General Description
The MAX9791 combines a stereo 2W Class D power
amplifier, a stereo 180mW DirectDrive®headphone
amplifier, and a 120mA low-dropout (LDO) linear regu-
lator in a single device. The MAX9792 combines a
mono 3W Class D power amplifier, a stereo 180mW
DirectDrive headphone amplifier, and a 120mA LDO
linear regulator in a single device.
The MAX9791/MAX9792 feature Maxim’s DirectDrive
headphone amplifier architecture that produces a
ground-referenced output from a single supply, eliminat-
ing the need for large DC-blocking capacitors, saving
cost, board space, and component height. High 107dB
DC PSRR and low 0.006% THD+N ensure clean, low-
distortion amplification of the audio signal.
The ground sense feature senses and corrects for the
voltage difference between the output jack ground and
device signal ground. This feature minimizes head-
phone amplifier crosstalk by sensing the impedance in
the ground return trace and correcting for it at the out-
put jack. This feature also minimizes ground-loop noise
when the output socket is used as a line out connection
to other grounded equipment (for example, a PC con-
nected to a home hi-fi system).
The MAX9791/MAX9792 feature low RF susceptibility,
allowing the amplifiers to successfully operate in close
proximity to wireless applications. The MAX9791/
MAX9792 Class D amplifiers feature Maxim’s spread-
spectrum modulation and active emissions limiting cir-
cuitry. Industry-leading click-and-pop suppression
eliminates audible transients during power-up and shut-
down cycles.
The MAX9791/MAX9792 wake-on-beep feature wakes
up the speaker and headphone amplifiers when a qual-
ified beep signal is detected at the BEEP input.
For maximum flexibility, separate speaker and head-
phone amplifier control inputs provide independent
shutdown of the speaker and headphone amplifiers.
Additionally the LDO can be enabled independently of
the audio amplifiers.
The MAX9791/MAX9792 feature thermal-overload and
output short-circuit protection. The devices are avail-
able in 28-pin TQFN packages and are specified over
the -40°C to +85°C extended temperature range.
Applications
Notebook Computers
Tablet PCs
Portable Multimedia Players
Features
oWindows Vista® Premium Compliant
oLow EMI Filterless Class D Speaker Amplifiers
Pass EN55022B Emissions Limit with 30cm of
Speaker Cable
o180mW DirectDrive Headphone Amplifier
oExcellent RF Immunity
oIntegrated 120mA LDO
oEliminates Headphone Ground Loop Noise
oWake-on-Beep Function
oClick-and-Pop Suppression
oShort-Circuit and Thermal-Overload Protection
oThermally Efficient, Space-Saving Package
28-Pin TQFN-EP (4mm x 4mm x 0.75mm)
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
________________________________________________________________
Maxim Integrated Products
1
19-4217; Rev 1; 6/10
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Ordering Information
PART STEREO/
MONO
LDO
OUTPUT PIN-PACKAGE
MAX9791AETI+ Stereo 4.75V 28 TQFN-EP*
MAX9791BETI+ Stereo 3.3V 28 TQFN-EP*
MAX9791CETI+ Stereo 1.8V 28 TQFN-EP*
MAX9792AETI+ Mono 4.75V 28 TQFN-EP*
MAX9792CETI+ Mono 1.8V 28 TQFN-EP*
Note: All devices are specified over the -40°C to +85°C
extended temperature range.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
*
EP = Exposed pad.
DirectDrive is a registered trademark of Maxim Integrated
Products, Inc.
Windows Vista is a registered trademark of Microsoft Corp.
MAX9791
SPKR_EN
HP_EN
LDO_EN
BEEP
SPEAKER AND LDO
SUPPLY
2.7V TO 5.5V
HEADPHONE SUPPLY
2.7V TO 5.5V
AVDD
LDO 1.8V, 3.3V, OR 4.75V
CLASS D
AMP
CLASS D
AMP
Simplified Block Diagrams
Simplified Block Diagrams continued at end of data sheet.
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2µF (CLDO = 4µF for 1.8V LDO option),
C1 = C2 = 1µF. RL= ∞, unless otherwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF,
CIN2 =C
COM = 1µF, TA= TMIN to TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 3)
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.
Supply Voltage
(AVDD, PVDD, HPVDD to GND)........................-0.3V to +6.0V
(AVDD to PVDD) .............................................................±0.3V
GND to PGND, CPGND ......................................................±0.3V
CPVSS, C1N to GND ............................................-6.0V to + 0.3V
HPL, HPR to CPVSS ...........................................-0.3V to lower of
(HPVDD - CPVSS + 0.3V) and +9V
HPL, HPR to HPVDD..................................+0.3V to the higher of
(CPVSS - HPVDD - 0.3V) and -9V
COM, SENSE........................................................-0.3V to + 0.3V
Any Other Pin ..........................................-0.3V to (AVDD + 0.3V)
Duration of Short Circuit between OUT_+, OUT_- and GND,
PGND, AVDD, or PVDD..........................................Continuous
Duration of Short Circuit between LDO_OUT and AVDD,
GND (Note 1) .........................................................Continuous
Duration of Short Circuit between HPR, HPL and
GND .......................................................................Continuous
Continuous Current (PVDD, OUT_+, OUT_-, PGND)............1.7A
Continuous Current (C1N, C1P, CPVSS, AVDD, HPVDD,
LDO_OUT, HPR, HPL) ..................................................850mA
Continuous Input Current (All Other Pins) ........................±20mA
Continuous Power Dissipation (TA= +70°C)
28-Pin Thin QFN Single-Layer Board (derate 20.8mW/°C
above +70°C)..........................................................1667mW
Junction-to-Ambient Thermal Resistance (θJA)
(Note 2) .....................................................................40°C/W
Junction-to-Case Thermal Resistance (θJC)
(Note 2) ....................................................................2.7°C/W
28-Pin Thin QFN Multilayer Board (derate 28.6mW/°C
above +70°C)..........................................................2286mW
Junction-to-Ambient Thermal Resistance (θJA)
(Note 2) .....................................................................35°C/W
Junction-to-Case Thermal Resistance (θJC)
(Note 2) ....................................................................2.7°C/W
ESD Protection, Human Body Model ...................................±2kV
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
GENERAL
Supply Voltage VAVDD,
VPVDD Guaranteed by PSRR test (Note 4) 2.7 5.5 V
Headphone Supply Voltage VHPVDD Guaranteed by PSRR test 2.7 5.5 V
Undervoltage Lockout UVLO 2.65 V
SPKR_EN HP_EN LDO_EN
1 0 1 250 400 µA
1 1 0 4.4 6
0 0 0 10.5 15
MAX9791
0 1 0 14.4 21
mA
1 0 1 250 400 µA
1 1 0 4.4 6
0 0 0 10.5 18
Quiescent Current
IAVDD +
IPVD +
IHPVDD
MAX9792
0 1 0 14.4 24
mA
Shutdown Current ISHDN SPKR_EN = 1.8V 3.3 7..3 µA
Bias Voltage VBIAS HP_INR, HP_INL, SPKR_INR, SPKR_INL 0 V
Note 1: If short is present at power-up.
Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
_______________________________________________________________________________________ 3
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Shutdown to Full Operation tON 0.4 ms
Overtemperature Threshold +150 °C
SPEAKER AMPLIFIER
RL = 4
(MAX9791) 1.7
RL = 8
(MAX9791) 1.2
THD+N = 1%,
f = 1kHz,
TA = +25°C
(Note 5) RL = 3
(MAX9792) 3
RL = 4
(MAX9791) 2.2
RL = 8
(MAX9791) 1.5
Output Power POUT
THD+N = 10%,
f = 1kHz,
TA = +25°C
(Note 5) RL = 3
(MAX9792) 3.7
W
RL = 8, POUT = 500mW, f = 1kHz (Note 5) 0.04
Total Harmonic Distortion Plus
Noise THD+N RL = 4, POUT = 500mW, f = 1kHz (Note 5) 0.03 %
VAVDD = VPVDD = 2.7V to 5.5V, TA = +25°C 60 80
f = 217Hz, 200mVP-P 73
f = 1kHz, 200mVP-P 75
Power-Supply Rejection Ratio PSRR
f = 10kHz, 200mVP-P 62
dB
Feedback Impedance RFSKR Guaranteed by design 20 k
Gain AV R
IN1 = 20k 12 dB
Output Offset Voltage VOS Measured between OUT_+ and OUT_-,
TA = +25°C ±3 ±10 mV
Into shutdown -52.4
Click-and-Pop Level KCP
RL = 8,
peak voltage,
A-weighted,
32 samples per second
(Notes 5, 6, and 7)
Out of
shutdown -54
dBV
A-weighted 98
Signal-to-Noise Ratio SNR
RL = 8
POUT = 1.2W fIN = 1kHz,
(Note 5) 20Hz to 20kHz 94
dB
Noise VN A-weighted 38 µVRMS
L to R, R to L, RL = 8, VIN = -20dBFS =
100mVRMS, fIN = 1kHz (Note 5) 78
L to R, R to L, RL = 8, VIN = -20dBFS =
100mVRMS, fIN = 15kHz (Note 5) 70
Crosstalk
HP to SPKR, RLSPKR = 8, PHP = 20mW,
RLHP = 32, fIN = 1kHz (Note 5) 77
dB
ELECTRICAL CHARACTERISTICS (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2µF (CLDO = 4µF for 1.8V LDO option),
C1 = C2 = 1µF. RL= ∞, unless otherwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF,
CIN2 =C
COM = 1µF, TA= TMIN to TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 3)
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
4 _______________________________________________________________________________________
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Class D Switching Frequency fSPK 948 1158 kHz
Spread-Spectrum Bandwidth ±15 kHz
Efficiency P
OUT = 1.5W, fIN = 1kHz, RL = 8 (Note 5) 83 %
HEADPHONE AMPLIFIER
RL = 16 100
Output Power POUT
THD+N = 1%,
f = 1kHz,
TA = +25°CRL = 32 180
mW
RL = 32, fIN = 6kHz, 20kHz AES17,
VIN = -3dBFS = 212mVRMS -78
RL = 10k, fIN = 6kHz, 20kHz AES17,
VIN = -3dBFS = 500mVRMS -87
dBFS
RL = 32, POUT = 100mW, f = 1kHz 0.006
Total Harmonic Distortion Plus
Noise THD+N
RL = 16, POUT = 75mW, f = 1kHz 0.014 %
VHPVDD = 2.7V to 5.5V, TA = +25°C 70 107
f = 1kHz, VRIPPLE = 200mVP-P 91
Power-Supply Rejection Ratio PSRR
f = 10kHz, VRIPPLE = 200mVP-P 80
dB
Feedback Impedance RFHP 38.2 40.2 42.2 k
Gain AV R
IN2 = 40.2k 0 dB
Output Offset Voltage VOS TA = +25°C ±0.3 ±3 mV
Into shutdown -81
Click-and-Pop Level KCP
RL = 32,
peak voltage,
A-weighted, 32 samples
per second (Notes 6, 7)
Out of
shutdown -72.5
dBV
A-weighted 102
Signal-to-Noise Ratio SNR RL = 32, POUT = 40mW,
fIN = 1kHz 20Hz to 20kHz 94 dB
Noise VN A-weighted 8 µVRMS
Maximum Capacitive Load CL No sustained oscillations 100 pF
RL = 32, VIN =
-20dBFS = 30mVRMS 82
L to R, R to L, fIN
= 1kHz, COM
and SENSE
connected
RL = 10k, VIN =
-20dBFS = 0.7mVRMS 89
RL = 32, VIN =
-20dBFS = 30mVRMS 64
L to R, R to L, fIN
= 15kHz, COM
and SENSE
connected
RL = 10k, VIN =
-20dBFS = 70.7mVRMS 70
Crosstalk
SPKR to HP, RLSPKR = 8, PSPKR = 1W,
RLHP = 32, fIN = 1Hz 80
dB
ELECTRICAL CHARACTERISTICS (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2µF (CLDO = 4µF for 1.8V LDO option),
C1 = C2 = 1µF. RL= ∞, unless otherwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF,
CIN2 =C
COM = 1µF, TA= TMIN to TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 3)
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
_______________________________________________________________________________________ 5
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
COM Input Range VCOM Inferred from CMRR test -300 +300 mV
Common-Mode Rejection Ratio CMRR -300mV < VCOM < +300mV 60 dB
Slew Rate SR 0.38 V/µs
Charge-Pump Frequency fOSC 530 kHz
BEEP INPUT (LDO_EN = 1)
Beep Signal Minimum fBEEP Four-cycle count 215 Hz
Amplifier Turn-On Time tONBEEP 0.4 ms
Amplifier Hold Time tHOLDBEEP 221 246 271 ms
LOW-DROPOUT LINEAR REGULATOR
LDO Ground Current ILDO 0.25 0.4 mA
Output Current IOUT Inferred from load regulation 120 mA
Current Limit ILIM 300 mA
Crosstalk
Speaker to LDO, VLDO_OUT = 4.75V,
f =1kHz, ILDO_OUT = 10mA, speaker POUT
= 1.2W, RL = 8 (Note 6)
-80 dB
VLDO_OUT = 4.75V ±1.5
Output-Voltage Accuracy VLDO_OUT = 3.3V ±1.5 %
IOUT = 50mA 46
Dropout Voltage VDO VLDO_OUT = 4.75V,
TA = +25°C (Note 8) IOUT = 120mA 106 mV
Startup Time 30 µs
VAVDD = 5V to 5.5V, VLDO_OUT = 4.75V,
ILDO_OUT = 1mA, CLDO = 2µF -4.8 1.5 +4.8
VAVDD = 4.5V to 5.5V, VLDO_OUT = 3.3V,
ILDO_OUT = 1mA, CLDO = 2µF -4 0.2 +4
Line Regulation
VAVDD = 3V to 5.5V, VLDO_OUT = 1.8V,
ILDO_OUT = 1mA, CLDO = 4µF -6.4 2.5 +6.4
mV/V
Load Regulation VLDO_OUT = 4.75V, 1mA < ILDO_OUT <
120mA 0.22 mV/mA
f = 1kHz 56
Ripple Rejection
VRIPPLE = 200mVP-P,
VLDO_OUT = 4.75V
ILDO_OUT = 10mA f = 10kHz 40
dB
Output-Voltage Noise 20Hz to 20kHz, CLDO_OUT = 2 x 1µF,
ILDO_OUT = 120mA 130 µVRMS
DIGITAL INPUTS (SPKR_EN, HP_EN, LDO_EN, BEEP)
Input-Voltage High VINH 1.4 V
Input-Voltage Low VINL 0.4 V
Input Bias Current -1 +1 µA
ELECTRICAL CHARACTERISTICS (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2µF (CLDO = 4µF for 1.8V LDO option),
C1 = C2 = 1µF. RL= ∞, unless otherwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF,
CIN2 =C
COM = 1µF, TA= TMIN to TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 3)
Typical Operating Characteristics
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.)
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
6 _______________________________________________________________________________________
Note 3: All devices are 100% production tested at room temperature. All temperature limits are guaranteed by design.
Note 4: AVDD and PVDD must be tied together. If LDO is enabled, set AVDD and PVDD as specified in the Line Regulation row of
the
Electrical Characteristics
table.
Note 5: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For RL= 3Ω, L = 22µH.
For RL= 4Ω, L = 33µH. For RL= 8Ω, L = 68µH.
Note 6: Specified at TA= +25°C with an 8Ω+ 68µH load connected across BTL output for speaker amplifier. Specified at TA= +25°C
with a 32Ωresistive load connected between HPR, HPL and GND for headphone amplifier. Speaker and headphone mode
transitions are controlled by SPKR_EN and HP_EN inputs, respectively.
Note 7: Amplifier Inputs AC-coupled to GND.
Note 8: Guaranteed by ATE characterization; limits are not production tested.
TOTAL HARMONIC DISTORTION + NOISE
vs. FREQUENCY (MAX9792 SPEAKER MODE)
MAX9791 toc01
FREQUENCY (kHz)
THD+N (dBFS)
0.1 1 10
-90
-80
-50
-40
-30
-70
-60
-20
-10
0
-100
0.01 100
RL = 3Ω
VIN = -3dBFS
FS = 707mVRMS
FS = 1VRMS
TOTAL HARMONIC DISTORTION + NOISE
vs. FREQUENCY (MAX9791 SPEAKER MODE)
MAX9791 toc02
FREQUENCY (kHz)
THD+N (dBFS)
0.1 1 10
-90
-80
-50
-40
-30
-70
-60
-20
-10
0
-100
0.01 100
RL = 4Ω
VIN = -3dBFS
FS = 707mVRMS
FS = 1VRMS
TOTAL HARMONIC DISTORTION + NOISE
vs. FREQUENCY (MAX9791 SPEAKER MODE)
MAX9791 toc03
FREQUENCY (kHz)
THD+N (dBFS)
0.1 1 10
-90
-80
-50
-40
-30
-70
-60
-20
-10
0
-100
0.01 100
RL = 8Ω
VIN = -3dBFS
FS = 707mVRMS
FS = 1VRMS
TOTAL HARMONIC DISTORTION + NOISE
vs. OUTPUT POWER (MAX9792 SPEAKER MODE)
MAX9791 toc04
OUTPUT POWER (W)
THD+N (%)
1.0 2.0 3.0
0.01
0.1
1
10
100
0.001
0 4.00.5 1.5 2.5 3.5
RL = 3Ω
f = 6kHz
f = 1kHz
f = 100Hz
TOTAL HARMONIC DISTORTION + NOISE
vs. OUTPUT POWER (MAX9791 SPEAKER MODE)
MAX9791 toc05
OUTPUT POWER (W)
THD+N (%)
2.01.51.0
0.01
0.1
1
10
100
0.001
0 3.02.50.5
RL = 4Ω
f = 6kHz
f = 1kHz
f = 100Hz
TOTAL HARMONIC DISTORTION + NOISE
vs. OUTPUT POWER (MAX9791 SPEAKER MODE)
MAX9791 toc06
OUTPUT POWER (W)
THD+N (%)
0.5 1.0
0.01
0.1
1
10
100
0.001
02.01.5
RL = 8Ω
f = 6kHz
f = 1kHz
f = 100Hz
ELECTRICAL CHARACTERISTICS (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2µF (CLDO = 4µF for 1.8V LDO option),
C1 = C2 = 1µF. RL= ∞, unless otherwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF,
CIN2 =C
COM = 1µF, TA= TMIN to TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 3)
SPEAKER
Typical Operating Characteristics (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.)
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
_______________________________________________________________________________________
7
OUTPUT POWER vs. LOAD RESISTANCE
(MAX9792 SPEAKER MODE)
MAX9791 toc07
LOAD RESISTANCE (Ω)
OUTPUT POWER (W)
10
1.0
2.0
3.0
4.0
5.0
0
1.5
2.5
3.5
4.5
0.5
1 100
f = 1kHz
THD+N = 10%
THD+N = 1%
OUTPUT POWER vs. LOAD RESISTANCE
(MAX9792 SPEAKER MODE)
MAX9791 toc07a
LOAD RESISTANCE (Ω)
OUTPUT POWER (W)
10
0.5
1.0
1.5
2.0
2.5
0
1100
VPVDD = VAVDD = 3.7V
THD+N = 10%
THD+N = 1%
OUTPUT POWER vs. LOAD RESISTANCE
(MAX9791 SPEAKER MODE)
MAX9791 toc08
LOAD RESISTANCE (Ω)
OUTPUT POWER (W)
10
1.0
2.0
3.0
0
1.5
2.5
0.5
1 100
f = 1kHz
THD+N = 10%
THD+N = 1%
OUTPUT POWER vs. LOAD RESISTANCE
(MAX9791 SPEAKER MODE)
MAX9791 toc08a
LOAD RESISTANCE (Ω)
OUTPUT POWER (W)
10
0.25
0.50
0.75
1.00
1.25
1.50
0
1 100
VPVDD = VAVDD = 3.7V
THD+N = 10%
THD+N = 1%
EFFICIENCY vs. OUTPUT POWER
(MAX9792 SPEAKER MODE)
MAX9791 toc09
OUTPUT POWER (W)
EFFICIENCY (%)
1.0 2.0 3.0
70
80
90
100
110
20
10
30
40
50
60
0
04.00.5 1.5 2.5 3.5
RL = 8Ω
RL = 3Ω
fIN = 1kHz
EFFICIENCY vs. OUTPUT POWER
(MAX9792 SPEAKER MODE)
MAX9791 toc09a
OUTPUT POWER (W)
EFFICIENCY (%)
1.20.90.60.3
10
20
30
40
50
60
70
80
90
0
01.5
VPVDD = VAVDD = 3.7V
fIN = 1kHz
RL = 8Ω
RL = 3Ω
EFFICIENCY vs. OUTPUT POWER
(MAX9791 SPEAKER MODE)
MAX9791 toc10
OUTPUT POWER (W)
EFFICIENCY (%)
1.50.90.6
70
80
90
100
20
10
30
40
50
60
0
01.81.20.3
RL = 8Ω
RL = 4Ω
fIN = 1kHz
EFFICIENCY vs. OUTPUT POWER
(MAX9791 SPEAKER MODE)
MAX9791 toc10a
OUTPUT POWER (W)
EFFICIENCY (%)
0.80.60.40.2
10
20
30
40
50
60
70
80
90
0
01.0
VPVDD = VAVDD = 3.7V
fIN = 1kHz
RL = 8Ω
RL = 4Ω
SPEAKER
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
8 _______________________________________________________________________________________
OUTPUT POWER vs. SUPPLY VOLTAGE
(MAX9791 SPEAKER MODE)
MAX9791 toc10b
SUPPLY VOLTAGE (V)
OUTPUT POWER (W)
5.04.54.03.53.0
0.5
1.0
1.5
2.0
2.5
3.0
0
2.5 5.5
f = 1kHz
RLOAD = 4Ω
THD+N = 10%
THD+N = 1%
OUTPUT POWER vs. SUPPLY VOLTAGE
(MAX9791 SPEAKER MODE)
MAX9791 toc10c
SUPPLY VOLTAGE (V)
OUTPUT POWER (W)
5.04.54.03.53.0
0.5
1.0
1.5
2.0
0
2.5 5.5
f = 1kHz
RLOAD = 8Ω
THD+N = 10%
THD+N = 1%
OUTPUT POWER vs. SUPPLY VOLTAGE
(MAX9792 SPEAKER MODE)
MAX9791 toc10d
SUPPLY VOLTAGE (V)
OUTPUT POWER (W)
5.04.54.03.53.0
0.5
1.0
1.5
2.0
2.5
0
2.5 5.5
f = 1kHz
RLOAD = 8Ω
THD+N = 10%
THD+N = 1%
OUTPUT POWER vs. SUPPLY VOLTAGE
(MAX9792 SPEAKER MODE)
MAX9791 toc10e
SUPPLY VOLTAGE
OUTPUT POWER (W)
5.04.54.03.53.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0
2.5 5.5
f = 1kHz
RLOAD = 3Ω
THD+N = 10%
THD+N = 1%
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY (SPEAKER MODE)
MAX9791 toc11
FREQUENCY (kHz)
PSRR (dB)
1
-30
-20
-10
-80
-90
-70
-60
-50
-40
-100
0.01 100
LEFT
RIGHT
0.1 10
0
VRIPPLE = 200mVP-P
RL = 8Ω
CROSSTALK vs. FREQUENCY
(SPEAKER MODE)
MAX9791 toc12
FREQUENCY (kHz)
CROSSTALK (dB)
1
-30
-20
-10
-80
-90
-100
-70
-60
-50
-40
-110
0.01 100
RIGHT TO LEFT
LEFT TO RIGHT
0.1 10
0
FS = 1VRMS
VIN = -20dBFS
RL = 8Ω
Typical Operating Characteristics (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.)
SPEAKER
Typical Operating Characteristics (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.)
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
_______________________________________________________________________________________
9
SPEAKER STARTUP WAVEFORM
MAX9791 toc13
SPKR_EN
2V/div
SPEAKER OUT
200
µ
s/div
SPEAKER SHUTDOWN WAVEFORM
MAX9791 toc14
SPKR_EN
2V/div
SPEAKER OUT
200
µ
s/div
WIDEBAND OUTPUT SPECTRUM
(SPEAKER MODE)
MAX9791 toc15
FREQUENCY (MHz)
OUTPUT AMPLITUDE (dBV)
101
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-120
0 100
RBW = 1kHz
INPUT AC GROUNDED
OUTPUT FREQUENCY SPECTRUM
(SPEAKER MODE)
MAX9791 toc16
FREQUENCY (kHz)
OUTPUT MAGNITUDE (dBV)
10
-100
-60
0
-140
-80
-40
-20
-120
120515
VOUT = -60dBV
f = 1kHz
RL = 8Ω
UNWEIGHTED
SPEAKER
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
10 ______________________________________________________________________________________
TOTAL HARMONIC DISTORTION + NOISE
vs. FREQUENCY (HEADPHONE MODE)
MAX9791 toc17
FREQUENCY (kHz)
THD+N (dBFS)
1
-80
-90
-70
-60
-100
0.01 100
FS = 300mVRMS
FS = 1VRMS
0.1 10
-50
RL = 16Ω
VIN = -3dBFS
TOTAL HARMONIC DISTORTION + NOISE
vs. FREQUENCY (HEADPHONE MODE)
MAX9791 toc18
FREQUENCY (kHz)
THD+N (dBFS)
1
-80
-90
-70
-60
-100
0.01 100
FS = 300mVRMS
FS = 1VRMS
0.1 10
-50
VHPVDD = 3V
RL = 16Ω
VIN = -3dBFS
TOTAL HARMONIC DISTORTION + NOISE
vs. FREQUENCY (HEADPHONE MODE)
MAX9791 toc19
FREQUENCY (kHz)
THD+N (dBFS)
1
-80
-90
-70
-60
-100
0.01 100
FS = 300mVRMS
FS = 1VRMS
0.1 10
-50
RL = 32Ω
VIN = -3dBFS
TOTAL HARMONIC DISTORTION + NOISE
vs. FREQUENCY (HEADPHONE MODE)
MAX9791 toc20
FREQUENCY (kHz)
THD+N (dBFS)
1
-80
-90
-70
-60
-100
0.01 100
FS = 300mVRMS
FS = 1VRMS
0.1 10
-50
VHPVDD = 3V
RL = 32Ω
VIN = -3dBFS
TOTAL HARMONIC DISTORTION + NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
MAX9791 toc21
OUTPUT POWER (mW)
THD+N (%)
160
0.1
0.01
1
10
0.001
0 200
f = 6kHz
f = 1kHz
f = 100Hz
12040 80
100
RL = 16Ω
TOTAL HARMONIC DISTORTION + NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
MAX9791 toc22
OUTPUT POWER (mW)
THD+N (%)
0.1
0.01
1
10
0.001
050 250
f = 6kHz
f = 1kHz
f = 100Hz
200
150
100
100
RL = 32Ω
TOTAL HARMONIC DISTORTION + NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
MAX9791 toc23
OUTPUT POWER (mW)
THD+N (%)
10
0.1
0.01
1
10
0.001
05040 90
f = 6kHz
f = 1kHz
f = 100Hz
80
70
603020
100
VHPVDD = 3V
RL = 16Ω
TOTAL HARMONIC DISTORTION + NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
MAX9791 toc24A
OUTPUT POWER (mW)
THD+N (%)
10
0.1
0.01
1
10
0.001
05040 70
f = 6kHz
f = 1kHz
f = 100Hz
603020
100
VHPVDD = 3V
RL = 32Ω
OUTPUT POWER vs. LOAD RESISTANCE
(HEADPHONE MODE)
MAX9791 toc25
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
10
50
150
250
0
100
200
1100
f = 1kHz
THD+N = 10%
THD+N = 1%
Typical Operating Characteristics (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.) HEADPHONE
MAX9791/MAX9792
HEADPHONE OUTPUT POWER
vs. HPVDD
MAX9791 toc29
HPVDD (V)
HEADPHONE OUTPUT POWER (mW)
5.04.54.03.53.0
50
100
150
200
250
0
2.5 5.5
THD+N = 1%
f = 1kHz
RL = 32Ω
RL = 16Ω
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________
11
OUTPUT POWER vs. LOAD RESISTANCE
(HEADPHONE MODE)
MAX9791 toc26
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
100
50
70
90
0
60
80
10
30
20
40
10 1000
VHPVDD = 3V
f = 1kHz
THD+N = 10%
THD+N = 1%
POWER DISSIPATION vs. OUTPUT POWER
(HEADPHONE MODE)
MAX9791 toc27
PER CHANNEL OUTPUT POWER (mW)
POWER DISSIPATION PER CHANNEL (mW)
50 100 150
200
250
300
50
100
150
350
400
0
0 20025 75 125 175
RL = 32Ω
RL = 16Ω
POWER DISSIPATION vs. OUTPUT POWER
(HEADPHONE MODE)
MAX9791 toc28
PER CHANNEL OUTPUT POWER (mW)
POWER DISSIPATION PER CHANNEL (mW)
20
100
150
200
50
250
300
0
01008040 60
RL = 32Ω
VHPVDD = 3V RL = 16Ω
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY (HEADPHONE MODE)
MAX9791 toc30
FREQUENCY (kHz)
PSRR (dB)
0.1 1 10
-90
-80
-110
-100
-50
-40
-30
-70
-60
-20
-10
0
-120
0.01 100
VRIPPLE = 200mVP-P
RL = 32Ω
LEFT
RIGHT
CROSSTALK vs. FREQUENCY
(HEADPHONE MODE)
MAX9791 toc31
FREQUENCY (kHz)
CROSSTALK (dB)
0.1 1 10
-90
-80
-50
-40
-30
-70
-60
-20
-100
0.01 100
RIGHT TO LEFT
COM AND SENSE
DISABLED
RIGHT TO LEFT
COM AND SENSE
DISABLED
LEFT TO RIGHT
COM AND SENSE
RL = 32Ω
FS = 300mVRMS
VIN = -20dBFS
RIGHT TO LEFT
COM AND SENSE
Typical Operating Characteristics (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.) HEADPHONE
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
12 ______________________________________________________________________________________
OUTPUT FREQUENCY SPECTRUM
(HEADPHONE MODE)
MAX9791 toc32
FREQUENCY (kHz)
OUTPUT FREQUENCY SPECTRUM (dB)
51015
-120
-100
-40
-20
0
-80
-60
-140
020
RIGHT AND LEFT
FS = 707mVRMS
VIN = -60dBFS
RL = 32Ω
MAX9791 toc33
HP_EN
2V/div
HP_
500mV/div
200µs/div
STARTUP WAVEFORM
MAX9791 toc34
HP_EN
2V/div
HP_
500mV/div
200µs/div
SHUTDOWN WAVEFORM
-130
-90
-110
-50
-70
-30
-10
500 15001000 2000 2500 3000
HEADPHONE RF IMMUNITY
vs. FREQUENCY
MAX9791 toc35
FREQUENCY (MHz)
AMPLITUDE (dBV)
LEFT
RIGHT
RL = 32Ω
HEADPHONE
Typical Operating Characteristics (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.)
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________
13
TOTAL HARMONIC DISTORTION + NOISE
vs. FREQUENCY (HEADPHONE MODE)
MAX9791 toc36
FREQUENCY (kHz)
THD+N (dBFS)
0.1 1 10
-90
-100
-80
-50
-40
-30
-70
-60
-20
-10
0
-110
0.01 100
RL = 10kΩ
VIN = -3dBFS
FS = 707mVRMS FS = 1VRMS
TOTAL HARMONIC DISTORTION + NOISE
vs. FREQUENCY (HEADPHONE MODE)
MAX9791 toc37
FREQUENCY (kHz)
THD+N (dBFS)
0.1 1 10
-90
-100
-80
-50
-40
-30
-70
-60
-20
-10
0
-110
0.01 100
VHPVDD = 3V
RL = 10kΩ
VIN = -3dBFS
FS = 707mVRMS FS = 1VRMS
TOTAL HARMONIC DISTORTION + NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
MAX9791 toc38
OUTPUT POWER (mW)
THD+N (%)
1.0 2.0 3.0
0.001
0.01
0.1
1
10
100
0.0001
04.00.5 1.5 2.5 3.5
RL = 10kΩ
f = 6kHz
f = 1kHz
f = 100Hz
TOTAL HARMONIC DISTORTION + NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
MAX9791 toc39
OUTPUT POWER (mW)
THD+N (%)
2.01.51.0
0.001
0.01
0.1
1
10
100
0.0001
03.02.50.5
VHPVDD = 3V
RL = 10kΩ
f = 6kHz
f = 1kHz
f = 100Hz
CROSSTALK vs. FREQUENCY
(HEADPHONE MODE)
MAX9791 toc40
FREQUENCY (kHz)
CROSSTALK (dB)
0.1 1 10
-90
-80
-110
-100
-50
-40
-30
-70
-60
-20
-120
0.01 100
LEFT TO RIGHT
COM AND SENSE
RL = 10kΩ
FS = 707mVRMS
VIN = -20dBFS
RIGHT TO LEFT
COM AND SENSE
OUTPUT FREQUENCY SPECTRUM
(HEADPHONE MODE)
MAX9791 toc41
FREQUENCY (kHz)
OUTPUT FREQUENCY SPECTRUM (dB)
51015
-120
-100
-40
-20
0
-80
-60
-140
020
RIGHT AND LEFT
RL = 10kΩ
FS = 300mVRMS
VIN = -60dBFS
Typical Operating Characteristics (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.)
LINE OUT
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
14 ______________________________________________________________________________________
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9791 toc42
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
4.75 5.00
0
5
10
15
20
-5
4.50 5.505.25
LDO_EN = 1, VLDO = 3.3V OR 4.75V
SPKR_EN = 1
HP_EN = 0
SPKR_EN = 0
HP_EN = 1
SPKR_EN = 0
HP_EN = 0
SPKR_EN = 1
HP_EN = 1
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9791 toc42a
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
5.04.54.03.53.0
0
5
10
15
20
-5
2.5 5.5
LDO_EN = 1
VLDO_OUT = 1.8V
SPKR_EN = 1
SPKR_EN = 1
SPKR_EN = 0
SPKR_EN = 0
SHUTDOWN CURRENT vs. SUPPLY VOLTAGE
MAX9791 toc43
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT (µA)
5.04.53.0 3.5 4.0
1
2
3
4
5
6
7
8
0
2.5 5.5
SPKR_EN = 1
HP_EN = 0
LDO_EN = 0
Typical Operating Characteristics (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.)
GENERAL
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________
15
LDO OUTPUT ACCURACY
vs. LOAD CURRENT
MAX9791 toc44
LOAD CURRENT (mA)
LDO OUTPUT ACCURACY (%)
12575
-1.0
-1.5
0
0.5
1.0
-0.5
1.5
2.0
-2.0
0 15025 10050
LDO OUTPUT ACCURACY
vs. AMPLIFIER OUTPUT POWER
MAX9791 toc45
AMPLIFIER OUTPUT POWER (mW)
LDO OUTPUT ACCURACY (%)
300
0.04
0.03
0.02
0.01
0.06
0.07
0.08
0.05
0.09
0.10
0
0 15001200600 900
LDO OUTPUT ACCURACY
vs. TEMPERATURE
MAX9791 toc46
TEMPERATURE (°C)
LDO OUTPUT ACCURACY (%)
603510-15
-0.5
0
0.5
1.0
-1.0
-40 85
VLDO_OUT = 3.3V
VLDO_OUT = 1.8V
VLDO_OUT = 4.75V
0
100
50
200
150
250
300
0 100 15050 200 250 300
LDO DROPOUT VOLTAGE vs. LOAD
MAX9791 toc47
ILOAD (mA)
LDO DROPOUT VOLTAGE (mV)
LDO_OUT = 4.75V
LDO POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX9791 toc48
FREQUENCY (kHz)
PSRR (dB)
1010.1
-80
-60
-40
-20
0
20
40
-100
0.01 100
VRIPPLE = 200mVP-P
ILOAD = 10mA
VLDO_OUT = 3.3V
VLDO_OUT = 1.8V
VLDO_OUT = 4.75V
LDO OUTPUT NOISE
MAX9791 toc49
FREQUENCY (kHz)
LDO OUTPUT NOISE (µV)
1010.1
75
100
125
150
175
200
50
0.01 100
CLOAD = 2 x 1µF
ILOAD = 120mA
Typical Operating Characteristics (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.)
LDO
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
16 ______________________________________________________________________________________
1.00ms/div
LINE-TRANSIENT RESPONSE
CH1 LOW
4.560V
CH1 HIGH
5.500V
CH2 HIGH
1.000mV
CH2 LOW
800.0µV
MAX9791 toc50
100ms/div
LOAD-TRANSIENT RESPONSE
ILDO_OUT
50mA/div
MAX9791 toc51
AC-COUPLED
VLDO_OUT
10mV/div
200µs/div
SHUTDOWN RESPONSE
LDO_EN
2V/div
MAX9791 toc52
VLDO_EN
2V/div
CROSSTALK vs. FREQUENCY
SPEAKER TO LDO
MAX9791 toc53
FREQUENCY (kHz)
CROSSTALK (dB)
1010.1
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-130
0.01 100
BOTH SPEAKERS WITH SIGNAL
PSPKR = 1.2W
RLSPKR = 8W
ILDO = 10mA
LEFT CHANNEL TO LDO
RIGHT CHANNEL TO LDO
Typical Operating Characteristics (continued)
(VAVDD = VPVDD = VHPVDD = 5V, VGND = VPGND = VCPGND = 0, ILDO_OUT = 0, CLDO = 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-
erwise specified. RIN1 = 20kΩ(AVSPKR = 12dB), RIN2 = 40.2kΩ(AVHP = 0dB), CIN1 = 470nF, CIN2 = CCOM = 1µF, measurement BW
= 20kHz AES17, TA= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,
HP_EN = 1.)
LDO
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________ 17
MAX9791 Pin Description
PIN NAME FUNCTION
1 SPKR_INL Left-Channel Speaker Amplifier Input
2 HP_INR Right-Channel Headphone Amplifier Input
3 HP_INL Left-Channel Headphone Amplifier Input
4 COM Common-Mode Voltage Sense Input
5 GND Signal Ground. Star connect to PGND.
6 LDO_OUT
LDO Output. Bypass the MAX9791A/MAX9791B with two 1µF ceramic low ESR capacitors to GND.
Bypass the MAX9791C with two 2µs ceramic low ESR capacitors to GND.
7 AVDD Positive Power-Supply and LDO Input. Bypass with a 0.1µF and two 1µF capacitors to GND.
8 LDO_EN LDO Enable. Connect LDO_EN to AVDD to enable the LDO.
9 HPR Right-Channel Headphone Amplifier Output
10 HPL Left-Channel Headphone Amplifier Output
11 SENSE Headphone Ground Sense
12 CPVSS Headphone Amplifier Negative Power Supply. Connect a 1µF capacitor between CPVSS and PGND.
13 C1N Charge-Pump Flying Capacitor Negative Terminal. Connect a 1µF capacitor between C1P and C1N.
14 CPGND Charge-Pump Ground. Connect directly to PGND plane.
15 C1P Charge-Pump Flying Capacitor Positive Terminal. Connect a 1µF capacitor between C1P and C1N.
16 HPVDD Headphone Amplifier Positive Power Supply. Connect a 10µF capacitor between HPVDD and PGND.
17, 26 PVDD Speaker Amplifier Power-Supply Input. Bypass with a 0.1µF capacitor to PGND.
18 OUTL- Left-Channel Speaker Amplifier Output, Negative Phase
19 OUTL+ Left-Channel Speaker Amplifier Output, Positive Phase
20, 23 PGND Power Ground. Star connect to GND.
21 BEEP PC Beep Input. Connect to GND if beep detection function is disabled.
22 HP_EN Active-High Headphone Amplifier Enable
24 OUTR+ Right-Channel Speaker Amplifier Output, Positive Phase
25 OUTR- Right-Channel Speaker Amplifier Output, Negative Phase
27 SPKR_EN Active-Low Speaker Amplifier Enable
28 SPKR_INR Right-Channel Speaker Amplifier Input
— EP Exposed Pad. Connect to GND.
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
18 ______________________________________________________________________________________
Detailed Description
The MAX9791 combines a stereo 2W Class D power
amplifier, a stereo 175mW DirectDrive headphone
amplifier, and a 120mA LDO linear regulator in a single
device. The MAX9792 combines a mono 3W Class D
power amplifier, a stereo 175mW DirectDrive head-
phone amplifier, and a 120mA LDO linear regulator in a
single device.
The MAX9791/MAX9792 feature wake-on-beep detec-
tion, comprehensive click-and-pop suppression, low-
power shutdown mode, and excellent RF immunity.
These devices incorporate an integrated LDO that
serves as a clean power supply for CODEC or other cir-
cuits. The MAX9791/MAX9792 are Windows Vista
Premium compliant. See Table 1 for a comparison of the
Windows Vista Premium specifications and MAX9791/
MAX9792 specifications.
The MAX9791/MAX9792 feature spread-spectrum mod-
ulation and active emission limiting circuitry that offers
significant improvements to switch-mode amplifier tech-
nology. These devices offer Class AB performance with
Class D efficiency in a minimal board-space solution.
The headphone amplifiers use Maxim’s DirectDrive
architecture to eliminate the bulky output DC-blocking
capacitors required by traditional headphone ampli-
fiers. A charge pump inverts the positive supply
(HPVDD) to create a negative supply (CPVSS). The
headphone amplifiers operate from these bipolar sup-
plies with their outputs biased about GND. The bene-
fit of the GND bias is that the amplifier outputs no
longer have a DC component (typically VDD/2). This
feature eliminates the large DC-blocking capacitors
required with conventional headphone amplifiers to
MAX9792 Pin Description
PIN NAME FUNCTION
1, 5 GND Signal Ground. Star connect to PGND.
2 HP_INR Right-Channel Headphone Amplifier Input
3 HP_INL Left-Channel Headphone Amplifier Input
4 COM Common-Mode Voltage Sense Input
6 LDO_OUT LDO Output. Bypass with two 1µF ceramic low ESR capacitors to GND.
7 AVDD Positive Power Supply and LDO Input. Bypass with a 0.1µF and two 1µF capacitors to GND.
8 LDO_EN LDO Enable. Connect LDO_EN to AVDD to enable the LDO.
9 HPR Right-Channel Headphone Amplifier Output
10 HPL Left-Channel Headphone Amplifier Output
11 SENSE Headphone Ground Sense
12 CPVSS Headphone Amplifier Negative Power Supply. Connect a 1µF capacitor between CPVSS and PGND.
13 C1N Charge-Pump Flying Capacitor Negative Terminal. Connect a 1µF capacitor between C1P and C1N.
14 CPGND Charge-Pump Ground. Connect directly to PGND plane.
15 C1P Charge-Pump Flying Capacitor Positive Terminal. Connect a 1µF capacitor between C1P and C1N.
16 HPVDD H ead p hone Am p l i fi er P osi ti ve P ow er S up p l y. C onnect a 10µF cap aci tor b etw een H P V D D and P GN D .
17, 26 PVDD Speaker Amplifier Power-Supply Input. Bypass with a 0.1µF capacitor to PGND.
18, 25 OUT- Speaker Amplifier Output, Negative Phase
19, 24 OUT+ Speaker Amplifier Output, Positive Phase
20, 23 PGND Power Ground. Star connect to GND.
21 BEEP PC Beep Input. Connect to GND if beep detection function is disabled.
22 HP_EN Active-High Headphone Amplifier Enable
27 SPKR_EN Active-Low Speaker Amplifier Enable
28 SPKR_IN Speaker Amplifier Input
— EP Exposed Pad. Connect to GND.
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________ 19
conserve board space and system cost, as well as
improve low-frequency response and distortion.
The MAX9791/MAX9792 amplifiers feature an under-
voltage lockout that prevents operation from an insuffi-
cient power supply and click-and-pop suppression that
eliminates audible transients on startup and shutdown.
The amplifiers include thermal overload and short-cir-
cuit protection.
Class D Speaker Amplifier
The MAX9791/MAX9792 integrate a filterless class D
amplifier that offers much higher efficiency than class AB
amplifiers. The high efficiency of a Class D amplifier is
due to the switching operation of the output stage tran-
sistors. In a Class D 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 I2R 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 power. Under normal operating levels (typical
music reproduction levels), efficiency falls below 45%,
whereas the MAX9791/MAX9792 exhibit 67% efficiency
under the same conditions (Figure 1).
Ultra-Low EMI Filterless Output Stage
In traditional Class D amplifiers, the high dv/dt of the
rising and falling edge transitions resulted in increased
electromagnetic-interference (EMI) emissions, which
required the use of external LC filters or shielding to
meet EN55022B EMI regulation standards. Limiting the
dv/dt normally results in decreased efficiency. Maxim’s
active emissions limiting circuitry actively limits the
dv/dt of the rising and falling edge transitions, providing
reduced EMI emissions while maintaining up to 83%
efficiency.
0
20
10
50
40
30
80
70
60
90
0 0.500.25 0.75 1.00 1.25 1.50
EFFICIENCY vs. IDEAL
CLASS AB EFFICIENCY
OUTPUT POWER (W)
EFFICIENCY (%)
IDEAL CLASS AB
MAX9791
Figure 1. MAX9791 Efficiency vs. Class AB Efficiency
DEVICE TYPE REQUIREMENT
WINDOWS PREMIUM
MOBILE VISTA
SPECIFICATIONS
MAX9791/MAX9792
TYPICAL PERFORMANCE
THD+N ≤ -65dB FS [100Hz, 20kHz] 87dBFS [100Hz, 20kHz]
Dynamic range with signal
present
≤ -80dBV, A-weighted [20Hz,
20kHz] -98.9dB A-weighted [20Hz, 20kHz]
Analog Line-Out Jack
(RL = 10kΩ, FS =
0.707VRMS)
Line output crosstalk ≤ -50dB [20Hz, 15kHz] 64dB [20Hz, 15kHz]
THD+N ≤ -45dB FS [100Hz, 20kHz] 82dBFS [100Hz, 20kHz]
Dynamic range with signal
present
≤ -60dBV, A-weighted [20Hz,
20kHz] -91.5dB A-weighted [20Hz, 20kHz]
Analog Headphone-Out
Jack (RL = 32Ω, FS =
0.300VRMS)Headphone output
crosstalk ≤ -50dB [20Hz, 15kHz] 64dB [20Hz, 15kHz]
Table 1. Windows Premium Mobile Vista Specifications vs. MAX9791/MAX9792
Specifications
Note: THD+N, dynamic range with signal present, and crosstalk should be measured in accordance with AES17 audio measure-
ments standards.
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
20 ______________________________________________________________________________________
In addition to active emission limiting, the MAX9791/
MAX9792 feature spread-spectrum modulation that flat-
tens the wideband spectral components. 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
).
In spread-spectrum modulation mode, the switching fre-
quency varies randomly by ±15kHz around the center
frequency (530kHz). The effect is to reduce the peak
energy at harmonics of the switching frequency. Above
10MHz, the wideband spectrum looks like noise for EMI
purposes (see Figure 2).
Speaker Current Limit
When the output current of the speaker amplifier
exceeds the current limit (2A, typ) the MAX9791/
MAX9792 disable the outputs for approximately 100µs.
At the end of 100µs, the outputs are re-enabled. If the
fault condition still exists, the MAX9791/MAX9792 con-
tinue to disable and re-enable the outputs until the fault
condition is removed.
DirectDrive Headphone Amplifier
Traditional single-supply headphone amplifiers bias the
outputs at a nominal DC voltage (typically half the sup-
ply). Large coupling capacitors are needed to block
this DC bias from the headphone. Without these capac-
itors, a significant amount of DC current flows to the
headphone, resulting in unnecessary power dissipation
and possible damage to both headphone and head-
phone amplifier.
Maxim’s DirectDrive architecture uses a charge pump
to create an internal negative supply voltage. This
allows the headphone outputs of the MAX9791/
MAX9792 to be biased at GND while operating from a
single supply (Figure 3). Without a DC component,
there is no need for the large DC-blocking capacitors.
Instead of two large (220µF, typ) capacitors, the
MAX9791/MAX9792 charge pump requires two small
1µF ceramic capacitors, conserving board space,
reducing cost, and improving the frequency response
of the headphone amplifier.
The MAX9791/MAX9792 feature a low-noise charge
pump. The nominal switching frequency of 530kHz is
well beyond the audio range, and thus does not inter-
fere with audio signals. The switch drivers feature a
controlled switching speed that minimizes noise gener-
ated by turn-on and turn-off transients. By limiting the
switching speed of the charge pump, the di/dt noise
caused by the parasitic trace inductance is minimized.
CLASS D EMI PLOT
FREQUENCY (MHz)
AMPLITUDE (dBµV/m)
100
10
15
20
25
30
35
40
5
30 1000
EN55022B LIMIT
Figure 2. EMI with 30cm of Speaker Cable
VDD
VDD/2
GND
CONVENTIONAL AMPLIFIER BIASING SCHEME
DirectDrive AMPLIFIER BIASING SCHEME
+VDD
GND
-VDD
VOUT
VOUT
Figure 3. Traditional Amplifier Output vs. MAX9791/MAX9792
DirectDrive Output
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________ 21
Common-Mode Sense
Windows Vista-compliant platforms are restricted to only
115mΩof ground return impedance. If the headphone
jack ground is connected close to the audio device
ground using a solid ground plane, the return path resis-
tance can be quite low. However, it is often necessary to
locate some jacks far from the audio device. The
MAX9791/MAX9792 COM and SENSE inputs allow the
headphone jack to be placed further away from the
device without degrading crosstalk performance.
The MAX9791/MAX9792 SENSE and COM inputs sense
and correct for the difference between the headphone
return and device ground. When using common-mode
sense, connect COM through a resistor to GND of the
device (Figure 4). For optimum common-mode rejec-
tion, use the same value resistors for RIN2 and RCOM.
To improve AC CMRR, add a capacitor equal to CIN2
between GND and RCOM.
Configuring SENSE and COM in this way improves sys-
tem crosstalk performance by reducing the negative
effects of the headphone jack ground return resistance.
The headphone amplifier output impedance, trace
resistance, and contact resistance of the jack are
grouped together to represent the source resistance,
RS. The resistance between the load and the sleeve,
the sleeve contact resistance, and the system ground
return resistance are grouped together to represent the
ground resistance, RG.
Assuming a typical source resistance of 5Ω, the ground
return impedance would need to be limited to 115mΩ
to meet Windows Vista’s crosstalk specification of 50dB
(Figure 5). This is further complicated by the fact that
the impedance of the sleeve connection in the 3.5mm
stereo jack can make up 30mΩ–90mΩalone.
The MAX9791/MAX9792 COM and SENSE inputs
reduce crosstalk performance by eliminating effects of
28.5mΩof ground return path resistance. If ground
sensing is not required, connect COM directly to GND
and leave SENSE unconnected (Figure 6).
Wake-on-Beep
The MAX9791/MAX9792 beep-detection circuit wakes
up the device (speaker and headphone amplifiers)
once a qualified beep signal is detected at BEEP and
the LDO is enabled. The amplifier wake command from
the beep-detection circuit overrides the logic signal
applied at HP_EN and SPKR_EN.
Crosstalk in dB R
RR
G
LS
=+
⎛
⎝
⎜⎞
⎠
⎟
20 log
RIN2
RFHP
RFHP
RFHP
COM
HP_INL
HPL
RCOM
SENSE
RIN2
HP_INR
HPR
CIN2
CCOM
CIN2
Figure 4. Connecting COM for Ground Sense
-80
-75
-70
-65
-60
-55
-50
-45
-40
0 0.0500.025 0.075 0.100 0.125 0.150
CROSSTALK
vs. GROUND RESISTANCE (RG)
RG (Ω)
CROSSTALK (dB)
RS = 5Ω
RL = 32Ω
Figure 5. Crosstalk vs. Ground Resistance
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
22 ______________________________________________________________________________________
A qualified BEEP signal consists of a 3.3V typical,
215Hz minimum signal that is present at BEEP for four
consecutive cycles. Once the first rising edge transition
is detected at BEEP, the beep circuit wakes up and
begins counting the beep cycles. Once four consecu-
tive cycles of a qualified beep signal are counted, the
device (speaker and headphone amplifiers) enables
within 400µs. If the first rising edge is not followed by
three consecutive rising edges within 16ms, the device
remains shutdown (i.e., glitch protection).
The device (speaker and headphone amplifiers) returns
to its programmed logic state once 246ms has elapsed
from the time the last rising edge was detected. This
246ms amplifier hold time ensures complete beep pro-
files are passed to the amplifier outputs (Figure 7).
Ground BEEP when the wake-on-beep feature is not
used. Do not leave BEEP unconnected.
Low-Dropout Linear Regulator
The LDO regulator can be used to provide a clean
power supply to a CODEC or other circuitry. The LDO
can be enabled independently of the audio amplifiers.
Set LDO_EN = AVDD to enable the LDO or set LDO_EN
= GND to disable the LDO. The LDO can provide up to
120mA of continuous current.
Speaker and Headphone Amplifier Enable
The MAX9791/MAX9792 feature control inputs for the
independent enabling of the speaker and headphone
amplifiers, allowing both to be active simultaneously
if required. Driving SPKR_EN high disables the speaker
amplifiers. Driving HP_EN low independently disables
the headphone amplifiers. For applications that
require only one of the amplifiers to be on at a given
time, connect SPKR_EN and HP_EN together, allowing
a single logic voltage to enable either the speaker or
the headphone amplifier as shown in Figure 8.
Shutdown
The MAX9791/MAX9792 feature a low-power shutdown
mode, drawing 3.3µA of supply current. By disabling
the speaker, headphone amplifiers, and the LDO, the
MAX9791/MAX9792 enter low-power shutdown mode.
Set SPKR_EN to AVDD and HP_EN and LDO_EN to
GND to disable the speaker amplifiers, headphone
amplifiers, and LDO, respectively.
CROSSTALK vs. FREQUENCY
(HEADPHONE MODE)
FREQUENCY (kHz)
CROSSTALK (dB)
1010.1
-90
-80
-70
-60
-50
-40
-30
-20
-100
0.01 100
RL = 32Ω
FS = 300mVRMS
VOUT = -20dBFS
LEFT TO RIGHT
COM AND SENSE
RIGHT TO LEFT
COM AND SENSE
LEFT TO RIGHT
COM AND SENSE
DISABLED
RIGHT TO LEFT
COM AND SENSE
DISABLED
Figure 6. MAX9791/MAX9792 COM and SENSE Inputs Reduce
Crosstalk
1234
BEEP
SPKR AND HP
AMPS ENABLE
400µs
240ms
16ms
Figure 7. Qualified BEEP Signal Timing
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________ 23
Click-and-Pop Suppression
The MAX9791/MAX9792 feature a common-mode bias
voltage of 0V. A 0V BIAS allows the MAX9791/MAX9792
to quickly turn on/off with no resulting clicks and pops.
With the HDA CODEC outputs biased and the
MAX9791/MAX9792 inputs sitting as 0V in shutdown
and normal operation, the RIN x CIN time constant is
eliminated.
Speaker Amplifier
The MAX9791/MAX9792 speaker amplifiers feature
Maxim’s comprehensive, industry leading click-and-
pop suppression. During startup and shutdown, the
click-and-pop suppression circuitry eliminates any
audible transient sources internal to the device.
Headphone Amplifier
In conventional single-supply headphone amplifiers,
the output-coupling capacitor is a major contributor of
audible clicks and pops. Upon startup, the amplifier
charges the coupling capacitor to its bias voltage, typi-
cally VDD/2. During shutdown, the capacitor is dis-
charged to GND; a DC shift across the capacitor
results, which in turn appears as an audible transient at
the speaker. Because the MAX9791/MAX9792 do not
require output-coupling capacitors, no audible transient
occurs.
The MAX9791/MAX9792 headphone amplifiers feature
extensive click-and-pop suppression that eliminates
any audible transient sources internal to the device.
Applications Information
Filterless Class D Operation
Traditional Class D amplifiers require an output filter to
recover the audio signal from the amplifier’s output. The
filters add cost and size and can decrease efficiency
and THD+N performance. The traditional PWM scheme
uses large differential output swings (2 x PVDD peak-
to-peak) causing large ripple currents. Any parasitic
resistance in the filter components results in a loss of
power, lowering the efficiency.
The MAX9791/MAX9792 do not require an output filter.
The devices rely on the inherent inductance of the speak-
er 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, and more efficient solution.
Because the frequency of the MAX9791/MAX9792 out-
put is well beyond the bandwidth of most speakers,
voice coil movement due to the square-wave frequency
is very small. For optimum results, use a speaker with a
series inductance > 10µH. Typical 8Ωspeakers exhibit
series inductances in the 20µH to 100µH range.
MAX9791
MAX9792
SPKR_EN
SINGLE
CONTROL
HP_EN
Figure 8. Enabling Either the Speaker or Headphone Amplifier
with a Single Control Pin
MAX9791
SPKR_IN_
RIN1
OUT_+
OUT_-
MONO
CLASS D
AMPLIFIER
RFB
20kΩ
CIN1
Figure 9. Setting Speaker Amplifier Gain
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
24 ______________________________________________________________________________________
Setting Speaker Amplifier Gain
External input resistors in conjunction with the internal
feedback resistors (RFSPKR) set the speaker amplifier
gain of the MAX9791/MAX9792. Set gain by using
resistor RIN1 as follows (Figure 9):
where AVSPKR is the desired voltage gain. An RIN1 of
20kΩyields a gain of 4V/V, or 12dB.
Component Selection
Optional Ferrite Bead Filter
In applications where speaker leads exceed 15cm, use
a filter constructed from a ferrite bead and a capacitor
to ground (Figure 10) to provide additional EMI sup-
pression. Use a ferrite bead with low DC resistance,
high frequency (> 1.2MHz) impedance of 100Ωto
600Ω, and rated for at least 1A. The capacitor value
varies based on the ferrite bead chosen and the actual
speaker lead length. Select the capacitor value based
on EMI performance.
Output Power (Headphone Amplifier)
The headphone amplifiers are specified for the worst-
case scenario when both inputs are in phase. Under
this condition, the drivers simultaneously draw current
from the charge pump, leading to a slight loss in head-
room of CPVSS. In typical stereo audio applications, the
left and right signals have differences in both magni-
tude and phase, subsequently leading to an increase in
the maximum attainable output power. Figure 11 shows
the two extreme cases for in and out of phase. In most
cases, the available power lies between these
extremes.
Headphone Amplifier Gain
Gain-Setting Resistors
External input resistors in conjunction with the internal
feedback resistors (RFHP) set the headphone amplifier
gain of the MAX9791/MAX9792. Set gain by using
resistor RIN2 (Figure 4) as follows:
where AVHP is the desired voltage gain. An RIN2 of
40.2kΩyields a gain of 1V/V, or 0dB.
Power Supplies
The MAX9791/MAX9792 speaker amplifiers are pow-
ered from PVDD with a range from 2.7V to 5.5V. The
headphone amplifiers are powered from HPVDD and
CPVSS. HPVDD is the positive supply of the headphone
amplifiers and charge pump ranging from 2.7V to 5.5V.
CPVSS is the negative supply of the headphone ampli-
fiers. The charge pump inverts the voltage at HPVDD,
and the resulting voltage appears at CPVSS. AVDD
powers the LDO and the remainder of the device.
AVDD and PVDD must be tied together. If LDO is
enabled, set AVDD and PVDD as specified in the Line
Regulation row of the
Electrical Characteristics
table.
Ak
RVV
VHP IN
=⎛
⎝
⎜⎞
⎠
⎟
-40 2
2
./
Ω
Ak
RVV
VSPKR IN
=⎛
⎝
⎜⎞
⎠
⎟
-4 20
1
Ω/
MAX9791
MAX9792
L1*
L2*
330pF 330pF
*L1 = L2 = WÜRTH 742792040
Figure 10. Optional Ferrite Bead Filter
TOTAL HARMONIC DISTORTION + NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
OUTPUT POWER (mW)
THD+N (%)
20015010050
0.01
0.1
1
10
100
0.001
0 250
RL = 32Ω
OUT OF PHASE
IN PHASE
Figure 11. Output Power vs. Supply Voltage with Inputs In/Out
of Phase; 32ΩLoad Conditions and 3.5dB Gain
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________ 25
Component Selection
Speaker Amplifier Power-Supply Input (PVDD)
PVDD powers the speaker amplifiers. PVDD ranges
from 2.7V to 5.5V. AVDD and PVDD must be tied
together. If LDO is enabled, set AVDD and PVDD as
specified in the Line Regulation row of the
Electrical
Characteristics
table. Bypass PVDD with a 0.1µF
capacitor to PGND. Apply additional bulk capacitance
at the device if long input traces between PVDD and
the power source are used.
Headphone Amplifier Power-Supply Input
(HPVDD and CPVSS)
The headphone amplifiers are powered from HPVDD
and CPVSS. HPVDD is the positive supply of the head-
phone amplifiers and ranges from 2.7V to 5.5V. Bypass
HPVDD with a 10µF capacitor to PGND. CPVSS is the
negative supply of the headphone amplifiers. Bypass
CPVSS with a 1µF capacitor to PGND. The charge
pump inverts the voltage at HPVDD, and the resulting
voltage appears at CPVSS. A 1µF capacitor should be
connected between C1N and C1P.
Positive Power Supply and LDO Input (AVDD)
The internal LDO and the remainder of the device are
powered by AVDD. AVDD ranges from 2.7V to 5.5V.
AVDD and PVDD must be tied together. If LDO is
enabled, set AVDD and PVDD as specified in LDO line
regulation. Bypass AVDD with a 0.1µF capacitor to
GND and two 1µF capacitors to GND. Note additional
bulk capacitance is required at the device if long input
traces between AVDD and the power source are used.
Input Filtering
The input capacitor (CIN_), in conjunction with the ampli-
fier input resistance (RIN_), forms a highpass filter that
removes the DC bias from the incoming signal. The AC-
coupling capacitor allows the amplifier to bias the signal
to an optimum DC level. Assuming zero source imped-
ance, the -3dB point of the highpass filter is given by:
RIN_ is the amplifier’s external input resistance value.
Choose CIN_ such that f-3dB is well below the lowest
frequency of interest. Setting f-3dB too high affects
the amplifier’s low frequency response. Use capaci-
tors with adequately low-voltage coefficients (see
Figure 12). Capacitors with higher voltage coeffi-
cients, such as ceramics, result in increased distor-
tion at low frequencies.
Charge-Pump Capacitor Selection
Use capacitors with an ESR less than 100mΩfor opti-
mum performance. Low ESR ceramic capacitors mini-
mize the output resistance of the charge pump. For
best performance over the extended temperature
range, select capacitors with an X7R dielectric.
Flying Capacitor (C1)
The value of the flying capacitor (C1) affects the load
regulation and output resistance of the charge pump. A
C1 value that is too small degrades the device’s ability
to provide sufficient current drive, which leads to a loss
of output voltage. Connect a 1µF capacitor between
C1P and C1N.
fRC
dB IN IN
-3
1
2
=π__
INPUT COUPLING CAPACITOR-INDUCED THD+N
vs. FREQUENCY (HEADPHONE MODE)
FREQUENCY (kHz)
THD+N (dBFS)
100
-90
-80
-70
-60
-50
-100
10 1000
0603 10V X5R 10% 1µF
0805 50V X7R 10% 1µF
VOUT - -3dBFS
FS = 1VRMS
RL =32Ω
0603 10V X7R 10% 1µF
0402 6.3V X5R 10% 1µF
Figure 12. Input Coupling Capacitor-Induced THD+N vs.
Frequency
SPEAKER RF IMMUNITY
vs. FREQUENCY
FREQUENCY (MHz)
AMPLITUDE (dBV)
2500200015001000500
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-130
0 3000
RIGHT
LEFT
Figure 13. Speaker RF Immunity
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
26 ______________________________________________________________________________________
Charge-Pump Output Capacitor (C2)
Connect a 1µF capacitor between CPVSS and PGND.
LDO Output Capacitor (CLDO)
Connect 2 x 1µF capacitors between LDO_OUT and
GND for 4.75V and 3.3V LDO options (MAX979_A and
MAX979_B, respectively). Connect two parallel 2µF
capacitors between LDO_OUT and GND for the 1.8V
LDO option (MAX979_C).
Layout and Grounding
Proper layout and grounding are essential for optimum
performance. Use large traces for the power-supply
inputs and amplifier outputs to minimize losses due to
parasitic trace resistance, as well as route heat away
from the device. Good grounding improves audio per-
formance, minimizes crosstalk between channels, and
prevents switching noise from coupling into the audio
signal. Connect PGND and GND together at a single
point on the PCB. Route PGND and all traces that carry
switching transients away from GND, and the traces
and components in the audio signal path.
Connect C2 to the PGND plane. Place the charge-
pump capacitors (C1, C2) as close as possible to the
device. Bypass PVDD with a 0.1µF capacitor to PGND.
Place the bypass capacitors as close as possible to the
device.
The MAX9791/MAX9792 is inherently designed for
excellent RF immunity. For best performance, add
ground fills around all signal traces on top or bottom
PCB planes.
Use large, low-resistance output traces. As load imped-
ance decreases, the current drawn from the device out-
puts increase. At higher current, the resistance of the
output traces decrease the power delivered to the load.
For example, if 2W is delivered from the speaker output
to a 4Ωload through a 100mΩtrace, 49mW is wasted
in the trace. If power is delivered through a 10mΩ
trace, only 5mW is wasted in the trace. Large output,
supply, and GND traces also improve the power dissi-
pation of the device.
The MAX9791/MAX9792 thin QFN package features an
exposed thermal pad on its underside. This pad lowers
the package’s thermal resistance by providing a direct
heat conduction path from the die to the printed circuit
board. Connect the exposed thermal pad to GND by
using a large pad and multiple vias to the GND plane.
Chip Information
PROCESS: BiCMOS
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________ 27
MAX9792
SPKR_EN
HP_EN
LDO_EN
BEEP
SPEAKER AND LDO
SUPPLY
2.7V TO 5.5V
HEADPHONE SUPPLY
2.7V TO 5.5V
SPKR_IN
HP_INR
HP_INL
CLASS D
AMP
AVDD
LDO 1.8V OR 4.75V
Simplified Block Diagrams
(continued)
26
27
25
24
10
9
11
HP_INR
COM
GND
LDO_OUT
AVDD
12
SPKR_INL
PGND
OUTL-
PVDD
BEEP
HPVDD
C1P
12
OUTR-
4567
2021 19 17 16 15
PVDD
SPKR_EN
CPVSS
SENSE
HPL
HPR
MAX9791
HP_INL OUTL+
3
18
28 8
SPKR_INR LDO_EN
OUTR+
23 13 C1N
PGND
22 14 CPGND
HP_EN
TQFN
(4mm x 4mm x 0.75mm)
TOP VIEW
+
*EP
*EP = EXPOSED PAD
26
27
25
24
10
9
11
HP_INR
COM
GND
LDO_OUT
AVDD
12
GND
PGND
OUT-
PVDD
BEEP
HPVDD
C1P
12
OUT-
4567
2021 19 17 16 15
PVDD
SPKR_EN
CPVSS
SENSE
HPL
HPR
MAX9792
HP_INL OUT+
3
18
28 8
SPKR_IN LDO_EN
OUT+
23 13 C1N
PGND
22 14 CPGND
HP_EN
TQFN
(4mm x 4mm x 0.75mm)
TOP VIEW
+
*EP = EXPOSED PAD
*EP
Pin Configurations
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
28 ______________________________________________________________________________________
MAX9791A
MAX9791B
LDO_EN 8
HP_INL 3
HP_INR 2
LDO_OUT 6
HP_EN 22
BEEP 21
SPKR_EN 27
STEREO
CLASS D
AMPLIFIER
CONTROL
CHARGE
PUMP
LDO BLOCK
TO HPVDD
TO CPVSS
1
19 OUTL+
OUTL-
OUTR+
OUTR-
HPL
HPR
HPVDD
C1P
C1N
CPGND
18
24
25
10
9
16
15
14
13
12
CPVSS
C2
1.0µF
20, 23
PGNDGND
5
SPKR_INL
SPKR_INR 28
1.0µF
1.0µF
2.7V TO 5.5V
2.7V TO 5.5V
TO CODEC
NOTE: LOGIC PINS CONFIGURED FOR:
LDO_EN = 1, LDO ENABLED
SPKR_EN = 0, SPEAKER AMPLIFIERS ENABLED
HP_EN = 1, HEADPHONE AMPLIFIER ENABLED
C1
1.0µF
0.1µF
PVDD
17, 26
2.7V TO 5.5V
AVDD
7
0.1µF
1.0µF1.0µF10µF
C3
10µF
RIN3
RIN1
CIN3
CIN1
RIN1
CIN1
RIN3
CIN3
RIN2
CIN2
RIN2
CIN2
11 SENSE
40.2kΩ
40.2kΩ
40.2kΩ
TO HPVDD
20kΩ
20kΩ
4
CCOM RCOM
µC BEEP INPUT
COM
MAX9791A/MAX9791B Block Diagram
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________ 29
MAX9791C
LDO_EN 8
HP_INL 3
HP_INR 2
LDO_OUT 6
HP_EN 22
BEEP 21
SPKR_EN 27
STEREO
CLASS D
AMPLIFIER
CONTROL
CHARGE
PUMP
LDO BLOCK
TO HPVDD
TO CPVSS
1
19 OUTL+
OUTL-
OUTR+
OUTR-
HPL
HPR
HPVDD
C1P
C1N
CPGND
18
24
25
10
9
16
15
14
13
12
CPVSS
C2
1.0µF
20, 23
PGNDGND
5
SPKR_INL
SPKR_INR 28
2.0µF
2.0µF
2.7V TO 5.5V
2.7V TO 5.5V
TO CODEC
NOTE: LOGIC PINS CONFIGURED FOR:
LDO_EN = 1, LDO ENABLED
SPKR_EN = 0, SPEAKER AMPLIFIER ENABLED
HP_EN = 1, HEADPHONE AMPLIFIER ENABLED
C1
1.0µF
0.1µF
PVDD
17, 26
2.7V TO 5.5V
AVDD
7
0.1µF
1.0µF1.0µF10µF
C3
10µF
RIN3
RIN1
CIN3
CIN1
RIN1
CIN1
RIN3
CIN3
RIN2
CIN2
RIN2
CIN2
11 SENSE
40.2kΩ
40.2kΩ
40.2kΩ
TO HPVDD
20kΩ
20kΩ
4
CCOM RCOM
µC BEEP INPUT
COM
MAX9791C Block Diagram
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
30 ______________________________________________________________________________________
MAX9792A
LDO_EN 8
HP_INL 3
HP_INR 2
LDO_OUT 6
HP_EN 22
BEEP 21
SPKR_EN 27
MONO
CLASS D
AMPLIFIER
CONTROL
CHARGE
PUMP
LDO BLOCK
TO HPVDD
TO CPVSS
28
19, 24 OUT+
OUT-
HPL
HPR
HPVDD
C1P
C1N
CPGND
18, 25
10
9
16
15
14
13
12
CPVSS
C2
1.0µF
20, 23
PGNDGND
1, 5
SPKR_IN
1.0µF
1.0µF
2.7V TO 5.5V
2.7V TO 5.5V
TO CODEC
NOTE: LOGIC PINS CONFIGURED FOR:
LDO_EN = 1, LDO ENABLED
SPKR_EN = 0, SPEAKER AMPLIFIER ENABLED
HP_EN = 1, HEADPHONE AMPLIFIER ENABLED
C1
1.0µF
C3
10µF
RIN1
CIN1
RIN2
CIN2
RIN2
CIN2
11 SENSE
TO HPVDD
4
CCOM RCOM
µC BEEP INPUT
RIN3
CIN3
20kΩ
40.2kΩ
40.2kΩ
40.2kΩ
COM
0.1µF
PVDD
17, 26
2.7V TO 5.5V
AVDD
7
0.1µF
1.0µF1.0µF10µF
MAX9792A Block Diagram
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________ 31
MAX9792C
LDO_EN 8
HP_INL 3
HP_INR 2
LDO_OUT 6
HP_EN 22
BEEP 21
SPKR_EN 27
MONO
CLASS D
AMPLIFIER
CONTROL
CHARGE
PUMP
LDO BLOCK
TO HPVDD
TO CPVSS
28
19, 24 OUT+
OUT-
HPL
HPR
HPVDD
C1P
C1N
CPGND
18, 25
10
9
16
15
14
13
12
CPVSS
C2
1.0µF
20, 23
PGNDGND
1, 5
SPKR_IN
2.0µF
2.0µF
2.7V TO 5.5V
2.7V TO 5.5V
TO CODEC
NOTE: LOGIC PINS CONFIGURED FOR:
LDO_EN = 1, LDO ENABLED
SPKR_EN = 0, SPEAKER AMPLIFIER ENABLED
HP_EN = 1, HEADPHONE AMPLIFIER ENABLED
C1
1.0µF
C3
10µF
RIN1
CIN1
RIN2
CIN2
RIN2
CIN2
11 SENSE
TO HPVDD
4
CCOM RCOM
µC BEEP INPUT
RIN3
CIN3
20kΩ
40.2kΩ
40.2kΩ
40.2kΩ
COM
0.1µF
PVDD
17, 26
2.7V TO 5.5V
AVDD
7
0.1µF
1.0µF1.0µF10µF
MAX9792C Block Diagram
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
32 ______________________________________________________________________________________
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
28 TQFN-EP T2844-1 21-0139 90-0068
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.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.
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
______________________________________________________________________________________ 33
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.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.
MAX9791/MAX9792
Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers
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.
34
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 11/08 Initial release —
1 6/10 Adding MAX9791C/MAX9792C versions 1–7, 10, 13–16,
19, 21–30
