MAXIM MAX9700AEUB

19-3030; Rev 2; 10/08
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
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 patented, low-EMI modulation scheme renders
the traditional class D output filter unnecessary.
The MAX9700 offers two modulation schemes: a fixedfrequency (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 fullbridged 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.
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 in 10-pin TDFN (3mm ✕ 3mm ✕ 0.8mm), 10-pin
µMAX®, and 12-bump UCSP™ (1.5mm ✕ 2mm ✕ 0.6mm)
packages. The MAX9700 is specified over the extended
-40°C to +85°C temperature range.
Applications
Cellular Phones
MP3 Players
PDAs
Portable Audio
Block Diagram
Features
♦ Filterless Amplifier Passes FCC Radiated
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
♦ 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
TEMP RANGE
PINPACKAGE
MAX9700AETB
-40oC to +85oC
10 TDFN-EP*
MAX9700AEUB
-40oC to +85oC
10 µMAX
PART
o
o
TOP
MARK
ACM
—
MAX9700AEBC-T
-40 C to +85 C
12 UCSP
MAX9700BETB
-40oC to +85oC
10 TDFN-EP*
MAX9700BEUB
-40oC to +85oC
10 µMAX
—
12 UCSP
—
o
MAX9700BEBC-T
o
-40 C to +85 C
—
ACI
*EP = Exposed pad.
Ordering Information continued and Selector Guide appears
at end of data sheet.
VDD
Pin Configurations
DIFFERENTIAL
AUDIO INPUT
SYNC
INPUT
MODULATOR
AND H-BRIDGE
OSCILLATOR
MAX9700
TOP VIEW
VDD 1
IN+
2
IN-
3
GND
SHDN
10 PVDD
9
OUT-
8
OUT+
4
7
PGND
5
6
SYNC
MAX9700
TDFN/μMAX
UCSP is a trademark of Maxim Integrated Products, Inc.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX9700
General Description
MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
ABSOLUTE MAXIMUM RATINGS
VDD to GND..............................................................................6V
PVDD to PGND .........................................................................6V
GND to PGND .......................................................-0.3V to +0.3V
All Other Pins to GND.................................-0.3V to (VDD + 0.3V)
Continuous Current Into/Out of PVDD/PGND/OUT_........±600mA
Continuous Input Current (all other pins) .........................±20mA
Duration of OUT_ Short Circuit to GND or PVDD ........Continuous
Duration of Short Circuit Between OUT+ and OUT- ..Continuous
Continuous Power Dissipation (TA = +70°C)
10-Pin TDFN (derate 24.4mW/°C above +70°C) .....1951.2mW
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)
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
(VDD = PVDD = V SHDN = 3.3V, VGND = VPGND = 0V, SYNC = GND (FFM), RL = 8Ω, RL connected between OUT+ and OUT-,
TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
GENERAL
Supply Voltage Range
VDD
5.5
V
Quiescent Current
IDD
Inferred from PSRR test
2.5
4
5.2
mA
Shutdown Current
ISHDN
0.1
10
µA
Turn-On Time
tON
Input Resistance
RIN
TA = +25°C
12
20
VBIAS
Either input
0.73
0.83
Input Bias Voltage
Voltage Gain
Output Offset Voltage
Common-Mode Rejection Ratio
Power-Supply Rejection Ratio
(Note 3)
Output Power
Total Harmonic Distortion
Plus Noise
2
AV
VOS
CMRR
30
MAX9700A
6
MAX9700B
12
MAX9700C
15.6
MAX9700D
20
TA = +25°C
±11
TMIN ≤ TA ≤ TMAX
fIN = 1kHz, input referred
POUT
THD+N
200mVP-P ripple
THD+N = 1%
fIN = 1kHz, either
FFM or SSM
kΩ
0.93
72
50
V
dB
±80
±120
VDD = 2.5V to 5.5V, TA = +25°C
PSRR
ms
mV
dB
70
fRIPPLE = 217Hz
72
fRIPPLE = 20kHz
55
RL = 8Ω
450
RL = 6Ω
800
RL = 8Ω,
POUT = 125mW
0.01
RL = 6Ω,
POUT = 125mW
0.01
dB
mW
%
_______________________________________________________________________________________
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
(VDD = PVDD = V SHDN = 3.3V, VGND = VPGND = 0V, SYNC = GND (FFM), RL = 8Ω, RL connected between OUT+ and OUT-,
TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
BW = 22Hz
to 22kHz
Signal-to-Noise Ratio
SNR
VOUT = 2VRMS
A-weighted
Oscillator Frequency
fOSC
FFM
89
SSM
87
FFM
92
SSM
UNITS
dB
90
980
1100
1220
SYNC = unconnected
1280
1450
1620
kHz
1220
±120
SYNC Frequency Lock Range
800
η
MAX
SYNC = GND
SYNC = VDD (SSM mode)
Efficiency
TYP
POUT = 500mW, fIN = 1kHz
2000
94
kHz
%
DIGITAL INPUTS (SHDN, SYNC)
VIH
Input Thresholds
2
0.8
VIL
V
SHDN Input Leakage Current
±1
µA
SYNC Input Current
±5
µA
ELECTRICAL CHARACTERISTICS
(VDD = PVDD = V SHDN = 5V, VGND = VPGND = 0V, SYNC = GND (FFM), RL = 8Ω, RL connected between OUT+ and OUT-, TA = TMIN
to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)
PARAMETER
Quiescent Current
SYMBOL
CONDITIONS
MIN
IDD
5.2
Shutdown Current
ISHDN
Common-Mode Rejection Ratio
CMRR
f = 1kHz, input referred
Power-Supply Rejection Ratio
PSRR
200mVP-P ripple
Output Power
POUT
Total Harmonic Distortion
Plus Noise
Signal-to-Noise Ratio
THD+N
SNR
TYP
THD+N = 1%
f = 1kHz, either
FFM or SSM
VOUT =
3VRMS
mA
µA
72
dB
72
f = 20kHz
55
RL = 16Ω
700
RL = 8Ω
1200
RL = 6Ω
1600
RL = 8Ω, POUT = 125mW
0.015
RL = 4Ω, POUT = 125mW
0.02
A-weighted
UNITS
0.1
f = 217Hz
BW = 22Hz to
22kHz
MAX
FFM
92.5
SSM
90.5
FFM
95.5
SSM
93.5
dB
mW
%
dB
Note 1: All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design.
Note 2: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For RL = 4Ω, L = 33µH.
For RL = 8Ω, L = 68µH. For RL = 16Ω, L = 136µH.
Note 3: PSRR is specified with the amplifier inputs connected to GND through CIN.
_______________________________________________________________________________________
3
MAX9700
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VDD = 3.3V, SYNC = GND (SSM), TA = +25°C, unless otherwise noted.)
1
1
1
VDD = +3.3V
RL = 8Ω
0.1
POUT = 300mW
POUT = 125mW
0.001
FFM MODE
0.001
0.001
10
100
SSM MODE
0.01
0.01
POUT = 125mW
1k
10k
100k
10
100
1k
10k
10
100k
100
1k
10k
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
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 VOLTAGE
f = 1kHz
f = 100Hz
0.1
0.01
1
f = 10kHz
0.1
VDD = 5V
RL = 4Ω
10
0.5
1.0
1.5
2.0
f = 10kHz
f = 1kHz
0.001
0.001
0
f = 100Hz
0.1
f = 100Hz
f = 1kHz
0.001
1
0.01
0.01
f = 10kHz
MAX9700 toc06
100
MAX9700 toc05
10
THD+N (%)
1
VDD = 5V
RL = 16Ω
THD+N (%)
VDD = 5V
RL = 8Ω
10
100
MAX9700 toc04
100
0
0.2
0.4
0.6
0.8
0
1.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
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
1
DIFFERENTIAL
INPUT
0.1
0.01
FFM
(SYNC = GND)
1
SSM
0.1
0.2
0.3
OUTPUT POWER (W)
0.4
0.5
MAX9700 toc09
1
fSYNC = 800kHz
0.1
0.01
fSYNC = 2MHz
0.001
0.1
10
FFM
(SYNC UNCONNECTED)
0.001
0
VDD = 5V
f = 1kHz
RL = 8Ω
fSYNC = 1.4MHz
0.01
SINGLE ENDED
100
MAX9700 toc08
VDD = 5V
f = 1kHz
RL = 8Ω
10
THD+N (%)
VDD = 2.5V
RL = 8Ω
VCM = 1.25V
NO INPUT CAPACITORS
10
100
MAX9700 toc07
100
THD+N (%)
THD+N (%)
THD+N (%)
THD+N (%)
POUT = 300mW
0.01
4
VDD = +3.3V
RL = 8Ω
POUT = 125mW
0.1
THD+N (%)
0.1
MAX9700 toc03
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX9700 toc02
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX9700 toc01
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
VDD = +5V
RL = 8Ω
THD+N (%)
MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
0.001
0
0.5
1.0
OUTPUT POWER (W)
1.5
2.0
0
0.5
1.0
OUTPUT POWER (W)
_______________________________________________________________________________________
1.5
2.0
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. COMMON-MODE VOLTAGE
80
RL = 8Ω
RL = 4Ω
90
80
60
50
40
VDD = 3.3V
f = 1kHz
10
1.5
2.0
2.5
3.0
0.3
0.6
COMMON-MODE VOLTAGE (V)
EFFICIENCY vs. SUPPLY VOLTAGE
EFFICIENCY (%)
RL = 4Ω
60
50
40
40
20
f = 1kHz
POUT = MAX (THD+N = 1%)
10
0
2.5
3.0
3.5
4.0
4.5
5.0
VDD = 3.3V
f = 1kHz
POUT = 300mW
RL = 8Ω
10
0
5.5
800
1000
1200
1400
1600
1800
f = 1kHz
RL = 4Ω
THD+N = 10%
3.0
RL = 4Ω
THD+N = 1%
2.5
RL = 8Ω
THD+N = 10%
2.0
1.5
1.0
0.5
RL = 8Ω
THD+N = 1%
0
2.5
2000
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
SYNC FREQUENCY (kHz)
SUPPLY VOLTAGE (V)
OUTPUT POWER vs. LOAD RESISTANCE
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
-20
VDD = 5V
CMRR (dB)
1200
800
VDD = 3.3V
INPUT REFERRED
VIN = 200mVP-P
0
-20
-30
-40
-40
-60
-50
-60
-70
-70
400
-80
-80
-90
-90
0
-100
-100
0
10 20 30 40 50 60 70 80 90 100
LOAD RESISTANCE (Ω)
10
100
1k
FREQUENCY (Hz)
10k
100k
OUTPUT REFERRED
INPUTS AC GROUNDED
VDD = 3.3V
-10
-30
-50
5.5
MAX9700TOC18
1600
0
-10
PSRR (dB)
f = 1kHz
THD+N = 1%
MAX9700TOC17
2000
OUTPUT POWER (mW)
50
30
3.5
3.0
2.5
OUTPUT POWER vs.
SUPPLY VOLTAGE
60
20
2.0
EFFICIENCY
vs. SYNC INPUT FREQUENCY
70
30
1.5
OUTPUT POWER (W)
80
RL = 8Ω
70
1.0
0.5
OUTPUT POWER (W)
90
MAX9700toc16
EFFICIENCY (%)
80
VDD = 5V
f = 1kHz
0
1.5
1.2
MAx9700 toc14
90
0.9
100
MAX9700 toc13
100
40
0
0
OUTPUT POWER (W)
1.0
50
10
0
0.5
60
20
20
0
RL = 4Ω
30
30
0.01
RL = 8Ω
70
MAX9700toc15
0.1
70
MAX9700toc12
90
EFFICIENCY (%)
1
100
MAX9700toc11
MAX9700 toc10
VDD = 3.3V
RL = 8Ω
f = 1kHz
POUT = 300mW
DIFFERENTIAL INPUT
EFFICIENCY vs. OUTPUT POWER
EFFICIENCY vs. OUTPUT POWER
100
EFFICIENCY (%)
THD+N (%)
10
10
100
1k
10k
100k
FREQUENCY (Hz)
_______________________________________________________________________________________
5
MAX9700
Typical Operating Characteristics (continued)
(VDD = 3.3V, SYNC = GND (SSM), TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VDD = 3.3V, SYNC = GND (SSM), TA = +25°C, unless otherwise noted.)
OUTPUT FREQUENCY SPECTRUM
GSM POWER-SUPPLY REJECTION
MAX9700 toc19
MAX9700
OUTPUT
OUTPUT MAGNITUDE (dBV)
500mV/div
VDD
100μV/div
MAX9700 toc20
0
FFM MODE
VOUT = -60dBV
f = 1kHz
RL = 8Ω
UNWEIGHTED
-20
-40
-60
-80
-100
-120
-140
0
-40
SSM MODE
VOUT = -60dBV
f = 1kHz
RL = 8Ω
A-WEIGHTED
-20
OUTPUT MAGNITUDE (dBV)
-20
0
MAX9700 toc21
SSM MODE
VOUT = -60dBV
f = 1kHz
RL = 8Ω
UNWEIGHTED
10k
15k
FREQUENCY (Hz)
-60
-80
-100
-40
-60
-80
-100
0
RBW = 10kHz
-10
-20
-30
-40
-50
-60
-70
-80
-120
-140
-140
5k
10k
15k
FREQUENCY (Hz)
-90
-100
0
20k
5k
10k
15k
FREQUENCY (Hz)
WIDEBAND OUTPUT SPECTRUM
(SSM MODE)
MAX9700 toc24
RBW = 10kHz
-20
OUTPUT AMPLITUDE (dB)
1M
10M
100M
FREQUENCY (Hz)
TURN-ON/TURN-OFF RESPONSE
0
-10
20k
MAX9700 toc25
-120
0
SHDN
3V
-30
-40
-50
0V
-60
-70
MAX9700
OUTPUT
-80
250mV/div
-90
-100
1M
10M
100M
FREQUENCY (Hz)
6
20k
WIDEBAND OUTPUT SPECTRUM
(FFM MODE)
OUTPUT FREQUENCY SPECTRUM
OUTPUT FREQUENCY SPECTRUM
0
5k
MAX9700 toc23
DUTY CYCLE = 88%
RL = 8Ω
OUTPUT AMPLITUDE (dB)
2ms/div
MAX9700 toc22
f = 217Hz
INPUT LOW = 3V
INPUT HIGH = 3.5V
OUTPUT MAGNITUDE (dBV)
MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
1G
f = 1kHz
RL = 8Ω
10ms/div
_______________________________________________________________________________________
1G
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
TA = +85°C
5.0
TA = +25°C
4.5
TA = -40°C
4.0
TA = +85°C
0.14
SUPPLY CURRENT (μA)
SUPPLY CURRENT (mA)
5.5
0.16
MAX9700 toc26
6.0
MAX9700 toc27
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
0.12
0.10
TA = +25°C
0.08
0.06
0.04
3.5
TA = -40°C
0.02
0
3.0
2.5
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
5.0
2.5
5.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
Functional Diagram
VDD
1μF
5
(B2) SHDN
1
(A1)
10
(B4)
6
(A3)
VDD
PVDD
SYNC
UVLO/POWER
MANAGEMENT
CLICK-AND-POP
SUPPRESSION
OSCILLATOR
PVDD
1μF
2
(B1) IN+
1μF
3
(C1) IN-
CLASS D
MODULATOR
8
OUT+ (A4)
PGND
PVDD
OUT- 9
(C4)
MAX9700
PGND
PGND
7
(B3)
GND
4
(C2)
( ) UCSP BUMP.
_______________________________________________________________________________________
7
MAX9700
Typical Operating Characteristics (continued)
(VDD = 3.3V, SYNC = GND (SSM), TA = +25°C, unless otherwise noted.)
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
MAX9700
Pin Description
PIN
BUMP
TDFN/µMAX
UCSP
1
2
NAME
FUNCTION
A1
VDD
Analog Power Supply. Connect to an external power supply. Bypass to GND with a
1µF capacitor.
B1
IN+
Noninverting Audio Input
Inverting Audio Input
3
C1
IN-
4
C2
GND
5
B2
SHDN
Active-Low Shutdown Input. Connect to VDD for normal operation.
Analog Ground
6
A3
SYNC
Frequency Select and External Clock Input.
SYNC = GND: Fixed-frequency mode with fS = 1100kHz.
SYNC = Unconnected: Fixed-frequency mode with fS = 1450kHz.
SYNC = VDD: Spread-spectrum mode with fS = 1220kHz ±120kHz.
SYNC = Clocked: Fixed-frequency mode with fS = external clock frequency.
7
B3
PGND
Power Ground
8
A4
OUT+
Amplifier-Output Positive Phase
9
C4
OUT-
Amplifier-Output Negative Phase
10
B4
PVDD
H-Bridge Power Supply. Connect to VDD.
—
—
EP
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.)
Detailed Description
Operating Modes
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, synchronizable switching frequency, and SSM mode create a
compact, 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 harmonics 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
waveform. 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 minimum-width pulse tON(MIN) at the output of
the second 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 output pulse duration remains at tON(MIN). This
causes the net voltage across the speaker (VOUT+ VOUT-) to change.
8
Spread-Spectrum Modulation (SSM) Mode
The MAX9700 features a unique, patented 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 switching
period does not degrade audio reproduction or efficiency (see the Typical Operating Characteristics). Select
SSM mode by setting SYNC = VDD. In SSM mode, the
switching frequency varies randomly by ±120kHz
around the center frequency (1.22MHz). The modulation
_______________________________________________________________________________________
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
MAX9700
tSW
VIN-
VIN+
OUT-
OUT+
tON(MIN)
VOUT+ - VOUT-
Figure 1. MAX9700 Outputs with an Input Signal Applied
Table 1. Operating Modes
SYNC INPUT
MODE
GND
FFM with fS = 1100kHz
UNCONNECTED
FFM with fS = 1450kHz
VDD
Clocked
SSM with fS = 1220kHz ±120kHz
FFM with fS = external clock frequency
scheme remains the same, but the period of the sawtooth 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).
External Clock Mode
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 synchronizes 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.
Filterless Modulation/Common-Mode Idle
The MAX9700 uses Maxim’s unique, patented 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
_______________________________________________________________________________________
9
MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
tSW
tSW
tSW
tSW
VIN-
VIN+
OUT-
OUT+
tON(MIN)
VOUT+ - VOUT-
Figure 2. MAX9700 Output with an Input Signal Applied (SSM Mode)
output a 50% duty cycle square wave when no signal is
present. With no filter, the square wave appears across
the load as a DC voltage, 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.
Efficiency
Efficiency of a class D amplifier is attributed to the
region of operation of the output stage transistors. In a
class D amplifier, the output transistors act as currentsteering switches and consume negligible additional
power. Any power loss associated with the class D output stage is mostly due to the I ✕ 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).
Idle Mode is a trademark of Maxim Integrated Products.
10
______________________________________________________________________________________
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
MAX9700
VIN = 0V
50.0
AMPLITUDE (dBμV/m)
45.0
40.0
35.0
30.0
OUT-
25.0
20.0
15.0
10.0
30.0
OUT+
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)
VOUT+ - VOUT- = 0V
Figure 4. MAX9700 Outputs with No Input Signal
Figure 3. MAX9700 EMI Spectrum
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
mode. Connect SHDN to VDD for normal operation.
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, preventing clicks and pops when the H-bridge is subsequently enabled. For 35ms following startup, a soft-start
function gradually unmutes the input amplifiers.
Applications Information
90
80
EFFICIENCY (%)
Click-and-Pop Suppression
EFFICIENCY vs. OUTPUT POWER
100
MAX9700
70
60
50
CLASS AB
40
30
VDD = 3.3V
f = 1kHz
RL - 8Ω
20
10
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
OUTPUT POWER (W)
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 amplifier, and can decrease efficiency. The traditional PWM
scheme uses large differential output swings (2 x VDD
peak-to-peak) and causes large ripple currents. Any
parasitic 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.
Because the frequency of the MAX9700 output is well
beyond the bandwidth of most speakers, voice coil
movement 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.
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
______________________________________________________________________________________
11
MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
the 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-current draw of 8µW/(VDD/100η), which is on the
order of a few microamps.
1μF
SINGLE-ENDED
AUDIO INPUT
IN+
MAX9700
IN1μF
Input Amplifier
Differential Input
The MAX9700 features a differential input structure,
making it compatible with many CODECs, and offering
improved noise immunity over a single-ended input
amplifier. 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 amplifier’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.
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
component 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.
Component Selection
Input Filter
An input capacitor, CIN, in conjunction with the input
impedance of the MAX9700 forms a highpass filter that
removes the DC bias from an incoming signal. The ACcoupling capacitor allows the amplifier to bias the signal to an optimum DC level. Assuming zero source
impedance, the -3dB point of the highpass filter is
given by:
f−3dB =
1
2πRINCIN
Choose CIN so f-3dB is well below the lowest frequency
of interest. Setting f-3dB too high affects the low-frequency response of the amplifier. Use capacitors
12
Figure 6. Single-Ended Input
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
cellular 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.
Output Filter
The MAX9700 does not require an output filter. The
device passes FCC emissions standards with 100mm
of unshielded speaker cables. However, output filtering
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.
Supply Bypassing/Layout
Proper power-supply bypassing ensures low-distortion
operation. For optimum performance, bypass VDD to
GND and PVDD to PGND with separate 0.1µF capacitors as close to each pin as possible. A low-impedance, high-current power-supply connection to PVDD is
assumed. Additional bulk capacitance should be
added as required depending on the application and
power-supply characteristics. GND and PGND should
be star connected to system ground. Refer to the
MAX9700 evaluation kit for layout guidance.
______________________________________________________________________________________
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
1μF
RIGHT-CHANNEL
DIFFERENTIAL
AUDIO INPUT
VDD
PVDD
IN+
MAX9700 OUT+
IN-
OUTSYNC
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 volume 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
LEFT-CHANNEL
DIFFERENTIAL
AUDIO INPUT
VDD
PVDD
IN+
MAX9700 OUT+
IN-
OUTSYNC
Figure 7. Master-Slave Stereo Configuration
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
CROSSTALK vs. FREQUENCY
0
100
VDD = 3.3V
f = 1kHz
RL = 8Ω
SLAVE DEVICE
CROSSTALK (dB)
THD+N (%)
10
VDD = 3.3V
RL = 8Ω
f = 1kHz
VIN = 500mVP-P
-20
1
0.1
-40
MASTER-TO-SLAVE
-60
-80
-100
0.01
SLAVE-TO-MASTER
-120
0.001
0
0.1
0.2
0.3
OUTPUT POWER (W)
Figure 8. Master-Slave THD+N
0.4
0.5
10
100
1k
10k
100k
FREQUENCY (Hz)
Figure 9. Master-Slave Crosstalk
______________________________________________________________________________________
13
MAX9700
Stereo Configuration
Two MAX9700s can be configured as a stereo amplifier
(Figure 7). Device U1 is the master amplifier; its unfiltered 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 performance 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.
VDD
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 similar 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 construction,
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.maxim-ic.com/ucsp.
1μF
CW
22kΩ
1μF
IN-
50kΩ
IN-
CW
50kΩ
MAX9700
1μF
IN+
MAX9700
IN+
22kΩ
1μF
Figure 10b. Improved Single-Ended Drive of MAX9700 Plus
Volume
Figure 10a. Single-Ended Drive of MAX9700 Plus Volume
Selector Guide
Ordering Information (continued)
PART
TEMP RANGE
PINPACKAGE
TOP
MARK
PIN-PACKAGE
GAIN (dB)
MAX9700AETB
10 TDFN-EP*
6
ACN
MAX9700AEUB
10 µMAX
6
PART
MAX9700CETB
-40oC to +85oC
10 TDFN-EP*
MAX9700CEUB
-40oC to +85oC
10 µMAX
—
MAX9700AEBC-T
MAX9700CEBC-T
-40oC to +85oC
12 UCSP
—
MAX9700BETB
MAX9700DETB
-40oC to +85oC
10 TDFN-EP*
ACO
MAX9700BEUB
10 µMAX
12
MAX9700DEUB
-40oC to +85oC
10 µMAX
—
MAX9700BEBC-T
12 UCSP
12
MAX9700DEBC-T
-40oC to +85oC
12 UCSP
—
MAX9700CETB
10 TDFN-EP*
15.6
*EP = Exposed pad.
12 UCSP
6
10 TDFN-EP*
12
MAX9700CEUB
10 µMAX
15.6
MAX9700CEBC-T
12 UCSP
15.6
10 TDFN-EP*
20
MAX9700DETB
MAX9700DEUB
10 µMAX
20
MAX9700DEBC-T
12 UCSP
20
*EP = Exposed pad.
14
______________________________________________________________________________________
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
VDD
1μF
VDD
VDD
0.1μF
AUX_IN
PVDD
IN+
OUT
2.2kΩ
OUT+
IN-
OUT-
SHDN
SYNC
CODEC/
BASEBAND
PROCESSOR
OUT
BIAS
MAX9700
2.2kΩ
MAX4063
0.1μF
IN+
VDD
IN0.1μF
1μF
VDD
SHDN
1μF
INL
OUTL
1μF
MAX9722
INR
μCONTROLLER
OUTR
PVSS
SVSS
C1P
CIN
1μF
1μF
Pin Configurations (continued)
TOP VIEW
(BUMP SIDE DOWN)
1
TRANSISTOR COUNT: 3595
PROCESS: BiCMOS
MAX9700
2
VDD
Chip Information
3
4
SYNC
OUT+
PGND
PVDD
A
IN+
SHDN
IN-
GND
B
OUT-
C
UCSP
______________________________________________________________________________________
15
MAX9700
System Diagram
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
12 UCSP
B12-11
21-0104
10 TDFN-EP
T1033-1
21-0137
10 µMAX
U10-2
21-0061
12L, UCSP 4x3.EPS
MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
PACKAGE OUTLINE, 4x3 UCSP
21-0104
16
______________________________________________________________________________________
F
1
1
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
6, 8, &10L, DFN THIN.EPS
______________________________________________________________________________________
17
MAX9700
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
18
COMMON DIMENSIONS
PACKAGE VARIATIONS
SYMBOL
MIN.
MAX.
PKG. CODE
N
D2
E2
e
JEDEC SPEC
b
[(N/2)-1] x e
A
0.70
0.80
T633-2
6
1.50–0.10
2.30–0.10
0.95 BSC
MO229 / WEEA
0.40–0.05
1.90 REF
D
2.90
3.10
T833-2
8
1.50–0.10
2.30–0.10
0.65 BSC
MO229 / WEEC
0.30–0.05
1.95 REF
E
2.90
3.10
T833-3
8
1.50–0.10
2.30–0.10
0.65 BSC
MO229 / WEEC
0.30–0.05
1.95 REF
A1
0.00
0.05
T1033-1
10
1.50–0.10
2.30–0.10
0.50 BSC
MO229 / WEED-3
0.25–0.05
2.00 REF
L
0.20
0.40
T1033-2
10
1.50–0.10
2.30–0.10
0.50 BSC
MO229 / WEED-3
0.25–0.05
2.00 REF
k
0.25 MIN.
T1433-1
14
1.70–0.10
2.30–0.10
0.40 BSC
----
0.20–0.05
2.40 REF
A2
0.20 REF.
T1433-2
14
1.70–0.10
2.30–0.10
0.40 BSC
----
0.20–0.05
2.40 REF
______________________________________________________________________________________
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
10LUMAX.EPS
α
α
______________________________________________________________________________________
19
MAX9700
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
MAX9700
1.2W, Low-EMI, Filterless,
Class D Audio Amplifier
Revision History
REVISION
NUMBER
REVISION DATE
0
10/03
Initial release
1
6/04
Changes made to TOCs and specs
2
10/08
Addition of EP information to pin description
table
DESCRIPTION
PAGES CHANGED
—
3–8, 14, 15
1, 2, 3, 8, 14
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.