MAXIM MAX9712 User Manual

General Description

The MAX9712 mono class D audio power amplifier pro­vides class AB amplifier performance with class D effi­ciency, conserving board space, and extending battery
life. Using a class D architecture, the MAX9712 delivers
up to 500mW into an 8Ω load while offering efficiencies
above 85%. A low EMI modulation scheme renders the
traditional class D output filter unnecessary.

The MAX9712 offers two modulation schemes: a fixed­frequency (FFM) mode, and a spread-spectrum (SSM)
mode that reduces EMI-radiated emissions due to the
modulation frequency. Furthermore, the MAX9712 oscil­lator can be synchronized to an external clock through
the SYNC input, allowing the switching frequency to be
user defined. The SYNC input also allows multiple
MAX9712s to be cascaded and frequency locked, mini­mizing interference due to clock intermodulation. The
device utilizes a fully differential architecture, a full­bridged output, and comprehensive click-and-pop sup­pression. The gain is internally set to +4V/V, further
reducing external component count.

The MAX9712 features high 72dB PSRR, a low 0.01%
THD+N, and SNR in excess of 90dB. Short-circuit and
thermal-overload protection prevent the device from
damage during a fault condition. The MAX9712 is avail­able in 10-pin TDFN (3mm ✕3mm ✕0.8mm), 10-pin
µMAX, and 12-bump UCSP™ (1.5mm ✕2mm ✕ 0.6mm)
packages. The MAX9712 is specified over the extended

-40°C to +85°C temperature range.

Applications

Features

♦ Filterless Amplifier Passes FCC Radiated

Emissions Standards with 100mm of Cable

♦ Unique Spread-Spectrum Mode Offers 5dB

Emissions Improvement Over Conventional
Methods

♦ Optional External SYNC Input
♦ Simple Master-Slave Setup for Stereo Operation
♦ 85% Efficiency
♦ Up to 500mW into 8Ω
♦ Low 0.01% THD+N
♦ High PSRR (72dB at 217Hz)
♦ Integrated Click-and-Pop Suppression
♦ Low Quiescent Current (4mA)
♦ Low-Power Shutdown Mode (0.1µA)
♦ Short-Circuit and Thermal-Overload Protection
♦ Available in Thermally Efficient, Space-Saving

Packages

10-Pin TDFN (3mm

✕

3mm ✕ 0.8mm)

10-Pin µMAX

12-Bump UCSP (1.5mm ✕2mm ✕0.6mm)

MAX9712

500mW, Low EMI, Filterless,

Class D Audio Amplifier

________________________________________________________________ Maxim Integrated Products 1

1

2

3

4

5

10

9

8

7

6

PV

DD

OUT-

OUT+

PGNDGND

IN-

IN+

V

DD

MAX9712

TDFN/μMAX

TOP VIEW

SYNCSHDN

Pin Configurations

Ordering Information

MAX9712

DIFFERENTIAL

AUDIO INPUT

SYNC

INPUT

V

DD

OSCILLATOR

MODULATOR

AND H-BRIDGE

Simplified Block Diagram

19-2917; Rev 1; 1/04

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Cellular Phones
PDAs

MP3 Players
Portable Audio

PART

PIN/BUMP­PACKAGE

TOP

MARK

MAX9712ETB

10 TDFN AAI

MAX9712EUB

10 µMAX —

MAX9712EBC-T

ABN

Pin Configurations continued at end of data sheet.

UCSP is a trademark of Maxim Integrated Products, Inc.

TEMP RANGE

-40°C to +85°C

-40°C to +85°C

-40°C to +85°C 12 UCSP-12

500mW, Low EMI, Filterless,
Class D Audio Amplifier

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VDD= PVDD= SHDN = 3.3V, GND = PGND = 0V, SYNC = GND (FFM), RL= 8Ω, RLconnected between OUT+ and OUT-, TA=

T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.) (Notes 1, 2)

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.

VDDto GND..............................................................................6V

PV

DD

to PGND .........................................................................6V

GND to PGND .......................................................-0.3V to +0.3V

All Other Pins to GND.................................-0.3V to (V

DD

+ 0.3V)

Continuous Current Into/Out of PV

DD

/PGND/OUT_........±600mA

Continuous Input Current (all other pins)..........................±20mA

Duration of OUT_ Short Circuit to GND or PV

DD

........Continuous

Duration of Short Circuit Between OUT+ and OUT- ..Continuous

Continuous Power Dissipation (T

A

= +70°C)

10-Pin TDFN (derate 24.4mW/°C above +70°C) .....1951.2mW

10-Pin µMAX (derate 5.6mW/

o

C above +70°C).........444.4mW

12-Bump UCSP (derate 6.1mW/°C above +70°C)........484mW

Junction Temperature......................................................+150°C

Operating Temperature Range ...........................-40°C to +85°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

Bump Temperature (soldering)

Reflow ..........................................................................+235°C

MAX9712

PARAMETER

CONDITIONS

UNITS

GENERAL

Supply Voltage Range V

DD

Inferred from PSRR test 2.5 5.5 V

Quiescent Current I

DD

4 5.2 mA

Shutdown Current I

SHDN

0.1 5 µA

Turn-On Time t

ON

30 ms

Input Resistance R

IN

TA = +25°C 14 20 kΩ

Input Bias Voltage V

BIAS

Either input

V

Voltage Gain A

V

3.8 4 4.2 V/V

±40

TA = +25°C

M AX 9712E BC

±65
±65

Output Offset Voltage V

OS

T

MIN

≤ TA ≤

T

MAX M AX 9712E BC ±95

mV

Common-Mode Rejection Ratio CMRR fIN = 1kHz, input referred 72 dB

VDD = 2.5V to 5.5V 50 70

f

RIPPLE

= 217Hz 72

Power-Supply Rejection Ratio
(Note 3)

PSRR

200mV

P-P

ripple

f

RIPPLE

= 20kHz 55

dB

RL = 8Ω

Output Power P

OUT

THD+N = 1%

R

L

= 6Ω

mW

RL = 8Ω,
P

OUT

= 125mW

Total Harmonic Distortion Plus
Noise

fIN = 1kHz, either
FFM or SSM

R

L

= 6Ω,

P

OUT

= 125mW

%

SYMBOL

MIN TYP MAX

0.73 0.83 0.93

M AX 9712E U B/M AX 9712E TB ±11

±15

450
250

0.01

0.01

THD+N

M AX 9712E U B/M AX 9712E TB

RL = 16Ω, VDD = 5V 700

MAX9712

500mW, Low EMI, Filterless,

Class D Audio Amplifier

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VDD= PVDD= SHDN = 3.3V, GND = PGND = 0V, SYNC = GND (FFM), RL= 8Ω, RLconnected between OUT+ and OUT-, TA=
T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.) (Notes 1, 2)

Note 1: All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design.
Note 2: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For R

L

= 6Ω, L = 47µH.

For R

L

= 8Ω, L = 68µH. For RL= 16Ω, L = 136µH.

Note 3: PSRR is specified with the amplifier inputs connected to GND through C

IN

.

PARAMETER

CONDITIONS

UNITS

FFM 88

BW = 22Hz
to 22kHz

SSM 86
FFM 91

Signal-to-Noise Ratio SNR V

OUT

= 1.8V

RMS

SSM 89

dB

SYNC = GND 980
SYNC = float

Oscillator Frequency f

OSC

SYNC = VDD (SSM mode)

kHz

SYNC Frequency Lock Range 800

kHz

Efficiency η P

OUT

= 300mW, fIN = 1kHz 85 %

DIGITAL INPUTS (SHDN, SYNC)

V

IH

2

Input Thresholds

V

IL

0.8

V

SHDN Input Leakage Current ±1µA
SYNC Input Current ±5µA

Typical Operating Characteristics

(VDD= 3.3V, V

SYNC

= GND, TA= +25°C, unless otherwise noted.)

0.001
10 100k10k100 1k

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY

1

0.1

0.01

MAX9712 TOC01

FREQUENCY (Hz)

THD+N (%)

VDD = +5V
R

L

= 8Ω

P

OUT

= 300mW

P

OUT

= 125mW

0.001
10 100k10k100 1k

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY

1

0.1

0.01

MAX9712 TOC02

FREQUENCY (Hz)

THD+N (%)

VDD = +3.3V
R

L

= 8Ω

P

OUT

= 300mW

P

OUT

= 125mW

0.001
10 100k10k100 1k

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY

1

0.1

0.01

MAX9712 TOC03

FREQUENCY (Hz)

THD+N (%)

VDD = +3.3V
R

L

= 8Ω

P

OUT

= 125mW

SSM MODE

FFM MODE

SYMBOL

A-weighted

MIN TYP MAX

1100 1220

1280 1450 1620

1220
±120

2000

MAX9712

500mW, Low EMI, Filterless,
Class D Audio Amplifier

4 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VDD= 3.3V, V

SYNC

= GND, TA= +25°C, unless otherwise noted.)

100

00.1 0.2 0.3 0.4 0.5

10

1

0.1

0.01

0.001

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER

MAX9712 TOC04

OUTPUT POWER (W)

THD+N (%)

VDD = 3.3V
R

L

= 8Ω

f = 10kHz

f = 1kHz

f = 100Hz

100

0 0.2 0.4 0.6 0.8 1.0

10

1

0.1

0.01

0.001

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER

MAX9712 TOC05

OUTPUT POWER (W)

THD+N (%)

VDD = 5V
R

L

= 16Ω

f = 10kHz

f = 1kHz

f = 100Hz

100

0 0.1 0.2 0.3 0.4

10

1

0.1

0.01

0.001

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER

MAX9712 TOC06

OUTPUT POWER (W)

THD+N (%)

VDD = 3.3V
R

L

= 6Ω

f = 1kHz

f = 100Hz

f = 10kHz

100

0 0.1 0.2 0.3 0.4 0.5

10

1

0.1

0.01

0.001

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER

MAX9712 TOC07

OUTPUT POWER (W)

THD+N (%)

VDD = 2.5V
R

L

= 8Ω

V

CM

= 1.25V

NO INPUT CAPACITORS

DIFFERENTIAL
INPUT

SINGLE-ENDED

100

0 0.1 0.2 0.3 0.4 0.5

10

1

0.1

0.01

0.001

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER

MAX9712 TOC08

OUTPUT POWER (W)

THD+N (%)

VDD = 3.3V
R

L

= 8Ω

FFM
(SYNC FLOATING)

FFM
(SYNC = GND)

SSM
(SYNC = V

DD

)

100

00.10.2 0.3 0.4 0.5 0.6

10

1

0.1

0.01

0.001

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER

MAX9712 TOC09

OUTPUT POWER (W)

THD+N (%)

VDD = 3.3V
R

L

= 8Ω

SYNC = 3.3V

P-P

50% DUTY CYCLE
SQUARE WAVE

f

SYNC

= 1.4MHz

f

SYNC

= 2MHz

f

SYNC

= 800kHz

10

00.51.01.52.02.53.0

1

0.1

0.01

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. COMMON-MODE VOLTAGE

MAX9712 TOC10

COMMON-MODE VOLTAGE (V)

THD+N (%)

VDD = 3.3V
R

L

= 8Ω
f = 1kHz
P

OUT

= 300mW

DIFFERENTIAL INPUT

0

30
20
10

50
40

90
80
70
60

100

00.10.20.3 0.4 0.5 0.6 0.7

EFFICIENCY vs. OUTPUT POWER

MAX9712TOC11

OUTPUT POWER (W)

EFFICIENCY (%)

RL = 8Ω

VDD = 5V
f = 1kHz

RL = 16Ω

0

30
20
10

50
40

90
80
70
60

100

00.10.20.3 0.4 0.5

EFFICIENCY vs. OUTPUT POWER

MAX9712TOC12

OUTPUT POWER (W)

EFFICIENCY (%)

RL = 8Ω

RL = 6Ω

VDD = 3.3V
f = 1kHz

RL = 16Ω

MAX9712

500mW, Low EMI, Filterless,

Class D Audio Amplifier

_______________________________________________________________________________________ 5

0

30
20
10

50
40

90
80
70
60

100

2.5 3.0 3.5 4.0 4.5 5.0 5.5

EFFICIENCY vs. SUPPLY VOLTAGE

MAX9712TOC13

SUPPLY VOLTAGE (V)

EFFICIENCY (%)

RL = 8Ω

f = 1kHz

RL = 6Ω RL = 16Ω

0

30
20
10

50
40

90
80
70
60

100

800 1000 1200 1400 18001600 2000

EFFICIENCY

vs. SYNC INPUT FREQUENCY

MAX9712TOC14

SYNC FREQUENCY (kHz)

EFFICIENCY (%)

RL = 8Ω

VDD = 3.3V
f = 1kHz
P

OUT

= 300mW

0

500
400

200
100

300

700
600

900
800

1000

2.5 3.1 3.7 4.3 4.9 5.5

OUTPUT POWER

vs. SUPPLY VOLTAGE

MAX9712TOC15

SUPPLY VOLTAGE (V)

OUTPUT POWER (mW)

f = 1kHz

RL = 6Ω

RL = 8Ω

RL = 16Ω

0

300
200
100

500
400

900
800
700
600

1000

01020 4030 80706050 10090

OUTPUT POWER

vs. LOAD RESISTANCE

MAX9712TOC16

LOAD RESISTANCE (Ω)

OUTPUT POWER (mW)

VDD = 5V

VDD = 3.3V

f = 1kHz
THD+N = 1%

0

-100
10 100 1k 10k 100k

COMMON-MODE REJECTION RATIO

vs. FREQUENCY

-80

MAX9712TOC17

FREQUENCY (Hz)

CMRR (dB)

-60

-40

-20

-30

-50

-70

-90

-10

INPUT REFERRED
V

IN

= 200mV

P-P

0

-100
10 100 1k 10k 100k

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

-80

MAX9712TOC18

FREQUENCY (Hz)

PSRR (dB)

-60

-40

-20

-30

-50

-70

-90

-10

OUTPUT REFERRED
INPUTS AC GROUNDED
V

DD

= 3.3V

GSM POWER-SUPPLY REJECTION

MAX9712TOC19

MAX9712

OUTPUT

V

DD

100µV/div

500mV/div

2ms/div

f = 217Hz
INPUT LOW = 3V
INPUT HIGH = 3.5V

DUTY CYCLE = 88%
R

L

= 8Ω

-140

-100

-120

-60

-80

-20

-40

0

OUTPUT FREQUENCY SPECTRUM

MAX9712TOC20

FREQUENCY (Hz)

OUTPUT MAGNITUDE (dBV)

05k10k15k 20k

FFM MODE
V

OUT

= -60dBV
f = 1kHz
R

L

= 8Ω

UNWEIGHTED

Typical Operating Characteristics (continued)

(VDD= 3.3V, V

SYNC

= GND, TA= +25°C, unless otherwise noted.)

MAX9712

500mW, Low EMI, Filterless,
Class D Audio Amplifier

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VDD= 3.3V, V

SYNC

= GND, TA= +25°C, unless otherwise noted.)

-140

-100

-120

-60

-80

-20

-40

0

OUTPUT FREQUENCY SPECTRUM

MAX9712TOC22

FREQUENCY (kHz)

OUTPUT MAGNITUDE (dBV)

051015 20

SSM MODE
V

OUT

= -60dBV
f = 1kHz
R

L

= 8Ω

A-WEIGHTED

0

-100
1M 10M 100M 1G

WIDEBAND OUTPUT SPECTRUM

(FFM MODE)

-80

MAX1972 TOC23

FREQUENCY (Hz)

OUTPUT AMPLITUDE (dB)

-60

-40

-20

-30

-50

-70

-90

-10

RBW = 10kHz

0

-100
1M 10M 100M 1G

WIDEBAND OUTPUT SPECTRUM

(SSM MODE)

-80

MAX1972TOC24

FREQUENCY (Hz)

OUTPUT AMPLITUDE (dB)

-60

-40

-20

-30

-50

-70

-90

-10

RBW = 10kHz

TURN-ON/TURN-OFF RESPONSE

MAX9712TOC25

MAX9712

OUTPUT

SHDN

0V

250mV/div

3V

10ms/div

f = 1kHz
R

L

= 8Ω

3.0

3.5

4.5

4.0

5.5

5.0

6.0

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX9712TOC26

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

2.5 3.0 3.5 4.0 4.5 5.0 5.5

TA = +85°C

TA = +25°C

TA = -40°C

0

0.06

0.04

0.02

0.10

0.08

0.14

0.12

0.16

2.5 3.0 3.5 4.0 4.5 5.0 5.5

SHUTDOWN SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX9712 TOC27

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (

µ

A)

TA = +85°C

TA = -40°C

TA = +25°C

-140

-100

-120

-60

-80

-20

-40

0

OUTPUT FREQUENCY SPECTRUM

MAX9712TOC21

FREQUENCY (kHz)

OUTPUT MAGNITUDE (dBV)

051015 20

SSM MODE
V

OUT

= -60dBV
f = 1kHz
R

L

= 8Ω

UNWEIGHTED