD
INTERFERER SIGNAL:
RF FREQ = 429.8MHz
MODULATION = 2FSK
DATA RATE = 9.6kbps,
PRBS11
WANTED SIGNAL:
RF FREQ = 430MHz
MODULATION = 2FSK
DATA RATE = 9.6kbps,
PRBS9
fDEV = 4kHz
LEVEL= –100dBm
Table 10. Minimum Register Writes Required for Tx/Rx Setup
fDEV = 4kHz
Mode
Register
–60
–40
–20
0
20
40
60
80
100
Tx
Reg. 0
Reg. 0
Reg. 1
Reg. 1
Reg. 1
Reg. 2
Reg. 3
Reg. 3
TEMPERATURE (°C)
Rx (OOK)
Reg. 4
Reg. 4
Reg. 6
Reg. 6
Figure 35. Image Rejection Variation with Temperature after Initial
Calibrations at +25°C, −40°C, and +85°C
Rx (G/FSK) Reg. 0
Reg. 0
Tx ↔Rx
TRANSMIT PROTOCOL AND CODING
CONSIDERATIONS
Figure 39 and Figure 40 show the recommended programming
sequence and associated timing for power-up from standby mode.
SYNC
WORD
ID
FIELD
INTERFACING TO MICROCONTROLLER/DSP
PREAMBLE
DATA FIELD
CRC
Low level device drivers are available for interfacing the
ADF7020 to the Analog Devices ADuC84x analog
Figure 36. Typical Format of a Transmit Protocol
microcontrollers, or the Blackfin® ADSP-BF53x DSPs, using the
hardware connections shown in Figure 37 and Figure 38.
A dc-free preamble pattern is recommended for FSK/GFSK/
ASK/OOK demodulation. The recommended preamble pattern
is a dc-balanced pattern such as a 10101010… sequence.
Preamble patterns with longer run-length constraints such as
11001100… can also be used. However, this results in a longer
synchronization time of the received bit stream in the receiver.
ADuC84x
ADF7020
MISO
DATA I/O
MOSI
SCLOCK
SS
DATA CLK
The remaining fields that follow the preamble header do not
have to use dc-free coding. For these fields, the ADF7020 can
accommodate coding schemes with a run-length of up to
several bytes without any performance degradation, for example
several bytes of 0x00 or 0xFF. To help minimize bit errors when
receiving these long runs of continuous 0s or 1s, it is important
to choose a data rate and XTAL combination that minimizes
the error between the actual data rate and the on-board
CDR_CLK/32. For example, if a 9.6 kbps data rate is desired,
then using an 11.0592 MHz XTAL gives a 0% nominal error
between the desired data rate and CDR_CLK/32. AN-915 gives
more details on supporting long run lengths on the ADF7020.
P3.7
CE
P3.2/INT0
P2.4
INT/LOCK
SREAD
SLE
P2.5
GPIO
P2.6
P2.7
SDATA
SCLK
Figure 37. ADuC84x to ADF7020 Connection Diagram
ADSP-BF533
ADF7020
SCK
MOSI
SCLK
SDATA
SREAD
SLE
MISO
PF5
RSCLK1
DT1PRI
DR1PRI
RFS1
DATA CLK
DATA I/O
The ADF7020 can also support Manchester-encoded data for
the entire protocol. Manchester decoding needs to be done on
the companion microcontroller, however. In this case, the
ADF7020 should be set up at the Manchester chip or baud
rate, which is twice the effective data rate.
INT/LOCK
CE
PF6
V
VDD
DDEXT
GND
GND
Figure 38. ADSP-BF533 to ADF7020 Connection Diagram
Rev. D | Page 27 of 48
ADF7020
Data Sheet
Using a sequenced power-on routine like that illustrated in
POWER CONSUMPTION AND BATTERY LIFETIME
CALCULATIONS
Figure 39 can reduce the IAVG_ON current and, hence, reduce the
overall power consumption. When used in conjunction with a
large duty-cycle or large tOFF, this can result in significantly
increased battery life. Analog Devices, Inc.’s free design tool,
ADI SRD Design Studio, can assist in these calculations.
Average Power Consumption can be calculated using
Average Power Consumption = (tON × IAVG_ON + tOFF
×
IPowerDown)/(tON + tOFF)
19mA TO
22mA
14mA
XTAL
t0
3.65mA
2.0mA
AFC
t
10
REG.
REtA1DY t2
AGC/
RSSI
t8
TIME
WR0 WR1
WR3 WR4 WR6
t5 t6 t7
RxDATA
t11
t3
VtC4O
CtD9R
tON
Figure 39. Rx Programming Sequence and Timing Diagram
tOFF
Table 11. Power-Up Sequence Description
Parameter Value Description
Signal to Monitor
t0
2 ms
Crystal starts power-up after CE is brought high. This typically depends
on the crystal type and the load capacitance specified.
CLKOUT pin
t1
10 μs
Time for regulator to power up. The serial interface can be written to after
this time.
Time to write to a single register. Maximum SPI_CLK is 25 MHz.
MUXOUT pin
CVCO pin
t2, t3, t5,
t6, t7
t4
32 × 1/SPI_CLK
1 ms
The VCO can power-up in parallel with the crystal. This depends on the
CVCO capacitance value used. A value of 22 nF is recommended as a
trade-off between phase noise performance and power-up time.
t8
150 μs
This depends on the number of gain changes the AGC loop needs to cycle
through and AGC settings programmed. This is described in more detail
in the AGC Information and Timing section.
Analog RSSI on TEST_A pin
(Available by writing 0x3800 000C)
t9
5 × Bit_Period
This is the time for the clock and data recovery circuit to settle. This typically
requires 5-bit transitions to acquire sync and is usually covered by the
preamble.
t10
48 × Bit_Period This is the time for the automatic frequency control circuit to settle. This
typically requires 48-bit transitions to acquire lock and is usually covered
by an appropriate length preamble.
t11
Packet Length
Number of bits in payload by the bit period.
Rev. D | Page 28 of 48
Data Sheet
ADF7020
15mA TO
30mA
14mA
3.65mA
2.0mA
REG.
REtA1DY t2
TIME
WR0 WR1
WR2
t5
TxDATA
t12
t3
XTALt+4 VCO
tON
tOFF
Figure 40. Tx Programming Sequence and Timing Diagram
Rev. D | Page 29 of 48
ADF7020
Data Sheet
LOOP FILTER
XTAL
REFERENCE
VDD
CVCO
CAP
VDD
1
2
36
35
34
33
32
31
30
29
28
27
26
25
VCOIN
CLKOUT
DATA CLK
DATA I/O
INT/LOCK
VDD2
MATCHING
PIN 1
INDICATOR
CREG1
VDD1
3
VDD
VDD
T-STAGE LC
FILTER
4
ANTENNA
CONNECTION
RFOUT
RFGND
RFIN
5
VDD
6
CREG2
ADCIN
ADF7020
TOP VIEW
(Not to Scale)
7
RFINB
8
R
GND2
LNA
9
VDD4
RSET
CREG4
GND4
SCLK
10
11
12
SREAD
SDATA
SLE
RLNA
RESISTOR
RSET
RESISTOR
Figure 41. Application Circuit
Rev. D | Page 30 of 48
Data Sheet
ADF7020
SERIAL INTERFACE
The serial interface allows the user to program the fourteen
32-bit registers using a 3-wire interface (SCLK, SDATA, and
SLE). Signals should be CMOS compatible. The serial interface
is powered by the regulator and, therefore, is inactive when
CE is low.
RSSI Readback
The RSSI readback operation yields valid results in Rx mode
with ASK or FSK signals. The format of the readback word is
shown in Figure 42. It comprises the RSSI level information
(Bit RV1 to Bit RV7), the current filter gain (FG1, FG2), and the
current LNA gain (LG1, LG2) setting. The filter and LNA gain
are coded in accordance with the definitions in Register 9. With
the reception of ASK modulated signals, averaging of the
measured RSSI values improves accuracy. The input power can
be calculated from the RSSI readback value as outlined in the
RSSI/AGC section.
Data is clocked into the register, MSB first, on the rising edge
of each clock (SCLK). Data is transferred to one of fourteen
latches on the rising edge of SLE. The destination latch is
determined by the value of the four control bits (C4 to C1).
These are the bottom four LSBs, DB3 to DB0, as shown in the
timing diagram in Figure 3.
Battery Voltage/ADCIN/Temperature Sensor Readback
READBACK FORMAT
These three ADC readback values are valid by just enabling the
ADC in Register 8 without writing to the other registers. The
battery voltage is measured at Pin VDD4. The readback
information is contained in Bit RV1 to Bit RV7. This also
applies for the readback of the voltage at the ADCIN pin and
the temperature sensor. From the readback information, the
battery, ADCIN voltage or temperature can be obtained using
The readback operation is initiated by writing a valid control
word to the readback register and setting the readback enable
bit (R7_DB8 = 1). The readback can begin after the control
word has been latched with the SLE signal. SLE must be kept
high while the data is being read out. Each active edge at the
SCLK pin clocks the readback word out successively at the
SREAD pin (see Figure 42), starting with the MSB first. The
data appearing at the first clock cycle following the latch
operation must be ignored. The last (eighteenth) SCLK edge
puts the SREAD pin back in three-state.
V
BATTERY = (Battery_Voltage_Readback)/21.1
ADCIN = (ADCIN_Voltage_Readback)/42.1
V
Temperature =
−40°C + (68.4 − Temperature_Sensor_Readback) × 9.32
AFC Readback
The AFC readback is valid only during the reception of FSK
signals with either the linear or correlator demodulator active.
The AFC readback value is formatted as a signed 16-bit integer
comprising Bit RV1 to Bit RV16 and is scaled according to the
following formula:
Silicon Revision Readback
The silicon revision word is coded with four quartets in BCD
format. The product code (PC) is coded with three quartets
extending from Bit RV5 to Bit RV16. The revision code (RV) is
coded with one quartet extending from Bit RV1 to Bit RV4. The
product code for the ADF7020 should read back as PC = 0x200.
The current revision code should read as RV = 0x8.
FREQ_RB [Hz] = (AFC_READBACK × DEMOD_CLK)/215
In the absence of frequency errors, the FREQ_RB value is equal
to the IF frequency of 200 kHz. Note that, for the AFC readback
to yield a valid result, the down-converted input signal must not
fall outside the bandwidth of the analog IF filter. At low input
signal levels, the variation in the readback value can be improved
by averaging.
Filter Calibration Readback
The filter calibration readback word is contained in Bit RV1 to
Bit RV8 and is for diagnostic purposes only. Using the automatic
filter calibration function, accessible through Register 6, is
recommended. Before filter calibration is initiated, decimal 32
should be read back as the default value.
READBACK MODE
READBACK VALUE
DB15 DB14 DB13 DB12 DB11 DB10 DB9
DB8
DB7
RV8
FG1
DB6
RV7
RV7
DB5
RV6
RV6
DB4
RV5
RV5
DB3
RV4
RV4
DB2
RV3
RV3
DB1
RV2
RV2
DB0
RV1
RV1
AFC READBACK
RSSI READBACK
RV16 RV15 RV14 RV13 RV12 RV11 RV10 RV9
X
X
X
X
X
X
X
X
X
X
LG2
X
LG1
X
FG2
X
BATTERY VOLTAGE/ADCIN/
TEMP. SENSOR READBACK
X
RV7
RV6
RV5
RV4
RV3
RV2
RV1
SILICON REVISION
RV16 RV15 RV14 RV13 RV12 RV11 RV10 RV9
RV8
RV8
RV7
RV7
RV6
RV6
RV5
RV5
RV4
RV4
RV3
RV3
RV2
RV2
RV1
RV1
FILTER CAL READBACK
0
0
0
0
0
0
0
0
Figure 42. Readback Value Table
Rev. D | Page 31 of 48
ADF7020
Data Sheet
REGISTERS
REGISTER 0—N REGISTER
ADDRESS
BITS
MUXOUT
8-BIT INTEGER-N
15-BIT FRACTIONAL-N
TRANSMIT/
RECEIVE
FRACTIONAL
DIVIDE RATIO
TR1
M15 M14 M13
.
M3
M2
M1
0
1
TRANSMIT
RECEIVE
0
0
0
.
.
.
1
1
1
1
0
0
0
.
.
.
1
1
1
1
0
0
0
.
.
.
1
1
1
1
.
.
.
.
.
.
.
.
.
.
0
0
0
.
.
.
1
1
1
1
0
0
1
.
.
.
0
0
1
1
0
1
0
.
.
.
0
1
0
1
0
1
2
.
.
.
PLE1 PLL ENABLE
0
1
PLL OFF
PLL ON
32,764
32,765
32,766
32,767
M3
M2
M1
MUXOUT
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
REGULATOR READY (DEFAULT)
R DIVIDE
R OUTPUT
N DIVIDER OUTPUT
DIGITAL LOCK DETECT
ANALOG LOCK DETECT
THREE-STATE
PLL TEST MODES
Σ-Δ TEST MODES
N COUNTER
N8
N7
N6
N5
N4
N3
N2
N1
DIVIDE RATIO
0
0
.
0
0
.
0
1
.
1
0
.
1
0
.
1
0
.
1
0
.
1
0
.
31
32
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
1
1
1
1
1
0
1
253
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
254
255
Figure 43. Register 0—N Register
Register 0—N Register Comments
•
•
•
The Tx/Rx bit (R0_DB27) configures the part in Tx or Rx mode and controls the state of the internal Tx/Rx switch.
XTAL
R
Fractional_ N
fOUT
=
×(Integer _ N +
)
215
If operating in 433 MHz band, with the VCO Band bit set, the desired frequency, fOUT, should be programmed to be twice the desired
operating frequency, due to removal of the divide-by-2 stage in the feedback path.
Rev. D | Page 32 of 48
Data Sheet
ADF7020
REGISTER 1—OSCILLATOR/FILTER REGISTER
CLOCKOUT
DIVIDE
ADDRESS
BITS
VCO BIAS
R COUNTER
FREQUENCY
RF R COUNTER
DIVIDE RATIO
X1 XTAL OSC
VA2 VA1
R3 R2 R1
OF OPERATION
850 TO 920
860 TO 930
870 TO 940
880 TO 950
0
1
OFF
ON
0
0
.
0
1
.
1
0
.
1
2
.
0
0
1
1
0
1
0
1
VCO Band
(MHz)
.
.
.
.
V1
.
.
.
.
0
1
862 TO 956
431 TO 478
1
1
1
7
VCO BIAS
CURRENT
VB4
VB3 VB2 VB1
XTAL
DOUBLER
0
0
0
.
0
0
0
.
0
0
1
.
0
1
0
.
0.125mA
0.375mA
0.625mA
D1
0
1
DISABLE
ENABLED
1
1
1
1
3.875mA
CLKOUT
DIVIDE RATIO
CL4
CL3
CL2
CL1
OFF
0
0
0
.
0
0
0
.
0
0
1
.
0
1
0
.
FILTER
BANDWIDTH
CP2 CP1
I
(mA)
CP
IR2 IR1
2
4
.
0
0
1
1
0
1
0
1
0.3
0
0
1
1
0
1
0
1
100kHz
150kHz
200kHz
NOT USED
0.9
1.5
2.1
.
.
.
.
.
.
.
.
.
.
30
1
1
1
1
Figure 44. Register 1—Oscillator/Filter Register
Register 1—Oscillator/Filter Register Comments
•
The VCO Adjust Bits R1_DB[20:21] should be set to 0 for operation in the 862 MHz to 870 MHz band and set to 3 for operation in
the 902 MHz to 928 MHz band.
•
The VCO bias setting should be 0xA for operation in the 862 MHz to 870 MHz and 902 MHz to 928 MHz bands. All VCO gain
numbers are specified for these VCO Adjust and Bias settings.
Rev. D | Page 33 of 48
ADF7020
Data Sheet
REGISTER 2—TRANSMIT MODULATION REGISTER (ASK/OOK MODE)
GFSK MOD
CONTROL
MODULATION
SCHEME
ADDRESS
BITS
PA BIAS
MODULATION PARAMETER
POWER AMPLIFIER
PE1 POWER AMPLIFIER
0
1
OFF
ON
IC2 IC1 MC3 MC2 MC1
X
X
X
X
X
MUTE PA UNTIL
MP1 LOCK DETECT HIGH
DI1
0
1
TxDATA
TxDATA
0
1
OFF
ON
PA2 PA1 PA BIAS
S3
S2
S1
MODULATION SCHEME
0
0
1
1
0
1
0
1
5µA
7µA
9µA
11µA
0
0
0
0
1
0
0
1
1
1
0
1
0
1
1
FSK
GFSK
ASK
OOK
GOOK
POWER AMPLIFIER OUTPUT LOW LEVEL
POWER AMPLIFIER OUTPUT HIGH LEVEL
D6
D5
.
D2
D1
P6
.
.
P2
P1
X
0
0
0
0
.
X
X
0
0
.
.
.
1
.
.
.
.
.
.
.
.
X
X
0
0
1
.
X
X
0
1
0
.
OOK MODE
PA OFF
–16.0dBm
–16 + 0.45dBm
–16 + 0.90dBm
.
0
0
0
0
.
.
.
.
.
.
.
1
.
.
.
.
.
.
.
X
0
0
1
.
X
0
1
0
.
PA OFF
–16.0dBm
–16 + 0.45dBm
–16 + 0.90dBm
.
.
.
1
.
1
.
1
.
1
.
1
.
1
.
13dBm
13dBm
Figure 45. Register 2—Transmit Modulation Register (ASK/OOK Mode)
Register 2—Transmit Modulation Register (ASK/OOK Mode) Comments
•
See the Transmitter section for a description of how the PA bias affects the power amplifier level. The default level is 9 µA.
If maximum power is needed, program this value to 11 µA.
•
•
See Figure 13.
D7, D8, and D9 are don’t care bits.
Rev. D | Page 34 of 48
Data Sheet
ADF7020
REGISTER 2—TRANSMIT MODULATION REGISTER (FSK MODE)
GFSK MOD
CONTROL
MODULATION
SCHEME
ADDRESS
BITS
PA BIAS
MODULATION PARAMETER
POWER AMPLIFIER
PE1 POWER AMPLIFIER
0
1
OFF
ON
IC2 IC1 MC3 MC2 MC1
X
X
X
X
X
MUTE PA UNTIL
MP1 LOCK DETECT HIGH
FOR FSK MODE,
DI1
D9
.
D3
D2
D1
F DEVIATION
0
1
TxDATA
TxDATA
0
1
OFF
ON
0
0
0
0
.
.
.
.
.
.
.
0
0
0
0
.
0
0
1
1
.
0
1
0
1
.
PLL MODE
1 × fSTEP
2 × fSTEP
3 × fSTEP
.
PA2 PA1 PA BIAS
S3
S2
S1
MODULATION SCHEME
0
0
1
1
0
1
0
1
5µA
7µA
9µA
11µA
1
1
1
1
511 × fSTEP
0
0
0
0
1
0
0
1
1
1
0
1
0
1
1
FSK
GFSK
ASK
OOK
GOOK
POWER AMPLIFIER OUTPUT LEVEL
P6
.
.
P2
P1
0
0
0
0
.
.
.
.
.
.
.
1
.
.
.
.
.
.
.
X
0
0
1
.
X
0
1
0
.
PA OFF
–16.0dBm
–16 + 0.45dBm
–16 + 0.90dBm
.
.
.
1
.
1
.
1
13dBm
Figure 46. Register 2—Transmit Modulation Register (FSK Mode)
Register 2—Transmit Modulation Register (FSK Mode) Comments
•
•
•
f
STEP = PFD/214.
When operating in the 431 MHz to 478 MHz band, fSTEP = PFD/215.
PA bias default = 9 µA.
Rev. D | Page 35 of 48
ADF7020
Data Sheet
REGISTER 2—TRANSMIT MODULATION REGISTER (GFSK/GOOK MODE)
GFSK MOD
CONTROL
MODULATION
SCHEME
ADDRESS
BITS
PA BIAS
MODULATION PARAMETER
POWER AMPLIFIER
PE1 POWER AMPLIFIER
D7
.
D3
D2
D1
DIVIDER_FACTOR
0
1
OFF
ON
0
0
0
0
.
.
.
.
.
.
.
0
0
0
0
.
0
0
1
1
.
0
1
0
1
.
INVALID
1
2
3
.
MUTE PA UNTIL
MP1 LOCK DETECT HIGH
1
1
1
1
127
DI1
0
1
TxDATA
TxDATA
0
1
OFF
ON
PA2 PA1 PA BIAS
GAUSSIAN – OOK
MODE
S3
S2
S1
MODULATION SCHEME
D9
D8
0
0
1
1
0
1
0
1
5µA
7µA
9µA
11µA
0
0
0
0
1
0
0
1
1
1
0
1
0
1
1
FSK
GFSK
ASK
OOK
GOOK
0
0
1
1
0
1
0
1
NORMAL MODE
OUTPUT BUFFER ON
BLEED CURRENT ON
BLEED/BUFFER ON
IC2 IC1 INDEX_COUNTER
POWER AMPLIFIER OUTPUT LEVEL
0
0
1
1
0
1
0
1
16
32
64
128
P6
.
.
P2
P1
0
0
0
0
.
.
.
.
.
.
.
1
.
.
.
.
.
.
.
X
0
0
1
.
X
0
1
0
.
PA OFF
–16.0dBm
–16 + 0.45dBm
–16 + 0.90dBm
.
.
MC3 MC2 MC1 GFSK_MOD_CONTROL
.
1
.
1
.
1
13dBm
0
0
.
0
0
.
0
1
.
0
1
.
1
1
1
7
Figure 47. Register 2—Transmit Modulation Register (GFSK/GOOK Mode)
Register 2—Transmit Modulation Register (GFSK/GOOK Mode) Comments
•
•
•
•
GFSK_DEVIATION = (2GFSK_MOD_CONTROL × PFD)/212.
When operating in the 431 MHz to 478 MHz band, GFSK_DEVIATION = (2GFSK_MOD_CONTROL × PFD)/213.
Data Rate = PFD/(INDEX_COUNTER × DIVIDER_FACTOR).
PA Bias default = 9 µA.
Rev. D | Page 36 of 48
Data Sheet
ADF7020
REGISTER 3—RECEIVER CLOCK REGISTER
ADDRESS
BITS
SEQUENCER CLOCK DIVIDE
CDR CLOCK DIVIDE
SK8 SK7
.
.
.
.
.
.
SK3 SK2 SK1 SEQ_CLK_DIVIDE
BK2 BK1 BBOS_CLK_DIVIDE
0
0
.
0
0
.
0
0
.
0
1
.
1
0
.
1
2
.
0
0
1
0
1
x
4
8
16
1
1
1
1
1
1
1
1
0
1
254
255
OK2 OK1 DEMOD_CLK_DIVIDE
0
0
1
1
0
1
0
1
4
1
2
3
FS8
FS7
.
FS3
FS2
FS1 CDR_CLK_DIVIDE
0
0
.
1
1
0
0
.
1
1
.
.
.
.
.
0
0
.
1
1
0
1
.
1
1
1
0
.
0
1
1
2
.
254
255
Figure 48. Register 3—Receiver Clock Register
Register 3—Receiver Clock Register Comments
•
•
•
Baseband offset clock frequency (BBOS_CLK) must be greater than 1 MHz and less than 2 MHz, where
XTAL
BBOS_CLK _ DIVIDE
BBOS_CLK =
The demodulator clock (DEMOD_CLK) must be <12 MHz for FSK and <6 MHz for ASK, where
XTAL
DEMOD _CLK =
DEMOD _CLK _ DIVIDE
Data/clock recovery frequency (CDR_CLK) should be within 2% of (32 × data rate), where
DEMOD _CLK
CDR_CLK =
CDR_CLK _ DIVIDE
Note that this can affect your choice of XTAL, depending on the desired data rate.
•
The sequencer clock (SEQ_CLK) supplies the clock to the digital receive block. It should be close to 100 kHz for FSK and close to
40 kHz for ASK.
XTAL
SEQ _CLK _ DIVIDE
SEQ _CLK =
Rev. D | Page 37 of 48
ADF7020
Data Sheet
REGISTER 4—DEMODULATOR SETUP REGISTER
ADDRESS
BITS
DEMODULATOR LOCK SETTING
POSTDEMODULATOR BW
DEMODULATOR
TYPE
DS2 DS1
0
0
1
1
0
1
0
1
LINEAR DEMODULATOR
CORRELATOR/DEMODULATOR
ASK/OOK
INVALID
DEMOD MODE LM2 LM1 DL8 DEMOD LOCK/SYNC WORD MATCH
INT/LOCK PIN
0
1
2
3
4
5
0
0
0
0
1
1
0
0
1
1
0
1
0
1
0
1
X
SERIAL PORT CONTROL – FREE RUNNING
SERIAL PORT CONTROL – LOCK THRESHOLD
SYNC WORD DETECT – FREE RUNNING
SYNC WORD DETECT – LOCK THRESHOLD
INTERRUPT/LOCK PIN LOCKS THRESHOLD
–
–
OUTPUT
OUTPUT
INPUT
–
DL8 DEMOD LOCKED AFTER DL8–DL1 BITS
MODE5 ONLY
DL8 DL7
.
.
.
.
.
.
DL3 DL2 DL1 LOCK_THRESHOLD_TIMEOUT
0
0
0
.
0
0
0
.
0
0
0
.
0
0
1
.
0
1
0
.
0
1
2
.
1
1
1
1
1
1
1
1
0
1
254
255
Figure 49. Register 4—Demodulator Setup Register
Register 4—Demodulator Setup Register Comments
•
Demodulator Mode 1, Demodulator Mode 3, Demodulator Mode 4, and Demodulator Mode 5 are modes that can be activated to
allow the ADF7020 to demodulate data-encoding schemes that have run-length constraints greater than 7, when using the linear
demodulator.
211 × π× fCUTOFF
Postdemod_BW =
•
•
DEMOD_CLK
where the cutoff frequency (fCUTOFF) of the postdemodulator filter should typically be 0.75 times the data rate.
For Mode 5, Timeout Delay to Lock Threshold = (LOCK_THRESHOLD_SETTING)/SEQ_CLK
where SEQ_CLK is defined in the Register 3—Receiver Clock Register section.
Rev. D | Page 38 of 48
Data Sheet
ADF7020
REGISTER 5—SYNC BYTE REGISTER
CONTROL
BITS
SYNC BYTE SEQUENCE
SYNC BYTE
PL2 PL1 LENGTH
0
0
1
1
0
1
0
1
12 BITS
16 BITS
20 BITS
24 BITS
MATCHING
MT2 MT1 TOLERANCE
0
0
1
1
0
1
0
1
0 ERRORS
1 ERROR
2 ERRORS
3 ERRORS
Figure 50. Register 5—Sync Byte Register
Register 5—Sync Byte Register Comments
•
•
Sync byte detect is enabled by programming Bits R4_DB[25:23] to 010 or 011.
This register allows a 24-bit sync byte sequence to be stored internally. If the sync byte detect mode is selected, then the INT/LOCK
pin goes high when the sync byte is detected in Rx mode. Once the sync word detect signal goes high, it goes low again after nine
data bits.
•
•
The transmitter must transmit the MSB of the sync byte first and the LSB last to ensure proper alignment in the receiver sync byte
detection hardware.
Choose a sync byte pattern that has good autocorrelation properties, for example, 0x123456.
Rev. D | Page 39 of 48
ADF7020
Data Sheet
REGISTER 6—CORRELATOR/DEMODULATOR REGISTER
Rx
RESET
ADDRESS
BITS
IF FILTER DIVIDER
DISCRIMINATOR BW
CA1 FILTER CAL
DP1 DOT PRODUCT
0
1
NO CAL
CALIBRATE
0
1
CROSS PRODUCT
DOT PRODUCT
ML1 MIXER LINEARITY
LG1 LNA MODE
0
1
DEFAULT
HIGH
0
1
DEFAULT
REDUCED GAIN
RxDATA
INVERT
RI1
LI2 LI1 LNA BIAS
800µA (DEFAULT)
RxDATA
RxDATA
0
1
0
0
RxRESET
FILTER CLOCK
DIVIDE RATIO
0
1
NORMAL OPPERATION
DEMOD RESET
FC9
.
FC6 FC5 FC4 FC3 FC2 FC1
0
0
.
.
.
.
.
.
.
.
.
.
0
0
.
0
0
.
0
0
.
0
0
.
0
1
.
1
0
.
1
2
.
.
.
.
.
.
.
.
.
.
RxRESET
.
.
.
.
.
.
0
1
NORMAL OPPERATION
CDR RESET
.
1
.
.
.
.
.
.
1
1
1
1
1
1
511
Figure 51. Register 6—Correlator/Demodulator Register
Register 6—Correlator/Demodulator Register Comments
•
•
•
See the FSK Correlator/Demodulator section for an example of how to determine register settings.
Nonadherence to correlator programming guidelines results in poorer sensitivity.
The filter clock is used to calibrate the IF filter. The filter clock divide ratio should be adjusted so that the frequency is 50 kHz.
The formula is XTAL/FILTER_CLOCK_DIVIDE.
•
The filter should be calibrated only when the crystal oscillator is settled. The filter calibration is initiated every time Bit R6_DB19
is set high.
•
•
Discriminator_BW = (DEMOD_CLK × K)/(800 × 103). See the FSK Correlator/Demodulator section. Maximum value = 600.
When LNA Mode = 1 (reduced gain mode), the Rx is prevented from selecting the highest LNA gain setting. This can be used when
linearity is a concern. See Table 5 for details of the different Rx modes.
Rev. D | Page 40 of 48
Data Sheet
ADF7020
REGISTER 7—READBACK SETUP REGISTER
READBACK
SELECT
ADC
MODE
CONTROL
BITS
DB1
DB0
DB7
RB2
DB8
RB3
DB6
RB1
DB5
AD2
DB4
AD1
DB3
DB2
C4(0) C3(1) C2(1) C1(1)
RB3 READBACK
AD2 AD1 ADC MODE
0
1
DISABLED
ENABLED
0
0
1
1
0
1
0
1
MEASURE RSSI
BATTERY VOLTAGE
TEMP SENSOR
TO EXTERNAL PIN
RB2 RB1 READBACK MODE
0
0
1
1
0
1
0
1
AFC WORD
ADC OUTPUT
FILTER CAL
SILICON REV
Figure 52. Register 7—Readback Setup Register
Register 7—Readback Setup Register Comments
•
Readback of the measured RSSI value is valid only in Rx mode. To enable readback of the battery voltage, the temperature sensor, or
the voltage at the external pin in Rx mode, AGC function in Register 9 must be disabled. To read back these parameters in Tx mode,
the ADC must first be powered up using Register 8 because this is off by default in Tx mode to save power. This is the recommended
method of using the battery readback function because most configurations typically require AGC.
•
•
Readback of the AFC word is valid in Rx mode only if either the linear demodulator or the correlator/demodulator is active.
See the Readback Format section for more information.
Rev. D | Page 41 of 48
ADF7020
Data Sheet
REGISTER 8—POWER-DOWN TEST REGISTER
LOG AMP/
RSSI
CONTROL
BITS
DB10 DB9
DB1
DB2
DB0
DB7
PD4
DB13 DB12 DB11
DB8
PD5
DB6
PD3
DB5
PD2
DB4
PD1
DB3
SW1
LR2
LR1
PD6
C4(1) C3(0) C2(0) C1(0)
PD7
PD7 PA (Rx MODE)
PLE1
LOOP
PD2 PD1
(FROM REG 0)
CONDITION
0
1
PA OFF
PA ON
0
0
1
1
X
0
1
0
1
X
0
0
0
0
1
VCO/PLL OFF
PLL ON
VCO ON
PLL/VCO ON
PLL/VCO ON
SW1 Tx/Rx SWITCH
0
1
DEFAULT (ON)
OFF
PD3 LNA/MIXER ENABLE
LR2 LR1 RSSI MODE
0
1
LNA/MIXER OFF
LNA/MIXER ON
X
X
0
1
RSSI OFF
RSSI ON
PD6 DEMOD ENABLE
PD4 FILTER ENABLE
0
1
DEMOD OFF
DEMOD ON
0
1
FILTER OFF
FILTER ON
PD5 ADC ENABLE
0
1
ADC OFF
ADC ON
Figure 53. Register 8—Power-Down Test Register
Register 8—Power-Down Test Register Comments
•
•
For a combined LNA/PA matching network, Bit R8_DB12 should always be set to 0. This is the power-up default condition.
It is not necessary to write to this register under normal operating conditions.
Rev. D | Page 42 of 48
Data Sheet
ADF7020
REGISTER 9—AGC REGISTER
DIGITAL
TEST IQ
FILTER
GAIN
LNA
GAIN
ADDRESS
BITS
AGC HIGH THRESHOLD
AGC LOW THRESHOLD
FI1 FILTER CURRENT
GS1 AGC SEARCH
AGC LOW
GL7 GL6 GL5 GL4 GL3 GL2 GL1
THRESHOLD
0
1
LOW
HIGH
0
1
AUTO AGC
HOLD SETTING
0
0
0
0
.
0
0
0
0
.
0
0
0
0
.
0
0
0
0
.
0
0
0
1
.
0
1
1
0
.
1
0
1
0
.
1
2
3
4
.
.
.
78
79
80
FG2 FG1 FILTER GAIN
GC1 GAIN CONTROL
0
0
1
1
0
1
0
1
8
24
72
INVALID
0
1
AUTO
USER
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
1
1
0
0
0
0
0
1
1
1
0
1
1
0
1
1
0
0
1
0
AGC HIGH
GH7 GH6 GH5 GH4 GH3 GH2 GH1
THRESHOLD
0
0
0
0
.
.
.
1
1
1
0
0
0
0
.
.
.
0
0
0
0
0
0
0
.
.
.
0
0
1
0
0
0
0
.
.
.
1
1
0
0
0
0
1
.
.
.
1
1
0
0
1
1
0
.
.
.
1
1
0
1
0
1
0
.
.
.
0
1
0
1
2
3
4
.
.
.
78
79
80
LG2 LG1 LNA GAIN
0
0
1
1
0
1
0
1
<1
3
10
30
Figure 54. Register 9—AGC Register
Register 9—AGC Register Comments
•
This register does not need to be programmed in normal operation. Default AGC_Low_Threshold = 30, default
AGC_High_Threshold = 70. See the RSSI/AGC section for details. Default register setting = 0xB2 31E9.
•
•
AGC high and low settings must be more than 30 apart to ensure correct operation.
LNA gain of 30 is available only if LNA mode, R6_DB15, is set to 0.
Rev. D | Page 43 of 48
ADF7020
Data Sheet
REGISTER 10—AGC 2 REGISTER
I/Q PHASE
ADJUST
ADDRESS
BITS
I/Q GAIN ADJUST
AGC DELAY
LEAK FACTOR
PEAK RESPONSE
IF DB21 = 0, THEN GAIN
IS SELECTED.
IF DB21 = 1, THEN
DEFAULT = 0xA
ATTENUATE IS SELECTED
DEFAULT = 0xA
DEFAULT = 0x2
SIQ2 SELECT IQ
SIQ2 SELECT IQ
0
1
PHASE TO I CHANNEL
PHASE TO Q CHANNEL
0
1
GAIN TO I CHANNEL
GAIN TO Q CHANNEL
Figure 55. Register 10—AGC 2 Register
Register 10—AGC 2 Register Comments
•
•
This register is not used under normal operating conditions.
For ASK/OOK modulation, the recommended settings for operation over the full input range are peak response = 2, leak factor = 10
(default), and AGC delay =10 (default). Bit DB31 to Bit DB16 should be cleared. For bit-rates below 4kbps the AGC_Wait_time can
be increased by setting the AGC_Delay to 15. The SEQ_CLK should also be set at a minimum.
REGISTER 11—AFC REGISTER
CONTROL
BITS
AFC SCALING COEFFICIENT
INTERNAL
AE1 AFC
0
1
OFF
ON
Figure 56. Register 11—AFC Register
Register 11—AFC Register Comments
•
•
See the Internal AFC section to program the AFC scaling coefficient bits.
The AFC scaling coefficient bits can be programmed using the following formula:
AFC_Scaling_Coefficient = Round((500 × 224)/XTAL)
Rev. D | Page 44 of 48
Data Sheet
ADF7020
REGISTER 12—TEST REGISTER
ANALOG TEST
MUX
DIGITAL
TEST MODES
Σ-Δ
ADDRESS
BITS
TEST MODES
MANUAL FILTER CAL
PLL TEST MODES
P
PRESCALER
DEFAULT = 32. INCREASE
CR1 COUNTER RESET
NUMBER TO INCREASE BW
IF USER CAL ON
0
1
4/5 (DEFAULT)
8/9
0
1
DEFAULT
RESET
CS1 CAL SOURCE
0
1
INTERNAL
SERIAL IF BW CAL
Figure 57. Register 12—Test Register
Register 12—Test Register Comments
Programming the test register, Register 12, enables the test
DAC. In correlator mode, this can be done by writing to Digital
Test Mode 7 or 0x0001C00C.
This register does not need to be written to in normal
operation. The default test mode is 0x0000 000C, which puts
the part in normal operation.
To view the test DAC output when using the linear demodu-
lator, the user must remove a fixed offset term from the signal
using Register 13. This offset is nominally equal to the IF
frequency. The user can determine the value to program by
using the frequency error readback to determine the actual IF
and then programming half this value into the offset removal
field. It also has a signal gain term to allow the usage of the
maximum dynamic range of the DAC.
Using the Test DAC on the ADF7020 to Implement
Analog FM Demodulation and Measuring of SNR
The test DAC allows the output of the postdemodulator filter
for both the linear and correlator/demodulators (see Figure 30
and Figure 31) to be viewed externally. It takes the 16-bit filter
output and converts it to a high frequency, single-bit output
using a second-order Σ-Δ converter. The output can be viewed
on the CLKOUT pin. This signal, when filtered appropriately,
can then be used to
Setting Up the Test DAC
•
Digital test modes = 7: enables the test DAC, with no offset
removal (0x0001 C00C).
•
Monitor the signals at the FSK/ASK postdemodulator filter
output. This allows the demodulator output SNR to be
measured. Eye diagrams can also be constructed of the
received bit stream to measure the received signal quality.
•
Digital test modes = 10: enables the test DAC, with offset
removal (needed for linear demodulation only, 0x02 800C).
The output of the active demodulator drives the DAC, that is, if
the FSK correlator/demodulator is selected, the correlator filter
output drives the DAC.
•
Provide analog FM demodulation.
While the correlators and filters are clocked by DEMOD_CLK,
CDR_CLK clocks the test DAC. Note that although the test
DAC functions in a regular user mode, the best performance is
achieved when the CDR_CLK is increased up to or above the
frequency of DEMOD_CLK. The CDR block does not function
when this condition exists.
The evaluation boards for the ADF7020 contain land patterns
for placement of an RC filter on the CLKOUT line. This is
typically designed so that the cut-off frequency of the filter is
above the demodulated data rate.
Rev. D | Page 45 of 48
ADF7020
Data Sheet
REGISTER 13—OFFSET REMOVAL AND SIGNAL GAIN REGISTER
PULSE
EXTENSION
CONTROL
BITS
TEST DAC GAIN
TEST DAC OFFSET REMOVAL
KI
KP
KI DEFAULT = 3
KP DEFAULT = 2
PE4 PE3 PE2 PE1 PULSE EXTENSION
0
0
0
.
0
0
0
.
0
0
1
.
0
1
0
.
NORMAL PULSE WIDTH
2 × PULSE WIDTH
3 × PULSE WIDTH
.
.
.
.
.
.
.
.
.
.
.
1
1
1
1
16 × PULSE WIDTH
Figure 58. Register 13—Offset Removal and Signal Gain Register
Register 13—Offset Removal and Signal Gain Register Comments
•
Because the linear demodulator’s output is proportional to frequency, it usually consists of an offset combined with a relatively low
signal. The offset can be removed, up to a maximum of 1.0, and gained to use the full dynamic range of the DAC:
DAC_Input = (2Test_DAC_Gain) × (Signal − Test_DAC_Offset_Removal/4096)
•
Ki (default) = 3. Kp (default) = 2.
Rev. D | Page 46 of 48
Data Sheet
ADF7020
OUTLINE DIMENSIONS
7.00
BSC SQ
0.30
0.23
0.18
PIN 1
INDICATOR
PIN 1
INDICATOR
48
37
36
1
0.50
BSC
EXPOSED
PAD
4.25
4.10 SQ
3.95
12
13
25
24
0.45
0.40
0.35
0.20 MIN
TOP VIEW
BOTTOM VIEW
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
0.80
0.75
0.70
0.05 MAX
0.02 NOM
SECTION OF THIS DATA SHEET.
COPLANARITY
0.08
0.20 REF
SEATING
PLANE
COMPLIANT TO JEDEC STANDARDS MO-220-WKKD.
Figure 59. 48-Lead Lead Frame Chip Scale Package [LFCSP_WQ]
7 mm × 7 mm Body, Very Very Thin Quad
(CP-48-5)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
Temperature Range
Package Description
Package Option2
CP-48-5
ADF7020BCPZ
−40°C to +85°C
−40°C to +85°C
48-Lead Lead Frame Chip Scale Package [LFCSP_WQ]
48-Lead Lead Frame Chip Scale Package [LFCSP_WQ]
Control Mother Board
ADF7020BCPZ-RL
EVAL-ADF70xxMBZ
EVAL-ADF70xxMBZ2
EVAL-ADF7020DBZ1
EVAL-ADF7020DBZ2
EVAL-ADF7020DBZ3
CP-48-5
Evaluation Platform
902 MHz to 928 MHz Daughter Board
860 MHz to 870 MHz Daughter Board
430 MHz to 445 MHz Daughter Board
1 Z = RoHS Compliant Part.
2 Formerly CP-48-3 package.
Rev. D | Page 47 of 48
ADF7020
NOTES
Data Sheet
©2005–2012 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D05351-0-8/12(D)
Rev. D | Page 48 of 48
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