MAX9700AEUB+ [MAXIM]
1.2W, Low-EMI, Filterless, Class D Audio Amplifier;
| 型号： | MAX9700AEUB+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 1.2W, Low-EMI, Filterless, Class D Audio Amplifier 放大器 信息通信管理 光电二极管 商用集成电路 |
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
General Description
Features
● Filterless Amplifier Passes FCC Radiated
The MAX9700 mono class D audio power amplifier
provides class AB amplifier performance with class D
efficiency, conserving board space and extending battery
life. Using a class D architecture, the MAX9700
delivers 1.2W into an 8Ω load while offering efficiencies
above 90%. A low-EMI modulation scheme renders the
traditional class D output filter unnecessary.
Emissions Standards with 100mm of Cable
● Unique Spread-Spectrum Mode Offers 5dB
Emissions Improvement Over Conventional Methods
● Optional External SYNC Input
● Simple Master-Slave Setup for Stereo Operation
● 94% Efficiency
The MAX9700 offers two modulation schemes: a fixed-
frequency (FFM) mode, and a spread-spectrum (SSM)
mode that reduces EMI-radiated emissions due to the
modulation frequency. Furthermore, the MAX9700 oscillator
can be synchronized to an external clock through the
SYNC input, allowing the switching frequency to be user
defined. The SYNC input also allows multiple MAX9700s
to be cascaded and frequency locked, minimizing
interference due to clock intermodulation. The device
utilizes a fully differential architecture, a full-bridged
output, and comprehensive click-and-pop suppression.
The gain of the MAX9700 is set internally (MAX9700A:
6dB, MAX9700B: 12dB, MAX9700C: 15.6dB, MAX9700D:
20dB), further reducing external component count.
● 1.2W into 8Ω
● Low 0.01% THD+N
● High PSRR (72dB at 217Hz)
● Integrated Click-and-Pop Suppression
● Low Quiescent Current (4mA)
● Low-Power Shutdown Mode (0.1μA)
● Short-Circuit and Thermal-Overload Protection
● Available in Thermally Efficient, Space-Saving
Packages
• 10-Pin TDFN (3mm x 3mm x 0.8mm)
• 10-Pin μMAX
• 12-Bump UCSP (1.5mm x 2mm x 0.6mm)
Ordering Information
The MAX9700 features high 72dB PSRR, a low 0.01%
THD+N, and SNR in excess of 90dB. Short-circuit and
thermal-overload protection prevent the device from
damage during a fault condition. The MAX9700 is available
PIN-
PACKAGE
TOP
MARK
PART
TEMP RANGE
MAX9700AETB+
MAX9700AEUB+
-40°C to +85°C 10 TDFN-EP* ACM
-40°C to +85°C 10 µMAX
—
—
®
in 10-pin TDFN (3mm x 3mm x 0.8mm), 10-pin μMAX ,
MAX9700AEBC+T -40°C to +85°C 12 UCSP
and 12-bump UCSP™ (1.5mm x 2mm x 0.6mm) packages.
The MAX9700 is specified over the extended -40°C to
+85°C temperature range.
MAX9700BETB+
MAX9700BEUB+
-40°C to +85°C 10 TDFN-EP*
-40°C to +85°C 10 µMAX
ACI
—
MAX9700BEBC+T -40°C to +85°C 12 UCSP
—
Applications
*EP = Exposed pad.
Ordering Information continued and Selector Guide appears
at end of data sheet.
● Cellular Phones
● PDAs
● MP3 Players
● Portable Audio
Block Diagram
Pin Configurations
V
DD
TOP VIEW
V
1
2
3
4
5
10 PV
DD
DD
IN+
IN-
9
8
7
6
OUT-
DIFFERENTIAL
AUDIO INPUT
MODULATOR
AND H-BRIDGE
MAXꢀ700
OUT+
PGND
SYNC
GND
SHDN
SYNC
INPUT
OSCILLATOR
MAXꢀ700
TDFN/µMAX
Pin Configurations continued at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
μMAX is a registered trademark of Maxim Integrated Products, Inc.
19-3030; Rev 3; 3/18
MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Absolute Maximum Ratings
V
to GND ............................................................................6V
Continuous Power Dissipation (T = +70°C)
DD
A
PV
to PGND........................................................................6V
10-Pin TDFN (derate 24.4mW/°C above +70°C) ...1951.2mW
DD
GND to PGND......................................................-0.3V to +0.3V
All Other Pins to GND.............................. -0.3V to (V + 0.3V)
10-Pin μMAX (derate 5.6mW/oC above +70°C) ......444.4mW
12-Bump UCSP (derate 6.1mW/°C above +70°C)......484mW
Junction Temperature......................................................+150°C
Operating Temperature Range........................... -40°C to +85°C
Storage Temperature Range............................ -65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Bump Temperature (soldering)
DD
Continuous Current Into/Out of PV /PGND/OUT_......±600mA
DD
Continuous Input Current (all other pins).........................±20mA
Duration of OUT_ Short Circuit to GND or PV .....Continuous
DD
Duration of Short Circuit Between OUT+ and OUT-....Continuous
Reflow..........................................................................+235°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Electrical Characteristics
(V
= PV
= V
= 3.3V, V
= V
= 0V, SYNC = GND (FFM), R = 8Ω, R connected between OUT+ and OUT-,
DD
DD
to T
SHDN
GND
PGND L L
T
= T
, unless otherwise noted. Typical values are at T = +25°C.) (Notes 1, 2)
MAX A
A
MIN
PARAMETER
SYMBOL
CONDITIONS
Inferred from PSRR test
MIN
TYP
MAX
UNITS
GENERAL
Supply Voltage Range
Quiescent Current
Shutdown Current
Turn-On Time
V
2.5
5.5
5.2
10
V
DD
I
4
0.1
30
mA
µA
ms
kΩ
V
DD
I
SHDN
t
ON
Input Resistance
Input Bias Voltage
R
T
= +25°C
A
12
20
IN
V
Either input
MAX9700A
MAX9700B
MAX9700C
MAX9700D
0.73
0.83
6
0.93
BIAS
12
Voltage Gain
A
dB
V
15.6
20
T
T
= +25°C
±11
±80
A
Output Offset Voltage
V
mV
dB
OS
≤ T ≤ T
MAX
±120
MIN
A
Common-Mode Rejection Ratio
CMRR
PSRR
f
= 1kHz, input referred
72
70
IN
V
= 2.5V to 5.5V, T = +25°C
50
DD
A
Power-Supply Rejection Ratio
(Note 3)
f
f
= 217Hz
= 20kHz
72
dB
RIPPLE
RIPPLE
200mV
ripple
P-P
55
R = 8Ω
450
800
L
Output Power
P
THD+N = 1%
mW
OUT
R = 6Ω
L
R = 8Ω,
P = 125mW
OUT
L
0.01
0.01
Total Harmonic Distortion
Plus Noise
f
= 1kHz, either
IN
THD+N
%
FFM or SSM
R = 6Ω,
L
P
= 125mW
OUT
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Electrical Characteristics (continued)
(V
= PV
= V
= 3.3V, V
= V
= 0V, SYNC = GND (FFM), R = 8Ω, R connected between OUT+ and OUT-,
DD
DD
SHDN
GND
PGND L L
T
= T
to T
, unless otherwise noted. Typical values are at T = +25°C.) (Notes 1, 2)
MAX A
A
MIN
PARAMETER
SYMBOL
CONDITIONS
BW = 22Hz
MIN
TYP
89
MAX
UNITS
FFM
SSM
FFM
SSM
to 22kHz
87
Signal-to-Noise Ratio
Oscillator Frequency
SNR
V
= 2V
dB
OUT
RMS
92
A-weighted
90
SYNC = GND
980
1100
1450
1220
1620
SYNC = unconnected
1280
f
kHz
OSC
1220
±120
SYNC = V
(SSM mode)
DD
SYNC Frequency Lock Range
Efficiency
800
2
2000
kHz
%
η
P
= 500mW, f = 1kHz
94
OUT
IN
DIGITAL INPUTS (SHDN, SYNC)
V
V
IH
IL
Input Thresholds
V
0.8
±1
±5
SHDN Input Leakage Current
SYNC Input Current
µA
µA
Electrical Characteristics
(V
= PV
= V
= 5V, V
= V
= 0V, SYNC = GND (FFM), R = 8Ω, R connected between OUT+ and OUT-, T = T
DD
DD
SHDN
GND
PGND L L A MIN
to T
, unless otherwise noted. Typical values are at T = +25°C.) (Notes 1, 2)
A
MAX
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
5.2
MAX
UNITS
Quiescent Current
I
mA
µA
dB
DD
Shutdown Current
I
0.1
SHDN
Common-Mode Rejection Ratio
CMRR
f = 1kHz, input referred
72
f = 217Hz
f = 20kHz
72
Power-Supply Rejection Ratio
Output Power
PSRR
200mV
ripple
dB
mW
%
P-P
55
R = 16Ω
700
1200
1600
0.015
0.02
92.5
90.5
95.5
93.5
L
P
THD+N = 1%
R = 8Ω
L
OUT
R = 6Ω
L
R = 8Ω, P
= 125mW
Total Harmonic Distortion
Plus Noise
f = 1kHz, either
FFM or SSM
L
OUT
THD+N
SNR
R = 4Ω, P
= 125mW
L
OUT
FFM
SSM
FFM
SSM
BW = 22Hz to
22kHz
V
=
OUT
Signal-to-Noise Ratio
dB
3V
RMS
A-weighted
Note 1: All devices are 100% production tested at T = +25°C. All temperature limits are guaranteed by design.
A
Note 2: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For R = 4Ω, L = 33μH.
L
For R = 8Ω, L = 68μH. For R = 16Ω, L = 136μH.
L
L
Note 3: PSRR is specified with the amplifier inputs connected to GND through C
.
IN
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Typical Operating Characteristics
(V
= 3.3V, SYNC = GND (SSM), T = +25°C, unless otherwise noted.)
A
DD
TOTAL HARMONIC DISTORTION PLUS NOISE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
vs. FREQUENCY
1
1
0.1
1
V
DD
= +3.3V
V
DD
= +5V
V
= +3.3V
DD
R = 8Ω
R
L
= 8Ω
R = 8Ω
L
L
P
= 125mW
OUT
0.1
0.1
0.01
P
OUT
= 300mW
P
OUT
= 300mW
SSM MODE
0.01
0.01
0.001
P
OUT
= 125mW
P
= 125mW
10k
OUT
FFM MODE
0.001
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
FREQUENCY (Hz)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
100
10
1
100
100
V
= 5V
V
= 5V
DD
DD
V
= 5V
DD
R = 16Ω
R = 4Ω
L
L
R = 8Ω
L
10
10
1
1
f = 1kHz
f = 100Hz
f = 100Hz
0.1
0.01
f = 10kHz
0.1
0.01
0.1
f = 10kHz
0.01
f = 10kHz
1.5
f = 1kHz
0.5 1.0 1.5 2.0
f = 100Hz
0.6 0.8
f = 1kHz
0.4
0.001
0.001
0.001
0
0.2
1.0
2.5 3.0 3.5
0
0.5
1.0
2.0
0
OUTPUT POWER (W)
OUTPUT POWER (W)
OUTPUT POWER (W)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
100
100
100
10
1
V
= 2.5V
V
= 5V
V
= 5V
DD
DD
DD
R = 8Ω
f = 1kHz
R = 8Ω
f = 1kHz
R = 8Ω
L
V
= 1.25V
10
10
CM
L
L
NO INPUT CAPACITORS
FFM
(SYNC = GND)
f
= 1.4MHz
SYNC
1
1
f
= 800kHz
SYNC
DIFFERENTIAL
INPUT
SSM
0.1
0.01
0.1
0.01
0.1
0.01
SINGLE ENDED
FFM
(SYNC UNCONNECTED)
f
= 2MHz
SYNC
0.001
0.001
0.001
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
2.0
0
0.1
0.2
0.3
0.4
0.5
OUTPUT POWER (W)
OUTPUT POWER (W)
OUTPUT POWER (W)
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Typical Operating Characteristics (continued)
(V
= 3.3V, SYNC = GND (SSM), T = +25°C, unless otherwise noted.)
A
DD
TOTAL HARMONIC DISTORTION PLUS NOISE
EFFICIENCY vs. OUTPUT POWER
EFFICIENCY vs. OUTPUT POWER
vs. COMMON-MODE VOLTAGE
10
100
90
80
70
60
50
40
30
20
10
0
100
V
= 3.3V
DD
90
80
R = 8Ω
f = 1kHz
L
R = 8Ω
L
P
= 300mW
OUT
70
DIFFERENTIAL INPUT
R = 8Ω
L
R = 4Ω
L
1
R = 4Ω
L
60
50
40
30
20
10
0
0.1
V
DD
= 3.3V
V
DD
= 5V
f = 1kHz
f = 1kHz
0.01
0
0.5
1.0
1.5
2.0
2.5
3.0
1.0
0
0.3
0.6
0.9
1.2
1.5
0
0.5
1.5
2.0
2.5
3.0
COMMON-MODE VOLTAGE (V)
OUTPUT POWER (W)
OUTPUT POWER (W)
EFFICIENCY
vs. SYNC INPUT FREQUENCY
OUTPUT POWER vs.
SUPPLY VOLTAGE
EFFICIENCY vs. SUPPLY VOLTAGE
3.5
3.0
2.5
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
f = 1kHz
R = 4Ω
L
THD+N = 10%
THD+N = 1%
R = 8Ω
R = 4Ω
L
R = 8Ω
L
R = 4Ω
L
L
2.0
1.5
1.0
0.5
0
THD+N = 10%
V
= 3.3V
DD
f = 1kHz
= 300mW
P
OUT
R = 8Ω
THD+N = 1%
L
f = 1kHz
= MAX (THD+N = 1%)
R = 8Ω
L
P
OUT
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
800 1000 1200 1400 1600 1800 2000
SYNC FREQUENCY (kHz)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
OUTPUT POWER vs. LOAD RESISTANCE
2000
1600
1200
800
400
0
0
0
f = 1kHz
THD+N = 1%
INPUT REFERRED
OUTPUT REFERRED
INPUTS AC GROUNDED
-10
-20
-30
-40
-50
-60
-70
-80
-10
V
IN
= 200mV
P-P
-20
-30
-40
-50
-60
-70
-80
V
= 3.3V
DD
V
DD
= 5V
V
DD
= 3.3V
-90
-90
-100
-100
0
10 20 30 40 50 60 70 80 90 100
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
10k
100k
LOAD RESISTANCE (Ω)
FREQUENCY (Hz)
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Typical Operating Characteristics (continued)
(V
= 3.3V, SYNC = GND (SSM), T = +25°C, unless otherwise noted.)
A
DD
OUTPUT FREQUENCY SPECTRUM
GSM POWER-SUPPLY REJECTION
MAX9700 toc19
0
-20
FFM MODE
V
= -60dBV
OUT
f = 1kHz
500mV/div
V
DD
R = 8Ω
L
-40
UNWEIGHTED
-60
-80
-100
-120
-140
MAX9700
OUTPUT
100mV/div
0
5k
10k
FREQUENCY (Hz)
15k
20k
2ms/div
DUTY CYCLE = 88%
R = 8Ω
f = 217Hz
INPUT LOW = 3V
INPUT HIGH = 3.5V
L
WIDEBAND OUTPUT SPECTRUM
(FFM MODE)
OUTPUT FREQUENCY SPECTRUM
OUTPUT FREQUENCY SPECTRUM
0
0
0
-20
RBW = 10kHz
SSM MODE
SSM MODE
-10
-20
-30
-40
-50
-60
-70
-80
V
OUT
= -60dBV
V
OUT
= -60dBV
-20
-40
f = 1kHz
f = 1kHz
R = 8Ω
R = 8Ω
L
L
-40
UNWEIGHTED
A-WEIGHTED
-60
-60
-80
-80
-100
-120
-140
-100
-120
-140
-90
-100
1M
10M
100M
1G
0
5k
10k
FREQUENCY (Hz)
15k
20k
0
5k
10k
FREQUENCY (Hz)
15k
20k
FREQUENCY (Hz)
WIDEBAND OUTPUT SPECTRUM
(SSM MODE)
TURN-ON/TURN-OFF RESPONSE
0
RBW = 10kHz
-10
-20
-30
-40
-50
-60
-70
-80
3V
SHDN
0V
MAX9700
OUTPUT
250mV/div
-90
-100
1M
10M
100M
1G
10ms/div
f = 1kHz
R = 8Ω
FREQUENCY (Hz)
L
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Typical Operating Characteristics (continued)
(V
= 3.3V, SYNC = GND (SSM), T = +25°C, unless otherwise noted.)
A
DD
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
6.0
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
T
= +85°C
A
5.5
5.0
4.5
4.0
3.5
3.0
T
= +85°C
A
T
= +25°C
A
T
A
= +25°C
T
= -40°C
A
T
= -40°C
4.5
A
2.5
3.0
3.5
4.0
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Functional Diagram
V
DD
1µF
1
(A1)
10
(B4)
6
(A3)
V
PV
DD
SYNC
DD
5
(B2) SHDN
UVLO/POWER
MANAGEMENT
CLICK-AND-POP
SUPPRESSION
OSCILLATOR
PV
DD
2
(B1)
1µF
8
(A4)
IN+
IN-
OUT+
OUT-
PGND
CLASS D
MODULATOR
3
(C1)
1µF
PV
DD
9
(C4)
MAX9700
PGND
GND
PGND
7
4
(B3)
(C2)
( ) UCSP BUMP.
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Pin Description
PIN
BUMP
NAME
FUNCTION
TDFN/µMAX
UCSP
Analog Power Supply. Connect to an external power supply. Bypass to GND with a
1µF capacitor.
1
A1
V
DD
2
3
4
5
B1
C1
C2
B2
IN+
IN-
Noninverting Audio Input
Inverting Audio Input
Analog Ground
GND
SHDN
Active-Low Shutdown Input. Connect to V
for normal operation.
DD
Frequency Select and External Clock Input.
SYNC = GND: Fixed-frequency mode with f = 1100kHz.
S
6
A3
SYNC
SYNC = Unconnected: Fixed-frequency mode with f = 1450kHz.
S
SYNC = V : Spread-spectrum mode with f = 1220kH ±120kHz.
DD
S
SYNC = Clocked: Fixed-frequency mode with f = external clock frequency.
S
7
8
B3
A4
C4
B4
PGND
OUT+
OUT-
Power Ground
Amplifier-Output Positive Phase
Amplifier-Output Negative Phase
9
10
PV
H-Bridge Power Supply. Connect to V
.
DD
DD
Exposed Pad. Internallly connected to GND. Connect to a large ground plane to
maximize thermal performance. Not intended as an electrical connection point.
(TDFN package only.)
—
—
EP
Operating Modes
Detailed Description
The MAX9700 filterless, class D audio power amplifier
features several improvements to switch-mode amplifier
technology. The MAX9700 offers class AB performance
with class D efficiency, while occupying minimal board
space. A unique filterless modulation scheme, synchroniz-
able switching frequency, and SSM mode create a com-
pact, flexible, low-noise, efficient audio power amplifier.
The differential input architecture reduces common-mode
noise pickup, and can be used without input-coupling
capacitors. The device can also be configured as a single-
ended input amplifier.
Fixed-Frequency Modulation (FFM) Mode
The MAX9700 features two FFM modes. The FFM modes
are selected by setting SYNC = GND for a 1.1MHz switching
frequency, and SYNC = UNCONNECTED for a 1.45MHz
switching frequency. In FFM mode, the frequency spectrum
of the class D output consists of the fundamental switching
frequency and its associated harmonics (see the Wideband
FFT graph in the Typical Operating Characteristics). The
MAX9700 allows the switching frequency to be changed by
+32%, should the frequency of one or more of the harmon-
ics fall in a sensitive band. This can be done at any time
and does not affect audio reproduction.
Comparators monitor the MAX9700 inputs and compare
the complementary input voltages to the sawtooth wave-
form. The comparators trip when the input magnitude of
the sawtooth exceeds their corresponding input voltage.
Both comparators reset at a fixed time after the rising
edge of the second comparator trip point, generating a
Spread-Spectrum Modulation (SSM) Mode
The MAX9700 features a unique spread-spectrum
mode that flattens the wideband spectral components,
improving EMI emissions that may be radiated by the
speaker and cables by 5dB. Proprietary techniques
ensure that the cycle-to-cycle variation of the switch-
ing period does not degrade audio reproduction or effi-
ciency (see the Typical Operating Characteristics). Select
minimum-width pulse t
at the output of the sec-
ON(MIN)
ond comparator (Figure 1). As the input voltage increases
or decreases, the duration of the pulse at one output
increases (the first comparator to trip) while the other
SSM mode by setting SYNC = V . In SSM mode,
DD
output pulse duration remains at t
. This causes
ON(MIN)
the switching frequency varies randomly by ±120kHz
around the center frequency (1.22MHz). The modulation
scheme remains the same, but the period of the saw-
the net voltage across the speaker (V
- V ) to
OUT-
OUT+
change.
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
t
SW
V
IN-
V
IN+
OUT-
OUT+
t
ON(MIN)
V
OUT+
- V
OUT-
Figure 1. MAX9700 Outputs with an Input Signal Applied
External Clock Mode
Table 1. Operating Modes
The SYNC input allows the MAX9700 to be synchronized
to a system clock (allowing a fully synchronous system),
or allocating the spectral components of the switching
harmonics to insensitive frequency bands. Applying an
external TTL clock of 800kHz to 2MHz to SYNC syn-
chronizes the switching frequency of the MAX9700. The
period of the SYNC clock can be randomized, enabling
the MAX9700 to be synchronized to another MAX9700
operating in SSM mode.
SYNC INPUT
MODE
FFM with f = 1100kHz
GND
S
UNCONNECTED FFM with f = 1450kHz
S
V
SSM with f = 1220kHz ±120kHz
S
DD
Clocked
FFM with f = external clock frequency
S
tooth waveform changes from cycle to cycle (Figure 2).
Instead of a large amount of spectral energy present at
multiples of the switching frequency, the energy is now
spread over a bandwidth that increases with frequency.
Above a few megahertz, the wideband spectrum looks
like white noise for EMI purposes (Figure 3).
Filterless Modulation/Common-Mode Idle
The MAX9700 uses Maxim’s modulation scheme that
eliminates the LC filter required by traditional class
D amplifiers, improving efficiency, reducing component
count, and conserving board space and system cost.
Conventional class D amplifiers output a 50% duty cycle
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
t
t
t
t
SW
SW
SW
SW
V
IN-
V
IN+
OUT-
OUT+
t
ON(MIN)
V
OUT+
- V
OUT-
Figure 2. MAX9700 Output with an Input Signal Applied (SSM Mode)
square wave when no signal is present. With no filter,
the square wave appears across the load as a DC volt-
age, resulting in finite load current, increasing power
consumption. When no signal is present at the input of
the MAX9700, the outputs switch as shown in Figure 4.
Because the MAX9700 drives the speaker differentially,
the two outputs cancel each other, resulting in no net Idle
Mode™ voltage across the speaker, minimizing power
consumption.
amplifier, the output transistors act as current-steering
switches and consume negligible additional power. Any
power loss associated with the class D output stage is
mostly due to the I x R loss of the MOSFET on-resistance,
and quiescent current overhead.
The theoretical best efficiency of a linear amplifier is 78%;
however, that efficiency is only exhibited at peak output
powers. Under normal operating levels (typical music
reproduction levels), efficiency falls below 30%, whereas
the MAX9700 still exhibits >90% efficiencies under the
same conditions (Figure 5).
Efficiency
Efficiency of a class D amplifier is attributed to the region
of operation of the output stage transistors. In a class D
Idle Mode is a trademark of Maxim Integrated Products
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
V
= 0V
IN
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
OUT-
OUT+
30.0
60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0
FREQUENCY (MHz)
V
- V = 0V
OUT+ OUT-
Figure 3. MAX9700 EMI Spectrum
Figure 4. MAX9700 Outputs with No Input Signal
Shutdown
The MAX9700 has a shutdown mode that reduces power
consumption and extends battery life. Driving SHDN low
places the MAX9700 in a low-power (0.1μA) shutdown
EFFICIENCY vs. OUTPUT POWER
100
90
80
mode. Connect SHDN to V
for normal operation.
DD
Click-and-Pop Suppression
MAX9700
70
60
50
40
30
20
10
0
The MAX9700 features comprehensive click-and-pop
suppression that eliminates audible transients on startup
and shutdown. While in shutdown, the H-bridge is in a
high-impedance state. During startup or power-up, the
input amplifiers are muted and an internal loop sets the
modulator bias voltages to the correct levels, prevent-
ing clicks and pops when the H-bridge is subsequently
enabled. For 35ms following startup, a soft-start function
gradually unmutes the input amplifiers.
CLASS AB
V
= 3.3V
DD
f = 1kHz
R - 8Ω
L
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7
OUTPUT POWER (W)
Applications Information
Figure 5. MAX9700 Efficiency vs. Class AB Efficiency
Filterless Operation
Traditional class D amplifiers require an output filter to
recover the audio signal from the amplifier’s output. The
filters add cost, increase the solution size of the ampli-
fier, and can decrease efficiency. The traditional PWM
Because the frequency of the MAX9700 output is well
beyond the bandwidth of most speakers, voice coil move-
ment due to the square-wave frequency is very small.
Although this movement is small, a speaker not designed
to handle the additional power can be damaged. For
optimum results, use a speaker with a series inductance
>10μH. Typical 8Ω speakers exhibit series inductances in
the 20μH to 100μH range.
scheme uses large differential output swings (2 x V
DD
peak-to-peak) and causes large ripple currents. Any para-
sitic resistance in the filter components results in a loss of
power, lowering the efficiency.
The MAX9700 does not require an output filter. The
device relies on the inherent inductance of the speaker
coil and the natural filtering of both the speaker and
the human ear to recover the audio component of the
square-wave output. Eliminating the output filter results in
a smaller, less costly, more efficient solution.
Power-Conversion Efficiency
Unlike a class AB amplifier, the output offset voltage of a
class D amplifier does not noticeably increase quiescent
current draw when a load is applied. This is due to the
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
power conversion of the class D amplifier. For example,
an 8mV DC offset across an 8Ω load results in 1mA extra
current consumption in a class AB device. In the class
D case, an 8mV offset into 8Ω equates to an additional
power drain of 8μW. Due to the high efficiency of the
class D amplifier, this represents an additional quiescent-
1µF
SINGLE-ENDED
AUDIO INPUT
IN+
IN-
MAX9700
current draw of 8μW/(V /100η), which is on the order of
DD
1µF
a few microamps.
Input Amplifier
Differential Input
Figure 6. Single-Ended Input
The MAX9700 features a differential input structure,
making it compatible with many CODECs, and offering
improved noise immunity over a single-ended input ampli-
fier. In devices such as cellular phones, high-frequency
signals from the RF transmitter can be picked up by the
amplifier’s input traces. The signals appear at the ampli-
fier’s inputs as common-mode noise. A differential input
amplifier amplifies the difference of the two inputs; any
signal common to both inputs is canceled.
whose dielectrics have low-voltage coefficients, such as
tantalum or aluminum electrolytic. Capacitors with high-
voltage coefficients, such as ceramics, may result in
increased distortion at low frequencies.
Other considerations when designing the input filter
include the constraints of the overall system and the
actual frequency band of interest. Although high-fidelity
audio calls for a flat gain response between 20Hz and
20kHz, portable voice-reproduction devices such as cellu-
lar phones and two-way radios need only concentrate on
the frequency range of the spoken human voice (typically
300Hz to 3.5kHz). In addition, speakers used in portable
devices typically have a poor response below 150Hz.
Taking these two factors into consideration, the input
filter may not need to be designed for a 20Hz to 20kHz
response, saving both board space and cost due to the
use of smaller capacitors.
Single-Ended Input
The MAX9700 can be configured as a single-ended input
amplifier by capacitively coupling either input to GND and
driving the other input (Figure 6).
DC-Coupled Input
The input amplifier can accept DC-coupled inputs that
are biased within the amplifier’s common-mode range
(see the Typical Operating Characteristics). DC coupling
eliminates the input-coupling capacitors, reducing compo-
nent count to potentially one external component (see the
System Diagram). However, the low-frequency rejection
of the capacitors is lost, allowing low-frequency signals to
feedthrough to the load.
Output Filter
The MAX9700 does not require an output filter. The
device passes FCC emissions standards with 100mm
of unshielded speaker cables. However, output filter-
ing can be used if a design is failing radiated emissions
due to board layout or cable length, or the circuit is near
EMI-sensitive devices. Use an LC filter when radiated
emissions are a concern, or when long leads are used to
connect the amplifier to the speaker.
Component Selection
Input Filter
An input capacitor, C , in conjunction with the input
IN
impedance of the MAX9700 forms a highpass filter that
removes the DC bias from an incoming signal. The
AC-coupling capacitor allows the amplifier to bias the sig-
nal to an optimum DC level. Assuming zero source imped-
ance, the -3dB point of the highpass filter is given by:
Supply Bypassing/Layout
Proper power-supply bypassing ensures low-distortion
operation. For optimum performance, bypass V
to
DD
GND and PV
to PGND with separate 0.1μF capacitors
DD
as close to each pin as possible. A low-impedance, high-
current power-supply connection to PV is assumed.
1
f
=
−3dB
DD
2πR C
IN IN
Additional bulk capacitance should be added as required
depending on the application and power-supply charac-
teristics. GND and PGND should be star connected to
system ground. Refer to the MAX9700 evaluation kit for
layout guidance.
Choose C
so f
is well below the lowest fre-
-3dB
IN
quency of interest. Setting f
too high affects the
-3dB
low-frequency response of the amplifier. Use capacitors
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Stereo Configuration
Two MAX9700s can be configured as a stereo amplifier
(Figure 7). Device U1 is the master amplifier; its unfil-
tered output drives the SYNC input of the slave device
(U2), synchronizing the switching frequencies of the two
devices. Synchronizing two MAX9700s ensures that no
beat frequencies occur within the audio spectrum. This
configuration works when the master device is in either
FFM or SSM mode. There is excellent THD+N perfor-
mance and minimal crosstalk between devices due to
the SYNC connection (Figures 8 and 9). U2 locks onto
only the frequency present at SYNC, not the pulse width.
The internal feedback loop of device U2 ensures that the
audio component of U1’s output is rejected.
V
DD
1µF
V
DD
PV
DD
MAX9700
IN+
IN-
OUT+
RIGHT-CHANNEL
DIFFERENTIAL
AUDIO INPUT
OUT-
SYNC
Designing with Volume Control
The MAX9700 can easily be driven by single-ended
sources (Figure 6), but extra care is needed if the source
impedance “seen” by each differential input is unbalanced,
such as the case in Figure 10a, where the MAX9700 is
used with an audio taper potentiometer acting as a vol-
ume control. Functionally, this configuration works well,
but can suffer from click-pop transients at power-up (or
coming out of SHDN) depending on the volume-control
setting. As shown, the click-pop performance is fine for
either max or min volume, but worsens at other settings.
1µF
V
DD
PV
DD
MAX9700
IN+
IN-
OUT+
LEFT-CHANNEL
DIFFERENTIAL
AUDIO INPUT
OUT-
SYNC
Figure 7. Master-Slave Stereo Configuration
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
CROSSTALK vs. FREQUENCY
0
100
10
1
V
= 3.3V
DD
V
= 3.3V
DD
R = 8Ω
f = 1kHz
L
-20
-40
f = 1kHz
R = 8Ω
SLAVE DEVICE
L
V
= 500mV
IN
P-P
-60
MASTER-TO-SLAVE
SLAVE-TO-MASTER
0.1
-80
-100
-120
0.01
0.001
10
100
1k
10k
100k
0
0.1
0.2
0.3
0.4
0.5
FREQUENCY (Hz)
OUTPUT POWER (W)
Figure 8. Master-Slave THD+N
Figure 9. Master-Slave Crosstalk
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
One solution is the configuration shown in Figure 10b.
The potentiometer is connected between the differential
inputs, and these “see” identical RC paths when the
device powers up. The variable resistive element appears
between the two inputs, meaning the setting affects both
inputs the same way. The potentiometer is audio taper,
as in Figure 10a. This significantly improves transient
performance on power-up or release from SHDN. A simi-
lar approach can be applied when the MAX9700 is driven
differentially and a volume control is required.
UCSP Applications Information
For the latest application details on UCSP construc-
tion, dimensions, tape carrier information, PC board
techniques, bump-pad layout, and recommended reflow
temperature profile, as well as the latest information on
reliability testing results, refer to the Application Note:
UCSP—A Wafer-Level Chip-Scale Package available on
Maxim’s website at www.maximintegrated.com/ucsp.
1µF
22kΩ
CW
1µF
IN-
IN-
50kΩ
CW
MAX9700
50kΩ
MAX9700
1µF
IN+
22kΩ
IN+
1µF
Figure 10b. Improved Single-Ended Drive of MAX9700 Plus
Volume
Figure 10a. Single-Ended Drive of MAX9700 Plus Volume
Ordering Information (continued)
Selector Guide
PART
PIN-PACKAGE
10 TDFN-EP*
10 µMAX
GAIN (dB)
PIN-
PACKAGE
TOP
PART
TEMP RANGE
MARK
ACN
—
MAX9700AETB+
MAX9700AEUB+
MAX9700AEBC+T
MAX9700BETB+
MAX9700BEUB+
MAX9700BEBC+T
MAX9700CETB+
MAX9700CEUB+
MAX9700CEBC+T
MAX9700DETB+
MAX9700DEUB+
MAX9700DEBC+T
6
6
MAX9700CETB+
MAX9700CEUB+
-40°C to +85°C 10 TDFN-EP*
-40°C to +85°C 10 µMAX
12 UCSP
6
MAX9700CEBC+T -40°C to +85°C 12 UCSP
—
10 TDFN-EP*
10 µMAX
12
MAX9700DETB+
MAX9700DEUB+
-40°C to +85°C 10 TDFN-EP* ACO
12
-40°C to +85°C 10 µMAX
—
—
12 UCSP
12
MAX9700DEBC+T -40°C to +85°C 12 UCSP
10 TDFN-EP*
10 µMAX
15.6
15.6
15.6
20
*EP = Exposed pad.
12 UCSP
10 TDFN-EP*
10 µMAX
20
12 UCSP
20
*EP = Exposed pad.
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
System Diagram
V
DD
1µF
V
DD
V
0.1µF
PV
DD
DD
AUX_IN
BIAS
OUT+
IN+
MAX9700
IN-
OUT-
OUT
2.2kΩ
SHDN
SYNC
CODEC/
BASEBAND
PROCESSOR
OUT
MAXꢀ0ꢁꢂ
2.2kΩ
0.1µF
IN+
IN-
V
DD
0.1µF
1µF
V
DD
SHDN
1µF
1µF
INL
OUTL
OUTR
MAX9722
INR
µCONTROLLER
PV
SV
SS
SS
C1P
CIN
1µF
1µF
Chip Information
TRANSISTOR COUNT: 3595
Pin Configurations (continued)
TOP VIEW
(BUMP SIDE DOWN)
1
PROCESS: BiCMOS
MAX9700
2
3
4
V
SYNC
PGND
OUT+
DD
A
B
IN+
IN-
SHDN
PV
DD
GND
OUT-
C
ꢀCꢁꢂ
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE TYPE
12 UCSP
PACKAGE CODE
B12-11
DOCUMENT NO.
21-0104
10 TDFN-EP
10 μMAX
T1033-1
21-0137
U10-2
21-0061
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MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Revision History
REVISION REVISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
10/03
6/04
0
1
2
3
Initial release
—
Changes made to TOCs and specs
3–8, 14, 15
1, 2, 3, 8, 14
1, 14
10/08
3/18
Addition of EP information to pin description table
Updated Ordering Information
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
©
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
2018 Maxim Integrated Products, Inc.
│ 17
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