Rainbow Electronics 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 patented, 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

Pin Configurations

Ordering Information

MAX9712

DIFFERENTIAL

AUDIO INPUT

SYNC

INPUT

V

DD

OSCILLATOR

MODULATOR

AND H-BRIDGE

Simplified Block Diagram

19-2917; Rev 0; 8/03

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

Pin Configurations continued at end of data sheet.

UCSP is a trademark of Maxim Integrated Products, Inc.

*Future product—contact factory for availability.

PART TEMP RANGE

MAX9712ETB -40°C to +85°C 10 TDFN AAI

MAX9712EUB -40°C to +85°C 10 µMAX —

MAX9712EBC-T* -40°C to +85°C 12 UCSP-12 ABN

PIN/BUMP­PACKAGE

TOP

MARK

TOP VIEW

V

1

DD

IN+

2

IN-

MAX9712

3

4

5

TDFN/µMAX

10

PV

DD

OUT-

9

OUT+

8

PGNDGND

7

SYNCSHDN

6

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

GENERAL

Supply Voltage Range V

Quiescent Current I

Shutdown Current I

Turn-On Time t

Input Resistance R

Input Bias Voltage V

Voltage Gain A

Output Offset Voltage V

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

Power-Supply Rejection Ratio
(Note 3)

Total Harmonic Distortion Plus
Noise

Signal-to-Noise Ratio SNR V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DD

DD

SHDN

ON

BIAS

OS

PSRR

OUT

THD+N

Inferred from PSRR test 2.5 5.5 V

TA = +25°C1420kΩ

IN

Either input 0.73 0.83 0.93 V

V

TA = +25°C ±11 40

T

≤ TA ≤ T

MIN

VDD = 2.5V to 5.5V 50 70

200mV

THD+N = 1%

f

= 1kHz, either

IN

FFM or SSM

OUT

ripple

P-P

= 1.8V

MAX

RMS

f

= 217Hz 72

RIPPLE

f

= 20kHz 55

RIPPLE

RL = 16Ω, VDD = 5V 700

RL = 8Ω 450Output Power P

= 6Ω 250

R

L

RL = 8Ω,
P

= 125mW

OUT

R

= 6Ω,

L

P

= 125mW

OUT

BW = 22Hz
to 22kHz

A-weighted

FFM 88

SSM 86

FFM 91

SSM 89

4 5.2 mA

0.1 5 µA

30 ms

3.8 4 4.2 V/V

±65

0.01

0.01

mV

dB

mW

%

dB

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

.

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

Oscillator Frequency f

SYNC Frequency Lock Range 800 2000 kHz

Efficiency η P

DIGITAL INPUTS (SHDN, SYNC)

Input Thresholds

SHDN Input Leakage Current ±1µA

SYNC Input Current ±5µA

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SYNC = GND 980 1100 1220

OSC

SYNC = float 1280 1450 1620

SYNC = VDD (SSM mode)

= 300mW, fIN = 1kHz 85 %

OUT

V

IH

V

IL

1220
±120

2

0.8

kHz

V

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

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 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

0 0.1 0.2 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

0 0.5 1.0 1.5 2.0 2.5 3.0

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

0 0.1 0.2 0.3 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

0 0.1 0.2 0.3 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

Typical Operating Characteristics (continued)

(VDD= 3.3V, V

SYNC

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

EFFICIENCY vs. SUPPLY VOLTAGE

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

f = 1kHz

0

2.5 3.0 3.5 4.0 4.5 5.0 5.5

RL = 8Ω

RL = 6Ω RL = 16Ω

SUPPLY VOLTAGE (V)

OUTPUT POWER

vs. LOAD RESISTANCE

1000

f = 1kHz

900

THD+N = 1%

800

700

600

500

400

OUTPUT POWER (mW)

300

200

100

0

01020 4030 80706050 10090

VDD = 5V

VDD = 3.3V

LOAD RESISTANCE (Ω)

MAX9712TOC13

MAX9712TOC16

EFFICIENCY

vs. SYNC INPUT FREQUENCY

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

800 1000 1200 1400 18001600 2000

SYNC FREQUENCY (kHz)

COMMON-MODE REJECTION RATIO

vs. FREQUENCY

0

INPUT REFERRED

-10

-20

-30

-40

-50

CMRR (dB)

-60

-70

-80

-90

-100

= 200mV

V

IN

P-P

10 100 1k 10k 100k

FREQUENCY (Hz)

VDD = 3.3V
f = 1kHz

= 300mW

P

OUT

RL = 8Ω

1000

900

MAX9712TOC14

800

700

600

500

400

OUTPUT POWER (mW)

300

200

100

-10

MAX1972TOC17

-20

-30

-40

-50

PSRR (dB)

-60

-70

-80

-90

-100

f = 1kHz

0

2.5 3.1 3.7 4.3 4.9 5.5

0

10 100 1k 10k 100k

OUTPUT POWER

vs. SUPPLY VOLTAGE

RL = 16Ω

RL = 8Ω

RL = 6Ω

SUPPLY VOLTAGE (V)

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

OUTPUT REFERRED
INPUTS AC GROUNDED

= 3.3V

V

DD

FREQUENCY (Hz)

MAX9712TOC15

MAX1972TOC18

V

MAX9712

OUTPUT

GSM POWER-SUPPLY REJECTION

DD

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

2ms/div

MAX9712TOC19

DUTY CYCLE = 88%

= 8Ω

R

L

500mV/div

100µV/div

OUTPUT FREQUENCY SPECTRUM

0

FFM MODE

= -60dBV

V

OUT

-20
f = 1kHz

= 8Ω

R

L

-40
UNWEIGHTED

-60

-80

-100

OUTPUT MAGNITUDE (dBV)

-120

-140
0 5k 10k 15k 20k

FREQUENCY (Hz)

MAX9712TOC20

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)

0 5 10 15 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 (µA)

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)

0 5 10 15 20

SSM MODE
V

OUT

= -60dBV
f = 1kHz
R

L

= 8Ω

UNWEIGHTED