Rainbow Electronics MAX9792 User Manual

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 regu­lator 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 patented**
DirectDrive headphone amplifier architecture that pro­duces a ground-referenced output from a single supply,
eliminating 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 head­phone amplifier crosstalk by sensing the impedance in
the ground return trace and correcting for it at the out­put 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 con­nected 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 patented

†

spread-spectrum modulation and patented††active
emissions limiting circuitry. Industry-leading click-and­pop suppression eliminates audible transients during
power-up and shutdown cycles.

The MAX9791/MAX9792 wake-on-beep feature wakes
up the speaker and headphone amplifiers when a qual­ified beep signal is detected at the BEEP input.

For maximum flexibility, separate speaker and head­phone 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 avail­able 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

♦ Windows Vista® Premium Compliant
♦ Low EMI Filterless Class D Speaker Amplifiers

Pass EN55022B Emissions Limit with 30cm of
Speaker Cable

♦ 180mW DirectDrive Headphone Amplifier
♦ Excellent RF Immunity
♦ Integrated 120mA LDO
♦ Eliminates Headphone Ground Loop Noise
♦ Wake-on-Beep Function
♦ Click-and-Pop Suppression
♦ Short-Circuit and Thermal-Overload Protection
♦ Thermally 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 0; 11/08

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

Note: All devices are specified over the -40°C to +85°C
extended temperature range.

+

Denotes a lead-free/RoHS-compliant package.

*

EP = Exposed pad.

Windows Vista is a registered trademark of Microsoft Corp.

MAX9791A
MAX9791B

SPKR_EN
HP_EN
LDO_EN
BEEP

SPEAKER SUPPLY

4.5V TO 5.5V

HEADPHONE SUPPLY

2.7V TO 5.5V

LDO

4.5V TO 5.5V

3.3V OR 4.75V

CLASS D

AMP

CLASS D

AMP

Simplified Block Diagrams

Simplified Block Diagrams continued at end of data sheet.

DirectDrive is a registered trademark of Maxim Integrated
Products, Inc.

**

U.S. Patent #7,061,327.

†

U.S. Patent #6,847,257.

††

U.S. Patent #7,190,225.

PART

MAX9791AETI+ Stereo 4.75V 28 TQFN-EP*

MAX9791BETI+ Stereo 3.3V 28 TQFN-EP*

MAX9792AETI+ Mono 4.75V 28 TQFN-EP*

STEREO/

MONO

LDO

OUTPUT

PIN-PACKAGE

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2µF, C1 = C2 = 1µF. RL= ∞, unless other-

wise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, TA= T

MIN

to T

MAX

,

unless otherwise noted. Typical values are at T

A

= +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

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 (T

A

= +70°C)

28-Pin Thin QFN Single-Layer Board (derate 20.8mW/°C

above +70°C)..........................................................1667mW

Junction-to-Ambient Thermal Resistance (θ

JA

)

(Note 2) .....................................................................40°C/W

Junction-to-Case Thermal Resistance (θ

JC

)

(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 (θ

JA

)

(Note 2) .....................................................................35°C/W

Junction-to-Case Thermal Resistance (θ

JC

)

(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

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

.

GENERAL

Supply Voltage

Headphone Supply Voltage V

Undervoltage Lockout UVLO 2.65 V

Quiescent Current

Shutdown Current I

Bias Voltage V

Shutdown to Full Operation t

Overtemperature Threshold +150 °C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

V

AVDD

V

PVDD

HPVDD

I

AVDD

I

PVDD

I

HPVDD

SHDN

BIAS

ON

,

Guaranteed by PSRR test 4.5 5.5 V

Guaranteed by PSRR test 2.7 5.5 V

+

+

HP_INR, HP_INL, SPKR_INR, SPKR_INL 0 V

SPKR_EN HP_EN LDO_EN

1 0 1 250 400 µA

1 1 0 4.4 6 mA

0 0 0 10.5 15 mA

0 1 0 14.4 21 mA

1 0 0 0.1 1 µA

0.4 ms

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2µF, C1 = C2 = 1µF. RL= ∞, unless other-

wise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, TA= T

MIN

to T

MAX

,

unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 3)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SPEAKER AMPLIFIER

Output Power P

Total Harmonic Distortion Plus
Noise

OUT

THD+N

Power-Supply Rejection Ratio PSRR

Feedback Impedance R

Gain A

Output Offset Voltage V

Click-and-Pop Level K

FSKR

V

OS

CP

Signal-to-Noise Ratio SNR

Noise V

N

Crosstalk

THD+N = 1%,
f = 1kHz,

= +25°C

T

A

(Note 4)

THD+N = 10%,
f = 1kHz,
T

= +25°C

A

(Note 4)

RL = 8Ω, P

R

= 4Ω, P

L

V

= V

AVDD

= 500mW, f = 1kHz (Note 4) 0.04

OUT

= 500mW, f = 1kHz (Note 4) 0.03

OUT

= 4.5V to 5.5V, TA = +25°C60 80

PVDD

f = 217Hz, 200mV

f = 1kHz, 200mV

P-P

f = 10kHz, 200mV

Guaranteed by design 20 kΩ

R

= 20kΩ 12 dB

IN1

Measured between OUT_+ and OUT_-,
T

= +25°C

A

RL = 8Ω,
peak voltage,
A-weighted,
32 samples per second
(Notes 4, 5, and 6)

R

= 8Ω

L

= 1.2W fIN = 1kHz,

P

OUT

(Note 4)

A-weighted 38 µV

L to R, R to L, RL = 8Ω, V
100m V

R M S

, f

I N

= 1kH z ( N ote 4)

L to R, R to L, RL = 8Ω, V
100m V

HP to SPKR, R
R

LHP

, f

= 15kH z ( N ote 4)

R M S

I N

LSPKR

= 32Ω, fIN = 1kHz (Note 4)

RL = 4Ω
(MAX9791)

RL = 8Ω
(MAX9791)

= 3Ω

R

L

(MAX9792)

RL = 4Ω
(MAX9791)

RL = 8Ω
(MAX9791)

= 3Ω

R

L

(MAX9792)

P-P

P-P

Into shutdown -52.4

Out of
shutdown

A-weighted 98

20Hz to 20kHz 94

= - 20d BFS =

I N

= - 20d BFS =

I N

= 8Ω, PHP = 20mW,

1.7

1.2

3

W

2.2

1.5

3.7

%

73

75

dB

62

±3 ±10 mV

dBV

-54

dB

RMS

78

70

dB

77

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2µF, C1 = C2 = 1µF. RL= ∞, unless other-

wise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, TA= T

MIN

to T

MAX

,

unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 3)

Class D Switching Frequency f

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SPK

948 1158 kHz

Spread-Spectrum Bandwidth ±15 kHz

Efficiency η P

= 1.5W, fIN = 1kHz, RL = 8Ω (Note 4) 83 %

OUT

HEADPHONE AMPLIFIER

Output Power P

Total Harmonic Distortion Plus
Noise

OUT

THD+N

Power-Supply Rejection Ratio PSRR

Feedback Impedance R

Gain A

Output Offset Voltage V

Click-and-Pop Level K

FHP

V

OS

CP

Signal-to-Noise Ratio SNR

Noise V

Maximum Capacitive Load Drive C

N

L

Crosstalk

THD+N = 1%,
f = 1kHz,
T

= +25°C

A

RL = 32Ω, f

= -3dBFS = 212mV

V

IN

= 6kHz, 20kHz AES17,

IN

RL = 10kΩ, fIN = 6kHz, 20kHz AES17,
V

= -3dBFS = 500mV

IN

RL = 32Ω, P

= 16Ω, P

R

L

V

HPVDD

f = 1kHz, V

f = 10kHz, V

R

IN2

OUT

OUT

= 2.7V to 5.5V, TA = +25°C 70 107

RIPPLE

RIPPLE

= 40.2kΩ 0dB

TA = +25°C ±0.3 ±3 mV

RL = 32Ω,
peak voltage,
A-weighted, 32 samples
per second (Notes 5, 6)

R

= 32Ω, P

L

f

= 1kHz

IN

OUT

A-weighted 8 µV

No sustained oscillations 100 pF

L to R, R to L, f

IN

= 1kHz, COM
and SENSE
connected

L to R, R to L, f

IN

= 15kHz, COM
and SENSE
connected

SPKR to HP, R

= 32Ω, fIN = 1Hz

R

LHP

LSPKR

RL = 16Ω 100

= 32Ω 180

R

L

RMS

RMS

-78

-87

= 100mW, f = 1kHz 0.006

= 75mW, f = 1kHz 0.014

= 200mV

= 200mV

P-P

P-P

91

80

38.2 40.2 42.2 kΩ

Into shutdown -81

= 40mW,

Out of
shutdown

A-weighted 102

-72.5

20Hz to 20kHz 94

RL = 32Ω, VIN =

-20dBFS = 30mV

= 10kΩ, VIN =

R

L

-20dBFS = 0.7mV

RL = 32Ω, VIN =

-20dBFS = 30mV

= 10kΩ, VIN =

R

L

-20dBFS = 70.7mV

= 8Ω, P

SPKR

= 1W,

RMS

RMS

RMS

RMS

82

89

64

70

80

mW

dBFS

%

dB

dBV

dB

RMS

dB

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2µF, C1 = C2 = 1µF. RL= ∞, unless other-

wise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, TA= T

MIN

to T

MAX

,

unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 3)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

COM Input Range V

COM

Common-Mode Rejection Ratio CMRR -300mV < V

Inferred from CMRR test -300 +300 mV

< +300mV 60 dB

COM

Slew Rate SR 0.38 V/µs

Charge-Pump Frequency f

OSC

530 kHz

BEEP INPUT (LDO_EN = 1)

Beep Signal Minimum Frequency f

Amplifier Turn-On Time t

Amplifier Hold Time t

HOLDBEEP

BEEP

ONBEEP

Four-cycle count 215 Hz

400 µs

221 246 271 ms

LOW-DROPOUT LINEAR REGULATOR

Regulator Input Voltage Range V

LDO Ground Current I

Output Current I

Current Limit I

Crosstalk

AVDD

LDO

OUT

LIM

Inferred from line regulation,
V

LDO_OUT

= 4.75V

Inferred from load regulation 120 mA

Speaker to LDO, V
f =1kHz, I

LDO_OUT

LDO_OUT

= 10mA, speaker P

= 4.75V,

OUT

4.5 5.5 V

0.25 0.4 mA

300 mA

-80 dB

= 1.2W, RL = 8Ω

Output-Voltage Accuracy

Dropout Voltage V

DO

V

LDO_OUT

V

LDO_OUT

V

LDO_OUT

T

A

= 4.75V ±1.5

= 3.3V ±1.5

I

= 50mA 46

= 4.75V,

= +25°C (Note 7)

OUT

I

= 120mA 106

OUT

Startup Time 30 µs

V

= 4.5V to

Line Regulation

Load Regulation

Ripple Rejection

Output-Voltage Noise

AVDD

5.5V,
I

LDO_OUT

V

LDO_OUT

= 1mA

= 4.75V, 1mA < I

120mA

V
V
I

RIPPLE

LDO_OUT

LDO_OUT

= 200mV

= 4.75V

= 10mA

20Hz to 20kHz, C
I

LDO_OUT

= 120mA

P-P

V

V

,

LDO_OUT

LDO_OUT

= 4.75V -4.8 1.5 +4.8

= 3.3V -4 0.2 +4

LDO_OUT

<

f = 1kHz 56

f = 10kHz 40

LDO_OUT

= 2 x 1µF,

0.22 mV/mA

130 µV

DIGITAL INPUTS (SPKR_EN, HP_EN, LDO_EN, BEEP)

Input-Voltage High V

Input-Voltage Low V

INH

INL

2V

0.4 V

Input Bias Current -1 +1 µA

%

mV

mV/V

dB

RMS

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: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For R

L

= 3Ω, L = 22µH.

For R

L

= 4Ω, L = 33µH. For RL= 8Ω, L = 68µH.

Note 5: Specified at T

A

= +25°C with an 8Ω + 68µH load connected across BTL output for speaker amplifier. Specified at TA= +25°C

with a 32Ω resistive 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 6: Amplifier Inputs AC-coupled to GND.
Note 7: 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
V

IN

= -3dBFS

FS = 707mV

RMS

FS = 1V

RMS

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
V

IN

= -3dBFS

FS = 707mV

RMS

FS = 1V

RMS

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
V

IN

= -3dBFS

FS = 707mV

RMS

FS = 1V

RMS

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
0 2.01.5

RL = 8Ω

f = 6kHz

f = 1kHz

f = 100Hz

Typical Operating Characteristics

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-

erwise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, measurement BW

= 20kHz AES17, T

A

= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,

HP_EN = 1.)

SPEAKER

ELECTRICAL CHARACTERISTICS (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2µF, C1 = C2 = 1µF. RL= ∞, unless other-

wise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, TA= T

MIN

to T

MAX

,

unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 3)

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

_______________________________________________________________________________________

7

Typical Operating Characteristics (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-

erwise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, measurement BW

= 20kHz AES17, T

A

= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,

HP_EN = 1.)

SPEAKER

OUTPUT POWER vs. LOAD RESISTANCE

(MAX9792 SPEAKER MODE)

5.0

4.5

4.0

3.5

3.0

2.5

2.0

OUTPUT POWER (W)

1.5

1.0

0.5

0

1 100

THD+N = 10%

10

LOAD RESISTANCE (Ω)

EFFICIENCY vs. OUTPUT POWER

(MAX9791 SPEAKER MODE)

100

90

80
70
60
50
40

EFFICIENCY (%)

30
20

10

0

0 1.81.20.3

OUTPUT POWER (W)

f = 1kHz

THD+N = 1%

RL = 8Ω

RL = 4Ω

fIN = 1kHz

1.50.90.6

MAX9791 toc07

OUTPUT POWER (W)

MAX9791 toc10

PSRR (dB)

-100

OUTPUT POWER vs. LOAD RESISTANCE

3.0

2.5

2.0

1.5

1.0

0.5

-10

-20

-30

-40

-50

-60

-70

-80

-90

(MAX9791 SPEAKER MODE)

f = 1kHz

THD+N = 10%

THD+N = 1%

0

1 100

10

LOAD RESISTANCE (Ω)

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY (SPEAKER MODE)

0

V

= 200mV

RIPPLE

RL = 8Ω

0.01 100

P-P

LEFT

0.1 10

1

FREQUENCY (kHz)

RIGHT

EFFICIENCY vs. OUTPUT POWER

(MAX9792 SPEAKER MODE)

110

MAX9791 toc08

100

90
80
70
60
50

EFFICIENCY (%)

40
30
20
10

0

1.0 2.0 3.0

0 4.00.5 1.5 2.5 3.5

OUTPUT POWER (W)

RL = 8Ω

CROSSTALK vs. FREQUENCY

(SPEAKER MODE)

0

FS = 1V

RMS

VIN = -20dBFS

= 8Ω

R

L

RIGHT TO LEFT

LEFT TO RIGHT

0.01 100

0.1 10

1

FREQUENCY (kHz)

MAX9791 toc11

-10

-20

-30

-40

-50

-60

-70

CROSSTALK (dB)

-80

-90

-100

-110

MAX9791 toc09

RL = 3Ω

fIN = 1kHz

MAX9791 toc12

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-

erwise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, measurement BW

= 20kHz AES17, T

A

= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,

HP_EN = 1.)

SPEAKER

SPEAKER STARTUP WAVEFORM

MAX9791 toc13

SPEAKER SHUTDOWN WAVEFORM

MAX9791 toc14

200μs/div

WIDEBAND OUTPUT SPECTRUM

0

-10

-20

-30

-40

-50

-60

-70

-80

OUTPUT AMPLITUDE (dBV)

-90

-100

-110

-120
0 100

(SPEAKER MODE)

RBW = 1kHz
INPUT AC GROUNDED

FREQUENCY (MHz)

101

SPKR_EN
2V/div

SPEAKER OUT

MAX9791 toc15

200μs/div

OUTPUT FREQUENCY SPECTRUM

(SPEAKER MODE)

0

V

= -60dBV

OUT

f = 1kHz

-20

= 8Ω

R

L

UNWEIGHTED

-40

-60

-80

-100

OUTPUT MAGNITUDE (dBV)

-120

-140
120515

10

FREQUENCY (kHz)

SPKR_EN
2V/div

SPEAKER OUT

MAX9791 toc16

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

_______________________________________________________________________________________

9

Typical Operating Characteristics (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-

erwise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, measurement BW

= 20kHz AES17, T

A

= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,

HP_EN = 1.)

HEADPHONE

TOTAL HARMONIC DISTORTION + NOISE

vs. FREQUENCY (HEADPHONE MODE)

-50

RL = 16Ω

= -3dBFS

V

IN

-60

-70

-80

THD+N (dBFS)

-90

-100

0.01 100

FS = 300mV

FS = 1V

RMS

0.1 10

1

FREQUENCY (kHz)

TOTAL HARMONIC DISTORTION + NOISE

vs. FREQUENCY (HEADPHONE MODE)

-50

V

= 3V

HPVDD

= 32Ω

R

L

= -3dBFS

V

IN

-60

RMS

MAX9791 toc17

THD+N (dBFS)

-100

MAX9791 toc20

-50

-60

-70

-80

-90

0.01 100

vs. OUTPUT POWER (HEADPHONE MODE)

100

10

TOTAL HARMONIC DISTORTION + NOISE

vs. FREQUENCY (HEADPHONE MODE)

V

= 3V

HPVDD

= 16Ω

R

L

= -3dBFS

V

IN

FS = 300mV

FS = 1V

0.1 10
FREQUENCY (kHz)

RMS

RMS

1

TOTAL HARMONIC DISTORTION + NOISE

RL = 16Ω

TOTAL HARMONIC DISTORTION + NOISE

vs. FREQUENCY (HEADPHONE MODE)

-50

RL = 32Ω

= -3dBFS

V

MAX9791 toc18

IN

-60

-70

FS = 300mV

RMS

-80

THD+N (dBFS)

-90

-100

0.01 100

FS = 1V

RMS

0.1 10

1

FREQUENCY (kHz)

TOTAL HARMONIC DISTORTION + NOISE

vs. OUTPUT POWER (HEADPHONE MODE)

100

RL = 32Ω

MAX9791 toc21

10

MAX9791 toc19

MAX9791 toc22

-70

FS = 300mV

-80

THD+N (dBFS)

-90

-100

0.01 100

RMS

FS = 1V

RMS

0.1 10

1

FREQUENCY (kHz)

TOTAL HARMONIC DISTORTION + NOISE

vs. OUTPUT POWER (HEADPHONE MODE)

100

V

= 3V

HPVDD

= 16Ω

R

L

10

1

f = 100Hz

THD+N (%)

0.1

f = 1kHz

0.01

0.001
05040 90

10

OUTPUT POWER (mW)

603020

f = 6kHz

70

1

THD+N (%)

0.1

0.01

0.001

f = 6kHz

f = 1kHz

f = 100Hz

0 200

OUTPUT POWER (mW)

12040 80

160

TOTAL HARMONIC DISTORTION + NOISE

vs. OUTPUT POWER (HEADPHONE MODE)

100

V

= 3V

HPVDD

= 32Ω

R

MAX9791 toc23

80

L

10

1

THD+N (%)

0.1

f = 100Hz

0.01

0.001
05040 70

10

f = 1kHz

OUTPUT POWER (mW)

MAX9791 toc24A

f = 6kHz

603020

1

THD+N (%)

0.1

f = 100Hz

0.01

0.001
0 50 250

f = 1kHz

100

150

OUTPUT POWER (mW)

OUTPUT POWER vs. LOAD RESISTANCE

(HEADPHONE MODE)

250

200

150

100

OUTPUT POWER (mW)

50

0

1 100

LOAD RESISTANCE (Ω)

f = 1kHz

THD+N = 10%

10

f = 6kHz

200

MAX9791 toc25

THD+N = 1%

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

10 ______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-

erwise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, measurement BW

= 20kHz AES17, T

A

= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,

HP_EN = 1.)

HEADPHONE

OUTPUT POWER vs. LOAD RESISTANCE

90

80

70

60

50

40

30

OUTPUT POWER (mW)

20

10

0

10 1000

250

200

150

100

50

HEADPHONE OUTPUT POWER (mW)

0

3.0 5.55.04.0 4.5

(HEADPHONE MODE)

V

HPVDD

f = 1kHz

THD+N = 10%

100

LOAD RESISTANCE (Ω)

HEADPHONE OUTPUT POWER

vs. HPVDD VOLTAGE

THD+N = 1%
f = 1kHz

Ω

RL = 32

3.5
V

(V)

HPVDD

RIGHT AND LEFT

0

FS = 707mV
VIN = -60dBFS

-20

R

-40

-60

-80

-100

OUTPUT FREQUENCY SPECTRUM (dB)

-120

-140
020

POWER DISSIPATION vs. OUTPUT POWER

= 3V

THD+N = 1%

400

350

MAX9791 toc26

300

250

200

150

100

50

POWER DISSIPATION PER CHANNEL (mW)

0

0 20025 75 125 175

vs. FREQUENCY (HEADPHONE MODE)

0

-10

-20

MAX9791 toc29

-30

-40

-50

-60

PSRR (dB)

-70

RL = 16

Ω

-80

-90

-100

-110

-120

0.01 100

OUTPUT FREQUENCY SPECTRUM

(HEADPHONE MODE)

RMS

Ω

= 32

L

51015

FREQUENCY (kHz)

(HEADPHONE MODE)

RL = 16Ω

RL = 32Ω

50 100 150

PER CHANNEL OUTPUT POWER (mW)

POWER-SUPPLY REJECTION RATIO

V

= 200mV

RIPPLE

RL = 32Ω

P-P

RIGHT

LEFT

0.1 1 10
FREQUENCY (kHz)

MAX9791 toc32

POWER DISSIPATION vs. OUTPUT POWER

(HEADPHONE MODE)

300

V

= 3V

HPVDD

250

MAX9791 toc27

200

150

100

50

POWER DISSIPATION PER CHANNEL (mW)

0

20

0 1008040 60

PER CHANNEL OUTPUT POWER (mW)

RL = 16

Ω

RL = 32

Ω

CROSSTALK vs. FREQUENCY

(HEADPHONE MODE)

-20

RIGHT TO LEFT

-30

MAX9791 toc30

COM AND SENSE
DISABLED

-40

-50

-60

RIGHT TO LEFT

-70

CROSSTALK (dB)

COM AND SENSE

-80

-90

-100

0.01 100

STARTUP WAVEFORM

200μs/div

RIGHT TO LEFT
COM AND SENSE
DISABLED

0.1 1 10
FREQUENCY (kHz)

MAX9791 toc33

RL = 32
FS = 300mV
VIN = -20dBFS

LEFT TO RIGHT
COM AND SENSE

HP_EN
2V/div

HP_
500mV/div

MAX9791 toc28

Ω

RMS

MAX9791 toc31

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

______________________________________________________________________________________

11

HEADPHONE

Typical Operating Characteristics (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-

erwise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, measurement BW

= 20kHz AES17, T

A

= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,

HP_EN = 1.)

SHUTDOWN WAVEFORM

200μs/div

MAX9791 toc34

HP_EN
2V/div

HP_
500mV/div

-10

-30

-50

-70

AMPLITUDE (dBV)

-90

-110

-130

HEADPHONE RF IMMUNITY

vs. FREQUENCY

RL = 32Ω

MAX9791 toc35

LEFT

RIGHT

500 15001000 2000 2500 3000

FREQUENCY (MHz)

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

12 ______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-

erwise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, measurement BW

= 20kHz AES17, T

A

= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,

HP_EN = 1.)

LINE OUT

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
0 3.02.50.5

V

HPVDD

= 3V

R

L

= 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 = 707mV

RMS

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
R

L

= 10kΩ

FS = 300mV

RMS

VIN = -60dBFS

TOTAL HARMONIC DISTORTION + NOISE

vs. FREQUENCY (HEADPHONE MODE)

0

-10

-20

-30

-40

-50

-60

THD+N (dBFS)

-70

-80

-90

-100

-110

0.01 100

RL = 10kΩ

= -3dBFS

V

IN

FS = 707mV

0.1 1 10
FREQUENCY (kHz)

RMS

FS = 1V

RMS

MAX9791 toc36

TOTAL HARMONIC DISTORTION + NOISE

vs. FREQUENCY (HEADPHONE MODE)

0

V

= 3V

HPVDD

-10

= 10kΩ

R

L

-20

= -3dBFS

V

IN

-30

-40

-50

-60

THD+N (dBFS)

-100

-110

FS = 707mV

-70

-80

-90

0.01 100

0.1 1 10
FREQUENCY (kHz)

RMS

FS = 1V

MAX9791 toc37

RMS

TOTAL HARMONIC DISTORTION + NOISE

vs. OUTPUT POWER (HEADPHONE MODE)

100

10

1

0.1

THD+N (%)

0.01

0.001

0.0001

Ω

RL = 10k

f = 6kHz

f = 1kHz

1.0 2.0 3.0

0 4.00.5 1.5 2.5 3.5

OUTPUT POWER (mW)

f = 100Hz

MAX9791 toc38

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

______________________________________________________________________________________

13

Typical Operating Characteristics (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-

erwise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, measurement BW

= 20kHz AES17, T

A

= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,

HP_EN = 1.)

GENERAL

SUPPLY CURRENT (mA)

SUPPLY CURRENT vs. SUPPLY VOLTAGE

20

LDO_EN = 1

15

10

SPKR_EN = 0
HP_EN = 1

5

0

SPKR_EN = 1
HP_EN = 0

-5

4.50 5.505.25

4.75 5.00
SUPPLY VOLTAGE (V)

SPKR_EN = 0
HP_EN = 0

SPKR_EN = 1
HP_EN = 1

MAX9791 toc42

SHUTDOWN CURRENT vs. SUPPLY VOLTAGE

0.20

SPKR_EN = 1
HP_EN = 0
LDO_EN = 0

0.16

0.12

0.08

SHUTDOWN CURRENT (μA)

0.04

0

4.50 5.505.25

4.75 5.00
SUPPLY VOLTAGE (V)

MAX9791 toc43

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

14 ______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-

erwise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, measurement BW

= 20kHz AES17, T

A

= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,

HP_EN = 1.)

LDO

2.0

1.5

1.0

0.5

0

-0.5

-1.0

LDO OUTPUT ACCURACY (%)

-1.5

-2.0
0 15025 10050

LDO OUTPUT ACCURACY

vs. LOAD CURRENT

LOAD CURRENT (mA)

12575

0.10

0.09

MAX9791 toc44

0.08

0.07

0.06

0.05

0.04

0.03

LDO OUTPUT ACCURACY (%)

0.02

0.01

0

LDO OUTPUT ACCURACY

vs. AMPLIFIER OUTPUT POWER

0 15001200600 900

300

AMPLIFIER OUTPUT POWER (mW)

LDO OUTPUT ACCURACY

vs. TEMPERATURE

1.0

MAX9791 toc45

0.5

0

-0.5

LDO OUTPUT ACCURACY (%)

-1.0

-40 85

LDO_OUT = 3.3V

LDO_OUT = 4.75V

TEMPERATURE (°C)

MAX9791 toc46

603510-15

LDO DROPOUT VOLTAGE vs. LOAD

300

LDO_OUT = 4.75V

250

200

150

100

LDO DROPOUT VOLTAGE (mV)

50

0

0 100 15050 200 250 300

I

(mA)

LOAD

MAX9791 toc47

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY LDO

40

V

= 200mV

RIPPLE

I

LOAD

20

0

-20

PSRR (dB)

-40

-60

-80

-100

0.01 100

P-P

= 10mA

LDO_OUT = 4.74V

FREQUENCY (kHz)

LDO_OUT = 3.3V

200

175

MAX9791 toc48

150

125

100

LDO OUTPUT NOISE (μV)

75

50

1010.1

0.01 100
FREQUENCY (kHz)

C
I

LOAD

LOAD

= 2 x 1μF

= 120mA

1010.1

MAX9791 toc49

LDO OUTPUT NOISE

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

______________________________________________________________________________________

15

Typical Operating Characteristics (continued)

(V

AVDD

= V

PVDD

= V

HPVDD

= 5V, V

GND

= V

PGND

= V

CPGND

= 0, I

LDO_OUT

= 0, C

LDO

= 2 x 1µF, C1 = C2 = 1µF. RL= ∞, unless oth-

erwise specified. R

IN1

= 20kΩ (A

VSPKR

= 12dB), R

IN2

= 40.2kΩ (A

VHP

= 0dB), C

IN1

= 470nF, C

IN2

= C

COM

= 1µF, measurement BW

= 20kHz AES17, T

A

= +25°C, unless otherwise noted. Speaker mode: SPKR_EN = 0, HP_EN = 0. Headphone mode: SPKR_EN = 1,

HP_EN = 1.)

LDO

200μs/div

SHUTDOWN RESPONSE

LDO_EN
2V/div

MAX9791 toc52

V

LDO_EN

2V/div

100ms/div

LOAD-TRANSIENT RESPONSE

I

LDO_OUT

50mV/div

MAX9791 toc51

AC-COUPLED
V

LDO_OUT

10mV/div

1.00ms/div

LINE-TRANSIENT RESPONSE

CH1 LOW

4.560V

CH1 HIGH

5.500V

CH2 HIGH

1.000mV

CH2 LOW

800.0μV

MAX9791 toc50

CROSSTALK vs. FREQUENCY

0

BOTH SPEAKERS WITH SIGNAL

-10
P

-20
R

-30

I

-40

-50

-60

-70

-80

CROSSTALK (dB)

-90

-100

-110

-120

-130

0.01 100

SPEAKER TO LDO

= 1.2W

SPKR

= 8W

LSPKR

= 10mA

LDO

RIGHT CHANNEL TO LDO

MAX9791 toc53

LEFT CHANNEL TO LDO

1010.1

FREQUENCY (kHz)

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

16 ______________________________________________________________________________________

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 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 H ead p hone Am p l i fi er N eg ati ve P ow er S up p l y. C onnect a 1µF cap aci tor b etw een C P V S S and P G N D .

13 C1N C har g e- P um p Fl yi ng C ap aci tor N eg ati ve Ter m i nal . C onnect a 1µF cap aci tor b etw een C 1P and C 1N .

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 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

______________________________________________________________________________________ 17

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 head­phone amplifier, and a 120mA LDO linear regulator in a
single device.

The MAX9791/MAX9792 feature wake-on-beep detec­tion, comprehensive click-and-pop suppression, low­power shutdown mode, and excellent RF immunity.
These devices incorporate an integrated LDO that
serves as a clean power supply for CODEC or other cir­cuits. 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 mod­ulation and active emission limiting circuitry that offers
significant improvements to switch-mode amplifier tech­nology. These devices offer Class AB performance with
Class D efficiency in a minimal board-space solution.

The headphone amplifiers use Maxim’s patented
DirectDrive architecture to eliminate the bulky output
DC-blocking capacitors required by traditional head­phone amplifiers. A charge pump inverts the positive
supply (HPVDD) to create a negative supply (CPVSS).
The headphone amplifiers operate from these bipolar
supplies with their outputs biased about GND. The ben­efit of the GND bias is that the amplifier outputs no
longer have a DC component (typically V

DD

/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

18 ______________________________________________________________________________________

conserve board space and system cost, as well as
improve low-frequency response and distortion.

The MAX9791/MAX9792 amplifiers feature an under­voltage lockout that prevents operation from an insuffi­cient power supply and click-and-pop suppression that
eliminates audible transients on startup and shutdown.
The amplifiers include thermal overload and short-cir­cuit 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 tran­sistors. 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.

Figure 1. MAX9791 Efficiency vs. Class AB Efficiency

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.

WINDOWS PREMIUM

DEVICE TYPE REQUIREMENT

Analog Line-Out Jack
(R

= 10kΩ, FS =

L

0.707V

Analog Headphone-Out
Jack (R

0.300V

)

RMS

= 32Ω, FS =

L

)

RMS

THD+N ≤ -65dB FS [100Hz, 20kHz] 87dBFS [100Hz, 20kHz]

Dynamic range with signal
present

Line output crosstalk ≤ -50dB [20Hz, 15kHz] 64dB [20Hz, 15kHz]

THD+N ≤ -45dB FS [100Hz, 20kHz] 82dBFS [100Hz, 20kHz]

Dynamic range with signal
present

Headphone output
crosstalk

MOBILE VISTA

SPECIFICATIONS

≤ -80dBV, A-weighted [20Hz,
20kHz]

≤ -60dBV, A-weighted [20Hz,
20kHz]

≤ -50dB [20Hz, 15kHz] 64dB [20Hz, 15kHz]

MAX9791/MAX9792

TYPICAL PERFORMANCE

-98.9dB A-weighted [20Hz, 20kHz]

-91.5dB A-weighted [20Hz, 20kHz]

EFFICIENCY vs. IDEAL

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

CLASS AB EFFICIENCY

MAX9791

IDEAL CLASS AB

0 0.500.25 0.75 1.00 1.25 1.50

OUTPUT POWER (W)

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

______________________________________________________________________________________ 19

In addition to active emission limiting, the MAX9791/
MAX9792 feature patented spread-spectrum modulation
that flattens 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 frequency 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 con­tinue 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 sup­ply). Large coupling capacitors are needed to block
this DC bias from the headphone. Without these capac­itors, a significant amount of DC current flows to the
headphone, resulting in unnecessary power dissipation
and possible damage to both headphone and head­phone amplifier.

Maxim’s patented 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 inter­fere with audio signals. The switch drivers feature a
controlled switching speed that minimizes noise gener­ated 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.

Figure 2. EMI with 30cm of Speaker Cable

Figure 3. Traditional Amplifier Output vs. MAX9791/MAX9792
DirectDrive Output

40

35

30

25

20

AMPLITUDE (dBμV/m)

15

10

5

30 1000

CLASS D EMI PLOT

100

FREQUENCY (MHz)

V

DD

V

OUT

CONVENTIONAL AMPLIFIER BIASING SCHEME

V

OUT

DirectDrive AMPLIFIER BIASING SCHEME

VDD/2

GND

+V

GND

-V

DD

DD

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

20 ______________________________________________________________________________________

Common-Mode Sense

Windows Vista-compliant platforms are restricted to only
115mΩ of ground return impedance. If the headphone
jack ground is connected close to the audio device
ground using a solid ground plane, the return path resis­tance 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 rejec­tion, use the same value resistors for R

IN2

and R

COM

.

To improve AC CMRR, add a capacitor equal to C

IN2

between GND and R

COM

.

Configuring SENSE and COM in this way improves sys­tem 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,
R

S

. 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–90mΩ alone.

The MAX9791/MAX9792 COM and SENSE inputs
reduce crosstalk performance by eliminating effects of

28.5mΩ of 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.

Figure 4. Connecting COM for Ground Sense

Figure 5. Crosstalk vs. Ground Resistance

R

FHP

vs. GROUND RESISTANCE (RG)

C

IN2

C

COM

C

IN2

HP_INL

R

IN2

R

COM

R

COM

HP_INR

R

IN2

FHP

R

FHP

HPL

HPR

SENSE

-40
RS = 5Ω

= 32Ω

R

-45

L

-50

-55

-60

-65

CROSSTALK (dB)

-70

-75

-80

0 0.0500.025 0.075 0.100 0.125 0.150

CROSSTALK

RG (Ω)

Crosstalk in dB

20 log

=

⎛
⎜

RR

⎝

⎞

R

G

⎟

+

⎠

LS

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

______________________________________________________________________________________ 21

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 consecu­tive 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 pro­files 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 0.1µA 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.

Figure 6. MAX9791/MAX9792 COM and SENSE Inputs Reduce
Crosstalk

Figure 7. Qualified BEEP Signal Timing

CROSSTALK vs. FREQUENCY

(HEADPHONE MODE)

-20
RIGHT TO LEFT

COM AND SENSE

-30
DISABLED

-40

-50

-60

-70

CROSSTALK (dB)

-80

-90

-100

0.01 100

LEFT TO RIGHT
COM AND SENSE
DISABLED

RIGHT TO LEFT
COM AND SENSE

FREQUENCY (kHz)

RL = 32Ω
FS = 300mV
V

= -20dBFS

OUT

LEFT TO RIGHT
COM AND SENSE

1010.1

RMS

16ms

BEEP

SPKR AND HP
AMPS ENABLE

1

2

3

4

240ms

400μs

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

22 ______________________________________________________________________________________

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 RINx CINtime constant is
eliminated.

Speaker Amplifier

The MAX9791/MAX9792 speaker amplifiers feature
Maxim’s comprehensive, industry leading click-and­pop 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, typi­cally VDD/2. During shutdown, the capacitor is dis­charged 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 peak­to-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 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, and more efficient solution.

Because the frequency of the MAX9791/MAX9792 out­put 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 8Ω speakers exhibit
series inductances in the 20µH to 100µH range.

Figure 8. Enabling Either the Speaker or Headphone Amplifier
with a Single Control Pin

Figure 9. Setting Speaker Amplifier Gain

MAX9791

R

20kΩ

FB

MONO

CLASS D

AMPLIFIER

OUT_+

OUT_-

SINGLE

CONTROL

SPKR_EN

HP_EN

MAX9791A/B

MAX9792A

C

IN1

R

IN1

SPKR_IN_

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

______________________________________________________________________________________ 23

Setting Speaker Amplifier Gain

External input resistors in conjunction with the internal
feedback resistors (R

FSPKR

) set the speaker amplifier
gain of the MAX9791/MAX9792. Set gain by using
resistor R

IN1

as follows (Figure 9):

where A

VSPKR

is the desired voltage gain. An R

IN1

of

20kΩ yields 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 sup­pression. Use a ferrite bead with low DC resistance,
high frequency (> 1.2MHz) impedance of 100Ω to
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 worst­case 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 head­room of CPVSS. In typical stereo audio applications, the
left and right signals have differences in both magni­tude 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 (R

FHP

) set the headphone amplifier
gain of the MAX9791/MAX9792. Set gain by using
resistor R

IN2

(Figure 4) as follows:

where A

VHP

is the desired voltage gain. An R

IN2

of

40.2kΩ yields a gain of 1V/V, or 0dB.

Power Supplies

The MAX9791/MAX9792 speaker amplifiers are pow­ered from PVDD with a range from 4.5V 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 ampli­fiers. The charge pump inverts the voltage at HPVDD,
and the resulting voltage appears at CPVSS. AVDD
powers the remainder of the device.

Figure 10. Optional Ferrite Bead Filter

Figure 11. Output Power vs. Supply Voltage with Inputs In/Out
of Phase; 32W Load Conditions and 3.5dB Gain

A

VSPKR

⎛

⎞

Ω

k

20

=

-4

⎜

R

⎝

IN

1

VV

⎟
⎠

/

A

=

VHP

⎛

40 2

-

⎜
⎝

./Ω

R

IN

⎞

k

VV

⎟
⎠

2

MAX9791A/B

MAX9792A

*L1 = L2 = WÜRTH 742792040

TOTAL HARMONIC DISTORTION + NOISE

vs. OUTPUT POWER (HEADPHONE MODE)

100

RL = 32Ω

10

1

THD+N (%)

0.1

0.01

0.001

IN PHASE

0 250

L1*

L2*

330pF 330pF

OUT OF PHASE

20015010050

OUTPUT POWER (mW)

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

24 ______________________________________________________________________________________

Component Selection

Speaker Amplifier Power-Supply Input (PVDD)

PVDD powers the speaker amplifiers. PVDD ranges
from 4.5V to 5.5V. 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 head­phone 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 4.5V to 5.5V.
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 (C

IN_

), in conjunction with the

amplifier input resistance (R

IN_

), 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 impedance, the -3dB point of the highpass filter
is given by:

R

IN_

is the amplifier’s external input resistance value.

Choose C

IN_

such that f

-3dB

is well below the lowest fre-

quency of interest. Setting f

-3dB

too high affects the ampli­fier’s low frequency response. Use capacitors with
adequately low-voltage coefficient dielectrics (see Figure

12). Capacitors with higher voltage coefficients, such as
ceramics, result in increased distortion at low frequencies.

Charge-Pump Capacitor Selection

Use capacitors with an ESR less than 100mΩ for opti­mum performance. Low ESR ceramic capacitors mini­mize 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.

Figure 12. Input Coupling Capacitor-Induced THD+N vs.
Frequency

Figure 13. Speaker RF Immunity

INPUT COUPLING CAPACITOR-INDUCED THD+N

vs. FREQUENCY (HEADPHONE MODE)

-50

0603 10V X7R 10% 1μF

-60

-70

-80

THD+N (dBFS)

-90

0402 6.3V X5R 10% 1μF

-100
10 1000

FREQUENCY (kHz)

V

- -3dBFS

OUT

FS = 1V

RMS

RL =32Ω

0603 10V X5R 10% 1μF

0805 50V X7R 10% 1μF

100

SPEAKER RF IMMUNITY

vs. FREQUENCY

0

-10

-20

-30

-40

-50

-60

-70

-80

AMPLITUDE (dBV)

-90

-100

-110

-120

-130
0 3000

RIGHT

LEFT

2500200015001000500

FREQUENCY (MHz)

f

dB

-3

RC

2=π

IN IN

1

__

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

______________________________________________________________________________________ 25

Output Capacitor (C2)

Connect a 1µF capacitor between CPVSS and PGND.

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 per­formance, 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 charge­pump 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 imped­ance decreases, the current drawn from the device out­puts 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 4Ω load through a 100mΩ trace, 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 dissi­pation 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

26 ______________________________________________________________________________________

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

MAX9791A
MAX9791B

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

Pin Configurations

TOP VIEW

SPKR_EN

SPKR_IN

HP_EN

22

PGND

23

24

OUT+

25

OUT-

26

PVDD

27

28

*EP = EXPOSED PAD

PGND

OUT-

BEEP

2021 19 17 16 15

MAX9792A

+

12

3

GND

HP_INR

PVDD

OUT+

18

*EP

4567

GND

COM

HP_INL

HPVDD

C1P

AVDD

LDO_OUT

14

CPGND

C1N

13

12

CPVSS

SENSE

11

10

HPL

HPR

9

8

LDO_EN

TQFN

(4mm x 4mm x 0.75mm)

SPEAKER SUPPLY

4.5V TO 5.5V

HEADPHONE SUPPLY

2.7V TO 5.5V

SPKR_IN

MAX9792A

HP_INR

HP_INL

4.5V TO 5.5V

SPKR_EN
HP_EN

LDO_EN
BEEP

LDO

CLASS D

AMP

4.75V

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

______________________________________________________________________________________ 27

MAX9791A/MAX9791B Block Diagram

C

IN3

R

IN3

C

RIN1

IN1

CIN1

RIN1

C

IN3

R

IN3

C

IN2

R

IN2

C

IN2

R

IN2

4.5V TO 5.5V

μC BEEP INPUT

C

COM

4.5V TO 5.5V

1.0μF1.0μF

TO CODEC

1.0μF

NOTE: LOGIC PINS CONFIGURED FOR:
LDO_EN = 1, LDO ENABLED
SPKR_EN = 0, SPEAKER AMPLIFIERS ENABLED
HP_EN = 1, HEADPHONE AMPLIFIER ENABLED

0.1μF

1.0μF

R

COM

SPKR_INL

SPKR_INR

HP_INL

HP_INR

LDO_EN

HP_EN 22

BEEP 21

SPKR_EN

COM

AVDD

LDO_OUT

4.5V TO 5.5V

0.1μF

PVDD

17, 26

MAX9791A

40.2kΩ

MAX9791B

40.2kΩ

TO HPVDD

TO CPVSS

TO HPVDD

40.2kΩ

CHARGE

PUMP

12
CPVSS

C2

1.0μF

19 OUTL+

OUTL-

18

OUTR+

24

25

OUTR-

10

HPL

HPR

9

SENSE

11

HPVDD

16

C1P

15

CPGND

14

C1N

13

2.7V TO 5.5V

C1

1.0μF

C3
10μF

20kΩ

1

STEREO

CLASS D

28

20kΩ

3

2

8

CONTROL

27

4

7

LDO BLOCK

6

5

AMPLIFIER

20, 23

PGNDGND

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker
Amplifiers with DirectDrive Headphone Amplifiers

28 ______________________________________________________________________________________

MAX9792A Block Diagram

4.5V TO 5.5V

0.1μF

PVDD

17, 26

MAX9792A

C

IN3

R

IN3

C

RIN1

IN1

C

IN2

R

IN2

SPKR_IN

HP_INL

28

3

C

IN2

R

IN2

4.5V TO 5.5V

μC BEEP INPUT

C

COM

4.5V TO 5.5V

1.0μF1.0μF

TO CODEC

1.0μF

NOTE: LOGIC PINS CONFIGURED FOR:
LDO_EN = 1, LDO ENABLED
SPKR_EN = 0, SPEAKER AMPLIFIER ENABLED
HP_EN = 1, HEADPHONE AMPLIFIER ENABLED

0.1μF

1.0μF

R

COM

HP_INR

LDO_EN

HP_EN 22

BEEP 21

SPKR_EN

COM

AVDD

LDO_OUT

2

8

27

4

7

6

20kΩ

CONTROL

LDO BLOCK

1, 5

MONO

CLASS D

AMPLIFIER

40.2kΩ

20, 23

PGNDGND

MAX9792B

40.2kΩ

TO HPVDD

TO CPVSS

TO HPVDD

40.2kΩ

CHARGE

PUMP

12

CPVSS

C2

1.0μF

19, 24 OUT+

OUT-

18, 25

10

HPL

HPR

9

SENSE

11

HPVDD

16

C1P

15

CPGND

14

C1N

13

2.7V TO 5.5V

C1

1.0μF

C3
10μF

MAX9791/MAX9792

Windows Vista-Compliant Class D Speaker

Amplifiers with DirectDrive Headphone Amplifiers

______________________________________________________________________________________ 29

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

28 TQFN-EP T2844-1

21-0139

Package Information

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

24L QFN THIN.EPS

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.

30

____________________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.

Package Information (continued)

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.