MAXIM MAX9708 Technical data

General Description

The MAX9708 mono/stereo, Class D audio power amplifi­er delivers up to 2 x 21W into an 8Ω stereo mode and
1 x 42W into a 4Ω load in mono mode while offering up to
87% efficiency. The MAX9708 provides Class AB amplifi­er performance with the benefits of Class D efficiency,
eliminating the need for a bulky heatsink and conserving
power. The MAX9708 operates from a single +10V to
+18V supply, driving the load in a BTL configuration.

The MAX9708 offers two modulation schemes: a fixed­frequency modulation (FFM) mode, and a spread-spec­trum modulation (SSM) mode that reduces
EMI-radiated emissions. The MAX9708 can be synchro­nized to an external clock from 600kHz to 1.2MHz. A
synchronized output allows multiple units to be cascad­ed in the system.

Features include fully differential inputs, comprehensive
click-and-pop suppression, and four selectable-gain set­tings (22dB, 25dB, 29.5dB, and 36dB). A pin-program­mable thermal flag provides seven different thermal
warning thresholds. Short-circuit and thermal-overload
protection prevent the device from being damaged
during a fault condition.

The MAX9708 is available in 56-pin TQFN (8mm x 8mm
x 0.8mm) and 64-pin TQFP (10mm x 10mm x 1.4mm)
packages, and is specified over the extended

-40°C to +85°C temperature range.

Applications

LCD TVs PDP TVs

Automotive PC/HiFi Audio Solutions

Features

♦ 2 x 21W Output Power in Stereo Mode

(8Ω, THD = 10%)

♦ 1 x 42W Output Power in Mono Mode

(4Ω, THD = 10%)

♦ High Efficiency: Up to 87%
♦ Filterless Class D Amplifier
♦ Unique Spread-Spectrum Mode
♦ Programmable Gain (+22dB, +25dB, +29.5dB,

+36dB)

♦ High PSRR (90dB at 1kHz)
♦ Differential Inputs Suppress Common-Mode

Noise

♦ Shutdown and Mute Control
♦ Integrated Click-and-Pop Suppression
♦ Low 0.1% THD+N
♦ Current Limit and Thermal Protection
♦ Programmable Thermal Flag
♦ SYNC Input/Output
♦ Available in Thermally Efficient, Space-Saving

Packages: 56-Pin TQFN and 64-Pin TQFP

MAX9708

20W/40W, Filterless, Spread-Spectrum,

Mono/Stereo, Class D Amplifier

________________________________________________________________ Maxim Integrated Products 1

CLASS D

MODULATOR

SYNCOUT

TEMP

OUTPUT

PROTECTION

GAIN

CONTROL

FS1, FS2

MAX9708

STEREO MODE

G1, G2

2

SYNC

RIGHT

CHANNEL

LEFT

CHANNEL

MONO

2

TH0, TH1,

TH2

3

PART

TEMP RANGE

PIN-PACKAGE

PKG

CODE

MAX9708ETN+

T5688-3

MAX9708ECB*

64 TQFP-EP**

C64E-6

Simplified Block Diagram

Ordering Information

19-3678; Rev 2; 3/06

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.

+Denotes lead-free package.
*Future product—Contact factory for availability.
**EP = Exposed paddle.

Pin Configurations appear at end of data sheet.

EVALUATION KIT

AVAILABLE

CLASS D

MODULATOR

SYNCOUT

TEMP

OUTPUT

PROTECTION

GAIN

CONTROL

FS1, FS2

MAX9708

MONO MODE

G1, G2

2

SYNC

AUDIO

INPUT

V

DIGITAL

MONO

2

TH0, TH1,

TH2

3

-40°C to +85°C 56 TQFN-EP**

-40°C to +85°C

MAX9708

20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= ∞, MONO = low (stereo

mode),

SHDN = MUTE = high, G1 = low, G2 = high (AV= 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are

connected between OUT_+ and OUT_-, unless otherwise stated. T

A

= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 1)

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.

PVDD, VDDto PGND, GND .......................................-0.3 to +30V

PV

DD

to VDD..........................................................-0.3V to +0.3V

OUTR+, OUTR-, OUTL+,

OUTL- to PGND, GND...........................-0.3V to (PV

DD

+ 0.3V)

C1N to GND .............................................-0.3V to (PV

DD

+ 0.3V)

C1P to GND..............................(PV

DD

- 0.3V) to (CPVDD+ 0.3V)

CPV

DD

to GND ..........................................(PV

DD

- 0.3V) to +40V

All Other Pins to GND.............................................-0.3V to +12V

Continuous Input Current (except PV

DD

, VDD, OUTR+,

OUTR-, OUTL+, and OUTL-) ...........................................20mA

Continuous Power Dissipation (T

A

= +70°C)

56-Pin Thin QFN (derate 47.6mW/°C above +70°C) ......3.81W

64-Pin TQFP (derate 43.5mW/°C above +70°C).............3.48W

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

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

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

Thermal Resistance (θ

JC

)

56-Pin Thin QFN… .......................................................0.6°C/W

64-Pin TQFP….................................................................2°C/W

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

PARAMETER

CONDITIONS

UNITS

Supply Voltage Range V

DD

Inferred from PSRR test 10 18 V

Shutdown Current I

SHDN

SHDN = low 0.1 1 µA

Shutdown to Full Operation t

SON

ms

Mute to Full Operation t

MUTE

ms

G1 = 0, G2 = 1 50 85 125

G1 = 1, G2 = 1 40 63 90

G1 = 1, G2 = 0 25 43 60

Input Impedance R

IN

G1= 0, G2 = 0 12 21 30

kΩ

Output Pulldown Resistance SHDN = GND

kΩ

Output Offset Voltage V

OS

AC-coupled input, measured between
OUT_+ and OUT_-

mV

PVDD = 10V to 18V 68 90

f

RIPPLE

= 1kHz 90

Power-Supply Rejection Ratio PSRR

200mV

P-P

ripple

(Note 2)

f

RIPPLE

= 20kHz 50

dB

DC, input referred 50 70

Common-Mode Rejection Ratio CMRR

f = 20Hz to 20kHz, input referred 70

dB

Switch On-Resistance R

DS

One power switch 0.3

Ω

FS1 FS2

00

220

1 1 (SSM)

10

Switching Frequency f

SW

01

kHz

Oscillator Spread Bandwidth FS1 = FS2 = high (SSM) ±2 %

SYNCIN Lock Range Equal to fSW x 4

kHz

SYMBOL

MIN TYP MAX

100

100

600

200

160

250

180 200

600 1200

±30

0.75

MAX9708

20W/40W, Filterless, Spread-Spectrum,

Mono/Stereo, Class D Amplifier

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= ∞, MONO = low (stereo

mode), SHDN = MUTE = high, G1 = low, G2 = high (A

V

= 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are

connected between OUT_+ and OUT_-, unless otherwise stated. T

A

= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 1)

PARAMETER

CONDITIONS

UNITS

G1 = 0, G2 = 1

G1 = 1, G2 = 1

G1 = 1, G2 = 0

Gain A

V

G1 = 0, G2 = 0

dB

TH2 TH1 TH0

000

001

010

011

100

101

110

TEMP Flag Threshold T

FLAG

111

°C

TEMP Flag Accuracy From +80°C to +140°C ±6 °C
TEMP Flag Hysteresis 2°C

STEREO MODE (R

LOAD

= 8Ω)

MUTE = 1, R

LOAD

= ∞ 20 30

Quiescent Current

MUTE = 0 5 11

mA

Output Power P

OUT

f = 1kHz, THD = 10%, TA = +25°C,
R

LOAD

= 8Ω, PVDD = 18V

20 21 W

Total Harmonic Distortion Plus
Noise

f = 1kHz, BW = 22Hz to 22kHz,
R

LOAD

= 8Ω, P

OUT

= 8W

0.1 %

91

Signal-to-Noise Ratio SNR

A-weighted 96

dB

Efficiency η

f = 1kHz

87 %

Left-Right Channel Gain
Matching

P

OUT

= 10W

dB

SYMBOL

THD+N

R

LOAD

R

LOAD

OUT

= 10W

= 8Ω, P

= 8Ω, L > 60µH , P

22Hz to 22kHz

= 15W + 15W ,

OU T

MIN TYP MAX

21.6 22.0 22.3

24.9 25.0 25.6

29.2 29.5 29.9

35.9 36.0 36.6

+80

+90

+100

+110

+120

+129

+139

+150

0.02

MAX9708

20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= ∞, MONO = low (stereo

mode), SHDN = MUTE = high, G1 = low, G2 = high (A

V

= 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are

connected between OUT_+ and OUT_-, unless otherwise stated. T

A

= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 1)

PARAMETER

CONDITIONS

UNITS

Output Short-Circuit Current
Threshold

I

SC

R

LOAD

= 0Ω 2.4 A

Into shutdown -63

Click-and-Pop Level K

CP

Peak voltage, 32
samples/second,

-55

dBV

MONO MODE (R

LOAD

= 4Ω, MONO = High)

MUTE = 1, R

LOAD

= ∞ 20

Quiescent Current

MUTE = 0 5

mA

R

LOAD

= 8Ω 23

Output Power P

OUT

f = 1kHz,

R

LOAD

= 4Ω 42

W

Total Harmonic Distortion Plus
Noise

f = 1kHz, BW = 22Hz to 22kHz,
R

LOAD

= 4Ω, P

OUT

= 17W

%

91

Signal-to-Noise Ratio SNR

R

LOAD

= 4Ω,

P

OUT

= 10W

A-weighted 95

dB

Efficiency η

R

LOAD

= 4Ω, L > 40µH, P

OUT

= 42W,

f = 1kHz

85 %

Output Short-Circuit Current
Threshold

I

SC

R

LOAD

= 0Ω 4.8 A

Into shutdown -60

Click-and-Pop Level K

CP

Peak voltage, 32
samples/second,
A-weighted (Notes 2, 4)

-63

dBV

DIGITAL INPUTS (SHDN, MUTE, G1, G2, FS1, FS2, TH0, TH1, TH2, SYNCIN, MONO)

Logic-Input Current I

IN

0 to 12V 1 µA

Logic-Input High Voltage V

IH

2.5 V

Logic-Input Low Voltage V

IL

0.8 V

OPEN-DRAIN OUTPUTS (TEMP, SYNCOUT)

Open-Drain Output Low Voltage V

OL

I

SINK

= 3mA 0.4 V

Leakage Current I

LEAK

V

PULLUP

= 5.5V 0.2 µA

Note 1: All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design.
Note 2: Inputs AC-coupled to GND.
Note 3: The device is current limited. The maximum output power is obtained with an 8Ω load.
Note 4: Testing performed with an 8Ω resistive load in series with a 68µH inductive load connected across BTL outputs. Mode tran-

sitions are controlled by SHDN.

SYMBOL

MIN TYP MAX

A-weighted (Notes 2, 4)

THD = 10%

Out of shutdown

20Hz to 20kHz

Out of shutdown

0.12

MAX9708

20W/40W, Filterless, Spread-Spectrum,

Mono/Stereo, Class D Amplifier

_______________________________________________________________________________________ 5

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER

MAX9708 toc01

OUTPUT POWER PER CHANNEL (W)

THD+N (%)

252015105

0.1

1

10

100

0.01
030

PVDD = 18V, 8

Ω

STEREO MODE, 1kHz

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER

MAX9708 toc02

OUTPUT POWER PER CHANNEL (W)

THD+N (%)

105

0.1

1

10

100

0.01
015

PVDD = 12V,
STEREO MODE,
f

IN

= 1kHz

RL = 8

Ω

RL = 4

Ω

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY

MAX9708 toc03

FREQUENCY (Hz)

THD+N (%)

10k1k100

0.1

10 100k

1

0.01

PVDD = 18V,
8Ω STEREO MODE,
P

OUT

= 8.3W PER

CHANNEL

EFFICIENCY vs. OUTPUT POWER

MAX9708 toc04

OUTPUT POWER PER CHANNEL (W)

EFFICIENCY (%)

252015105

20

30

40

50

60

70

80

90

100

10

030

PVDD = 18V, 8

Ω

STEREO MODE

OUTPUT POWER

vs. SUPPLY VOLTAGE

MAX9708 toc05

SUPPLY VOLTAGE (V)

OUTPUT POWER PER CHANNEL (W)

161412

5

10

15

20

25

30

0

10 18

RL = 8Ω
STEREO MODE

10% THD+N

1% THD+N

NO-LOAD SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX9708 toc06

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

2018161412

12

14

16

18

20

22

24

10

10 22

STEREO MODE

TA = +25°C

TA = +85°C

TA = -40°C

Typical Operating Characteristics

(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= ∞, SHDN = high, MONO

= low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R

L

) are between OUT_+ and

OUT_-, T

A

= +25°C, unless otherwise stated.)

SHUTDOWN SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX9708 toc07

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (nA)

201812 14 16

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0

10 22

SHDN = 0

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER

MAX9708 toc08

OUTPUT POWER (W)

THD+N (%)

5040302010

0.1

1

10

100

0.01
060

PVDD = 18V, 4Ω MONO MODE,
1kHz

MAX9708

20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier

6 _______________________________________________________________________________________

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY

MAX9708 toc10

FREQUENCY (Hz)

THD+N (%)

10k1k100

0.1

10 100k

1

0.01

PVDD = 18V,
4Ω MONO MODE,
P

OUT

= 18W

WIDEBAND OUTPUT SPECTRUM

(SSM MODE)

MAX9708 toc11

FREQUENCY (Hz)

OUTPUT AMPLITUDE (dBV)

10M1M

-60

-50

-40

-30

-20

-10

0

10

20

30

-70
100k 100M

10kHz RBW

WIDEBAND OUTPUT SPECTRUM

(FFM MODE)

MAX9708 toc12

FREQUENCY (Hz)

OUTPUT AMPLITUDE (dBV)

10M1M100k 100M

10kHz RBW

-60

-50

-40

-30

-20

-10

0

10

20

30

-70

OUTPUT FREQUENCY SPECTRUM

(SSM MODE)

MAX9708 toc13

FREQUENCY (kHz)

OUTPUT AMPLITUDE (dBV)

20161284

-100

-80

-60

-40

-20

0

-120
024

OUTPUT FREQUENCY SPECTRUM

(FFM MODE)

MAX9708 toc14

FREQUENCY (kHz)

OUTPUT AMPLITUDE (dBV)

20161284

-100

-80

-60

-40

-20

0

-120
024

Typical Operating Characteristics (continued)

(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= ∞, SHDN = high, MONO

= low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R

L

) are between OUT_+ and

OUT_-, T

A

= +25°C, unless otherwise stated.)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER

MAX9708 toc09

OUTPUT POWER (W)

THD+N (%)

2015105

0.1

1

10

100

0.01
025

PVDD = 12V,
MONO MODE,
f

IN

= 1kHz

R

L

= 4

Ω

MAX9708

20W/40W, Filterless, Spread-Spectrum,

Mono/Stereo, Class D Amplifier

_______________________________________________________________________________________ 7

EFFICIENCY vs. OUTPUT POWER

MAX9708 toc15

OUTPUT POWER (W)

EFFICIENCY (%)

5040302010

20

30

40

50

60

70

80

90

100

10

060

PVDD = 18V,
4Ω MONO MODE

OUTPUT POWER

vs. SUPPLY VOLTAGE

MAX9708 toc16

SUPPLY VOLTAGE (V)

OUTPUT POWER (W)

161412

10

20

30

40

50

60

0

10 18

RL = 4Ω,
MONO MODE,
10% THD+N

OUTPUT POWER

vs. LOAD RESISTANCE

MAX9708 toc17

LOAD RESISTANCE (Ω)

OUTPUT POWER (W)

1086

10

20

30

40

50

60

0

412

MONO MODE,
10% THD+N,
PV

DD

= 18V

OUTPUT POWER

vs. LOAD RESISTANCE

MAX9708 toc18

LOAD RESISTANCE (Ω)

OUTPUT POWER PER CHANNEL (W)

111098

5

10

15

20

25

30

0

712

STEREO MODE,
10% THD+N,
PV

DD

= 18V

MUTE RESPONSE

MAX9708 toc19

40ms/div

MUTE
5V/div

OUTPUT
50mV/div

SHUTDOWN RESPONSE

MAX9708 toc20

40ms/div

SHDN
5V/div

OUTPUT
50mV/div

Typical Operating Characteristics (continued)

(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= ∞, SHDN = high, MONO

= low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R

L

) are between OUT_+ and

OUT_-, T

A

= +25°C, unless otherwise stated.)

MAX9708

20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier

8 _______________________________________________________________________________________

COMMON-MODE REJECTION RATIO

vs. FREQUENCY

MAX9708 toc21

FREQUENCY (Hz)

CMRR (dB)

10k1k100

-105

-100

-95

-90

-85

-80

-75

-70

-65

-60

-110
10 100k

INPUT REFERRED

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

MAX9708 toc22

FREQUENCY (Hz)

PSRR (dB)

10k1k100

-100

-90

-80

-70

-60

-50

-40

-30

-110
10 100k

CROSSTALK vs. FREQUENCY

MAX9708 toc23

FREQUENCY (Hz)

CROSSTALK (dB)

10k1k100

-110

-100

-90

-80

-70

-60

-50

-40

-120
10 100k

MAXIMUM STEADY-STATE OUTPUT POWER

vs. TEMPERATURE

MAX9708 toc24

AMBIENT TEMPERATURE (°C)

OUTPUT POWER PER CHANNEL (W)

6040

50

5

15

10

25

20

30

35

40

0

30 70

PVDD = 18V, 8

Ω

STEREO MODE, 1kHz,
FS1 = FS2 = 1
TH0 = TH1 = 1
TH2 = 0

MEASURED WITH THE EV KIT (TQFN
PACKAGE), JUNCTION TEMPERATURE
MAINTAINED AT +110°C

MAXIMUM STEADY-STATE OUTPUT POWER

vs. TEMPERATURE

MAX9708 toc25

AMBIENT TEMPERATURE (°C)

OUTPUT POWER (W)

60

40 50

10

20

40

30

50

60

70

0

30 70

PVDD = 18V, 4

Ω

MONO MODE, 1kHz,
FS1 = FS2 = 1
TH0 = TH1 = 1
TH2 = 0

MEASURED WITH THE EV KIT (TQFN
PACKAGE), JUNCTION TEMPERATURE
MAINTAINED AT +110°C

Typical Operating Characteristics (continued)

(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= ∞, SHDN = high, MONO

= low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R

L

) are between OUT_+ and

OUT_-, T

A

= +25°C, unless otherwise stated.)

Pin Description

PIN

TQFP TQFN

NAME FUNCTION

1, 8, 13, 16,
17, 32, 33, 41,
48, 49, 50, 55,

58, 63, 64

1, 12, 42, 43,

44, 55, 56

N.C. No Connection. Not internally connected.

2, 3, 4, 45, 46,

47, 56, 57

2, 3, 4, 39,

PGND Power Ground

5, 6, 7,

42, 43, 44

5, 6, 7,

36, 37, 38

PV

DD

Positive Power Supply. Bypass to PGND with a 0.1µF and a 47µF capacitor with the
smallest capacitor placed as close to pins as possible.

40, 41, 49, 50