MAXIM MAX9709 Technical data

General Description

The MAX9709 stereo/mono, Class D audio power amplifi­er delivers up to 2 x 25W into an 8Ω stereo mode and
1 x 50W into a 4Ω load in mono mode while offering up to
87% efficiency. The MAX9709 provides Class AB amplifi­er performance with the benefits of Class D efficiency,
eliminating the need for a bulky heatsink and conserving
power. The MAX9709 operates from a single +10V to
+22V supply, driving the load in a BTL configuration.

The MAX9709 offers two modulation schemes: a fixed-fre­quency modulation (FFM) mode, and a spread-spectrum
modulation (SSM) mode that reduces EMI-radiated emis­sions. The MAX9709 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 MAX9709 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 25W Output Power in Stereo Mode

(8Ω, THD = 10%)

♦ 1 x 50W Output Power in Mono Mode

(4Ω, THD = 10%)

♦ High Efficiency: Up to 87%
♦ Filterless Class D Amplifier
♦ Unique Patented 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
♦ Clock Synchronization Input and Output
♦ Available in Thermally Efficient, Space-Saving

Packages: 56-Pin TQFN and 64-Pin TQFP

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

________________________________________________________________ Maxim Integrated Products 1

Simplified Block Diagram

Ordering Information

19-3769; Rev 0; 9/05

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

PART TEMP RANGE PIN-PACKAGE

MAX9709ETN+ -40°C to +85°C 56 TQFN-EP** T5688-3

MAX9709ECB+* -40°C to +85°C 64 TQFP-EP** C64E-6

PKG

CODE

FS1, FS2

SYNC

RIGHT

CHANNEL

LEFT

CHANNEL

MONO

G1, G2

TH0, TH1,

TH2

2

CLASS D

GAIN

CONTROL

2

MODULATOR

STEREO MODE

3

MAX9709

OUTPUT

PROTECTION

SYNCOUT

TEMP

FS1, FS2

SYNC

AUDIO

INPUT

V

G1, G2

TH0, TH1,

TH2

DIGITAL

MONO

2

CLASS D

GAIN

CONTROL

2

MODULATOR

MONO MODE

MAX9709

OUTPUT

PROTECTION

3

SYNCOUT

TEMP

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(PVDD= VDD= +20V, 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)

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 SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Voltage Range V

Shutdown Current I

Shutdown to Full Operation t

Mute to Full Operation t

Input Impedance R

Output Pulldown Resistance SHDN = GND 600 kΩ

Output Offset Voltage V

Power-Supply Rejection Ratio PSRR

Common-Mode Rejection Ratio CMRR

Switch On-Resistance R

Switching Frequency f

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

SYNCIN Lock Range Equal to fSW x 4 600 1200 kHz

DD

SHDN

SON

MUTE

IN

OS

DS

SW

Inferred from PSRR test 10 22 V
SHDN = low 0.1 1 µA

G1 = 0, G2 = 1 50 85 125

G1 = 1, G2 = 1 40 63 90

G1 = 1, G2 = 0 25 43 60

G1 = 0, G2 = 0 12 21 30

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

PVDD = 10V to 22V 67 90

200mV

P-P

(Note 2)

DC, input referred 49 70

f = 20Hz to 20kHz, input referred 60

One power switch 0.3 0.6 Ω

FS1 FS2

0 0 180 200 220

1 1 (SSM) 200

1 0 160

0 1 250

= 1kHz 90

= 20kHz 52

ripple

f

RIPPLE

f

RIPPLE

100 ms

100 ms

3 ±40 mV

kΩ

dB

dB

kHz

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(PVDD= VDD= +20V, 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 SYMBOL CONDITIONS MIN TYP MAX UNITS

Gain A

TEMP Flag Threshold T

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

STEREO MODE (R

Quiescent Current

Output Power P

Total Harmonic Distortion Plus
Noise

Signal-to-Noise Ratio SNR P

Efficiency η P

Left-Right Channel Gain
Matching

= 8Ω, Note 3)

LOAD

V

FLAG

OUT

THD+N

G1 = 0, G2 = 1 21.6 22.0 22.3

G1 = 1, G2 = 1 24.9 25.0 25.6

G1 = 1, G2 = 0 29.2 29.5 29.9

G1 = 0, G2 = 0 35.9 36.0 36.6

TH2 TH1 TH0

000 80

001 90

0 1 0 100

0 1 1 110

1 0 0 120

1 0 1 129

1 1 0 139

111

MUTE = 1, R
MUTE = 0 6.5 13

f = 1kHz, THD =
10%, T

A

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

= 12W

OUT

= 10W

OUT

= 25W + 25W , f = 1kHz 87 %

OU T

R

= ∞ 0.2 %

LOAD

= 20V 25

= 22V 29

= 12V,

= 4Ω

22Hz to 22kHz 91

A-weighted 96

LOAD

= +25°C

= ∞ 20 33

P

VDD

P

VDD

P

VDD

R

LOAD

15

0.1 %

dB

°C

mA

W

dB

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(PVDD= VDD= +20V, 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)

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: Testing performed with an 8Ω resistive load in series with a 68µH inductive load across the BTL outputs.
Note 4: Minimum output power is guaranteed by pulse testing.
Note 5: 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.

Note 6: Testing performed with a 4Ω resistive load in series with a 33µH inductive load across the BTL outputs.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Output Short-Circuit Current
Threshold

Click-and-Pop Level K

MONO MODE (R

Quiescent Current

Output Power P

Total Harmonic Distortion Plus
Noise

Signal-to-Noise Ratio SNR P

Efficiency η P

= 4Ω, MONO = HIGH) (Note 6)

LOAD

I

SC

CP

OUT

THD+N

R

LOAD

Peak voltage, 32
samples/second,
A-weighted (Notes 2, 5)

MUTE = 1, R
MUTE = 0 6.5

f = 1kHz,
THD = 10%

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

= 22W

P

OUT

= 10W

OUT

= 54W, f = 1kHz 86 %

OUT

= 0Ω 3A

= ∞ 20

LOAD

R

= 8Ω 25

LOAD

= 4Ω 50

R

LOAD

Into shutdown -63

Out of shutdown -55

20Hz to 20kHz 91

A-weighted 95

0.09 %

dBV

mA

W

dB

Output Short-Circuit Current
Threshold

Click-and-Pop Level K

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

Logic-Input Current I

Logic-Input High Voltage V

Logic-Input Low Voltage V

OPEN-DRAIN OUTPUTS (TEMP, SYNCOUT)

Open-Drain Output Low Voltage V

Leakage Current I

I

SC

CP

IN

IH

IL

OL

LEAK

R

= 0Ω 6A

LOAD

Peak voltage, 32
samples/second,
A-weighted (Notes 2, 5)

0 to 12V 1 µA

I

= 3mA 0.4 V

SINK

V

= 5.5V 0.2 µA

PULLUP

Into shutdown -60

dBV

Out of shutdown -63

2.5 V

0.8 V

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

_______________________________________________________________________________________ 5

Typical Operating Characteristics

(PVDD= VDD= +20V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= 8Ω, 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

MAX9709 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 (MONO MODE)

MAX9709 toc08

OUTPUT POWER (W)

THD+N (%)

5040302010

0.1

1

10

100

0.01
060

R

LOAD

= 4

Ω

f

IN

= 1kHz

THD+N (%)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER (STEREO MODE)

100

fIN = 1kHz

10

1

0.1

0.01
035

OUTPUT POWER (W)

MAX9709 toc01

30252015105

EFFICIENCY vs. OUTPUT POWER

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER (STEREO MODE)

100

PVDD = 12V

10

1

THD+N (%)

0.1

0.01
025

OUTPUT POWER vs. SUPPLY VOLTAGE

(STEREO MODE)

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

030

OUTPUT POWER (W)

252015105

MAX9709 toc04

OUTPUT POWER (W)

35

30

25

20

15

10

5

0

10 24

Ω

R

= 8

LOAD

Ω

R

= 4

LOAD

2015105

OUTPUT POWER (W)

(STEREO MODE)

THD+N = 10%

THD+N = 1%

222018161412

SUPPLY VOLTAGE (V)

MAX9709 toc02

0.1

THD+N (%)

0.01

24

22

MAX9709 toc05

20

18

16

SUPPLY CURRENT (mA)

14

12

10

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY (STEREO MODE)

1

P

= 12W

OUT

10 100k

NO-LOAD SUPPLY CURRENT

vs. SUPPLY VOLTAGE (STEREO MODE)

TA = +85°C

10 22

10k1k100

FREQUENCY (Hz)

TA = +25°C

TA = -40°C

2018161412

SUPPLY VOLTAGE (V)

MAX9709 toc03

MAX9709 toc06

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(PVDD= VDD= +20V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= 8Ω, 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

MAX9709 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

WIDEBAND OUTPUT SPECTRUM

30

20

10

0

-10

-20

-30

-40

OUTPUT AMPLITUDE (dBV)

-50

-60

-70

(FFM MODE)

FREQUENCY (Hz)

10kHz RBW

10M1M100k 100M

TOTAL HARMONIC DISTORTION PLUS NOISE

1

0.1

THD+N (%)

0.01
10 100k

0

-20

MAX9709 toc12

-40

-60

-80

OUTPUT AMPLITUDE (dBV)

-100

-120
024

vs. FREQUENCY (MONO MODE)

Ω

R

= 4

LOAD

= 22W

P

OUT

10k1k100

FREQUENCY (Hz)

OUTPUT FREQUENCY SPECTRUM

(SSM MODE)

FREQUENCY (kHz)

WIDEBAND OUTPUT SPECTRUM

(SSM MODE)

30

20

MAX9709 toc10

10

0

-10

-20

-30

-40

OUTPUT AMPLITUDE (dBV)

-50

-60

-70
100k 100M

FREQUENCY (Hz)

10kHz RBW

MAX9709 toc11

10M1M

OUTPUT FREQUENCY SPECTRUM

(FFM MODE)

0

-20

MAX9709 toc13

-40

-60

-80

OUTPUT AMPLITUDE (dBV)

-100

20161284

-120
024

FREQUENCY (kHz)

MAX9709 toc14

20161284

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(PVDD= VDD= +20V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= 8Ω, 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.)

EFFICIENCY vs. OUTPUT POWER

OUTPUT POWER vs. SUPPLY VOLTAGE

(MONO MODE)

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

060

R

LOAD

Ω

= 4

OUTPUT POWER (W)

5040302010

70

60

MAX9709 toc15

50

40

30

OUTPUT POWER (W)

20

10

R

LOAD

= 1kHz

f

IN

0

10 24

OUTPUT POWER vs. LOAD RESISTANCE

(STEREO MODE)

30

25

THD+N = 10%

= 1kHz

f

IN

MAX9709 toc18

(MONO MODE)

Ω

= 4

THD+N = 10%

THD+N = 1%

222018161412

SUPPLY VOLTAGE (V)

MUTE RESPONSE

MAX9709 toc19

MAX9709 toc16

MUTE
5V/div

OUTPUT POWER vs. LOAD RESISTANCE

60

50

40

30

20

OUTPUT POWER (W)

10

0

412

(MONO MODE)

THD+N = 10%

= 1kHz

f

IN

1086

LOAD RESISTANCE (Ω)

SHUTDOWN RESPONSE

MAX9709 toc20

MAX9709 toc17

SHDN
5V/div

20

15

10

OUTPUT POWER PER CHANNEL (W)

5

0

716

LOAD RESISTANCE (Ω)

15141312111098

40ms/div

OUTPUT
50mV/div

40ms/div

OUTPUT
50mV/div

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(PVDD= VDD= +20V, PGND = GND = 0V, CSS= 0.47µF, C

REG

= 0.01µF, C1 = 0.1µF, C2 = 1µF, R

LOAD

= 8Ω, 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

COMMON-MODE REJECTION RATIO

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

-60
INPUT REFERRED

-65

-70

-75

-80

-85

CMRR (dB)

-90

-95

-100

-105

-110
10 100k

FREQUENCY (Hz)

10k1k100

MAX9709 toc21

-30

-40

-50

-60

-70

PSRR (dB)

-80

-90

-100

-110
10 100k

vs. FREQUENCY

MAX9709 toc22

10k1k100

FREQUENCY (Hz)

-40

-50

-60

-70

-80

-90

CROSSTALK (dB)

-100

-110

-120

CROSSTALK vs. FREQUENCY

10 100k

FREQUENCY (Hz)

10k1k100

MAX9709 toc23

35

30

25

20

15

10

OUTPUT POWER PER CHANNEL (W)

5

0

PIN

TQFP TQFN

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

58, 63, 64

2, 3, 4, 45, 46,

47, 56, 57

5, 6, 7,

42, 43, 44

MAXIMUM STEADY-STATE OUTPUT POWER

vs. TEMPERATURE (STEREO MODE)

fIN = 1kHz
TH0 = TH1 = 1
TH2 = 0

30 70

AMBIENT TEMPERATURE (°C)

605040

NAME FUNCTION

1, 12, 42, 43,

44, 55, 56

2, 3, 4, 39,

40, 41, 49, 50

5, 6, 7,

36, 37, 38

N.C. No Connection. Not internally connected.

PGND Power Ground

PV

Positive Power Supply. Bypass to PGND with a 0.1µF and a 47µF capacitor with the

DD

smallest capacitor placed as close to pins as possible.

MAX9709 toc24

MAXIMUM STEADY-STATE OUTPUT POWER

vs. TEMPERATURE (MONO MODE)*

70

60

50

40

30

OUTPUT POWER (W)

20

R

= 4

Ω

LOAD

f

= 1kHz

IN

10

TH0 = TH1 = 1
TH2 = 0

0

30

AMBIENT TEMPERATURE (°C)

*MEASURED WITH THE MAX9709EVKIT,
JUNCTION TEMPERATURE MAINTAINED AT +110°C.

605040

MAX9709 toc25

70

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

_______________________________________________________________________________________ 9

Pin Description (continued)

PIN

TQFP TQFN

9 8 C1N Charge-Pump Flying Capacitor C1, Negative Terminal

10 9 C1P Charge-Pump Flying Capacitor C1, Positive Terminal

11 10 CPV

12 11 SYNCOUT Open-Drain Slew-Rate-Limited Clock Output. Pullup with a 10kΩ to resistor to REG.

14 13 SYNCIN

15 14 FS2 Frequency Select 2

18 15 FS1 Frequency Select 1

19 16 INL- Left-Channel Negative Input (Stereo Mode Only)

20 17 INL+ Left-Channel Positive Input (Stereo Mode Only)

21 18 MONO

22, 23, 24 19, 20, 21 REG Internal Regulator Output Voltage (6V). Bypass with a 0.01µF capacitor to GND.

25, 26 22, 23 GND Analog Ground

27 24 SS Soft-Start. Connect a 0.47µF capacitor to GND to utilize soft-start power-up sequence.

28 25 V

29 26 INR- Right-Channel Negative Input. In mono mode, INR- is the negative input.

30 27 INR+ Right-Channel Positive Input. In mono mode, INR+ is the positive input.

31 28 G1 Gain Select input 1

34 29 G2 Gain Select input 2

35 30 SHDN

36 31 MUTE

37 32 TEMP Thermal Flag Output, Open Drain. Pullup with a 10kΩ resistor to REG.

38 33 TH2 Temperature Flag Threshold Select Input 2

39 34 TH1 Temperature Flag Threshold Select Input 1

40 35 TH0 Temperature Flag Threshold Select Input 0

51, 52 45, 46 OUTR- Right-Channel Negative Output

53, 54 47, 48 OUTR+ Right-Channel Positive Output

59, 60 51, 52 OUTL- Left-Channel Negative Output

61, 62 53, 54 OUTL+ Left-Channel Positive Output

EP EP GND Exposed Paddle. Connect to GND with multiple vias for best heat dissipation.

NAME FUNCTION

Charge-Pump Power Supply. Bypass to PVDD with a 1µF capacitor as close to pin as

DD

possible.

Clock Synchronization Input. Allows for synchronization of the internal oscillator with an
external clock.

Mono/Stereo Mode Input. Drive logic high for mono mode. Drive logic low for stereo
mode.

Analog Power Supply. Bypass to GND with a 0.1µF capacitor as close to pin as

DD

possible.

Active-Low Shutdown Input. Drive SHDN high for normal operation. Drive SHDN low to
place the device in shutdown mode.

Active-Low Mute Input. Drive logic low to place the device in mute. In mute mode,
Class D output stage is no longer switching. Drive high for normal operation. MUTE is
internally pulled up to V

with a100kΩ resistor.

REG

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

10 ______________________________________________________________________________________

Typical Application Circuits/Functional Diagrams

Figure 1. Typical Application and Functional Diagram in Stereo Mode

LEFT

V

DIGITAL

V

+

-

+

-

CHANNEL

RIGHT

CHANNEL

DIGITAL

1µF

1µF

1µF

1µF

15 (18)

14 (15)

13 (14)

17 (20)

16 (19)

27 (30)

26 (29)

30 (35)

31 (36)

28 (31)

29 (34)

18 (21)

FS1

FS2

SYNCIN

INL+

INL-

INR+

INR-

SHDN

MUTE
G2

G1

MONO

5–7, 36–38

MUX

PV

DD

PV

DD

47µF*

PGND

PV

CLASS D

MODULATOR

AND H-BRIDGE

PV

CLASS D

MODULATOR

AND H-BRIDGE

CHARGE

PUMP

REGULATOR

2–4, 39–41, 49–50
(2–4, 45–47, 56–57)

SYNCOUT

DD

OUTL+

OUTL-

DD

OUTR+

OUTR-

CPV

DD

C1P

C1N

REG

TEMP

V

DIGITAL

10kΩ

11 (12)

53, 54 (61, 62)

51, 52 (59, 60)

47, 48 (53, 54)

45, 46 (51, 52)

C2

1µF

10 (11)

9 (10)

C1

0.1µF

8 (9)

19, 20, 21 (22, 23, 24)

32 (37)

PV

DD

C

REG

0.01µF

V

DD

0.1µF

22, 23

(25, 26)

V

GND

R

IN

R

IN

R

IN

R

IN

CONTROL

GAIN

CONTROL

DD

R

F

V

BIAS

R

F

R

F

V

BIAS

R

F

THERMAL SENSOR

(5–7, 42–44)25 (28)

MAX9709

24 (27)

SS

C

SS

0.47µF

V

DIGITAL

TH0 TH1 TH2

35 (40) 34 (39) 33 (38)

V

DIGITAL

CONFIGURATION: TQFN STEREO MODE, SSM, INTERNAL OSCILLATOR, GAIN = 22dB, THERMAL SETTING = +120°C

( ) TQFP PACKAGE
*ADDITIONAL BULK CAPACITANCE

10kΩ

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

______________________________________________________________________________________ 11

Typical Application Circuits/Functional Diagrams (continued)

Figure 2. Typical Application and Functional Diagram in Mono Mode

AUDIO

INPUT

V

DIGITAL

V

DIGITAL

5–7, 36–38

MUX

PV

PV

DD

47µF*

0.1µF

DD

2–4, 39–41, 49–50
(2–4, 45–47, 56–57)

PGND

PV

DD

CLASS D

MODULATOR

AND H-BRIDGE

PV

DD

CLASS D

MODULATOR

AND H-BRIDGE

CHARGE

PUMP

REGULATOR

SYNCOUT

OUTL+

OUTL-

OUTR+

OUTR-

CPV

C1P

C1N

REG

TEMP

V

DIGITAL

11 (12)

53, 54 (61, 62)

51, 52 (59, 60)

47, 48 (53, 54)

45, 46 (51, 52)

10 (11)

DD

9 (10)

8 (9)

19, 20, 21 (22, 23, 24)

32 (37)

10kΩ

C2

1µF

C1

0.1µF

PV

DD

C

REG

0.01µF

V

DD

0.1µF

22, 23

V

DIGITAL

FS1

15 (18)
14 (15)

FS2

13 (14)

SYNCIN

1µF

17 (20)

16 (19)

30 (35)

31 (36)

28 (31)

29 (34)

18 (21)

INR+

INR-

SHDN

MUTE
G1

G2

MONO

+

1µF

-

(25, 26)

V

GND

R

IN

R

IN

CONTROL

GAIN

CONTROL

DD

R

F

V

BIAS

R

F

THERMAL SENSOR

(5–7, 42–44)25 (28)

MAX9709

TH0 TH1 TH2

35 (40) 34 (39) 33 (38)

V

DIGITAL

CONFIGURATION: TQFN MONO MODE, SSM, INTERNAL OSCILLATOR, GAIN = 22dB, THERMAL SETTING = +120°C

( ) TQFP PACKAGE
*ADDITIONAL BULK CAPACITANCE

24 (27)

V

DIGITAL

10kΩ

SS

C

SS

0.47µF

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

12 ______________________________________________________________________________________

Detailed Description

The MAX9709 filterless, Class D audio power amplifier
features several improvements to switch mode amplifi­er technology. The MAX9709 is a two-channel, stereo
amplifier with 25W output power on each channel. The
amplifier can be configured to output 50W output
power in mono mode. The device offers Class AB per­formance with Class D efficiency, while occupying min­imal board space. A unique filterless modulation
scheme and spread-spectrum switching mode create a
compact, flexible, low-noise, efficient audio power
amplifier. The differential input architecture reduces
common-mode noise pickup, and can be used without
input-coupling capacitors. The device can also be con­figured as a single-ended input amplifier.

Mono/Stereo Configuration

The MAX9709 features a mono mode that allows the
right and left channels to operate in parallel, achieving
up to 50W of output power. The mono mode is enabled
by applying logic high to MONO. In this mode, audio
signal applied to the right channel (INR+/INR-) is rout­ed to the H-bridge of both channels, while signal
applied to the left channel (INL+/INL-) is ignored.
OUTL+ must be connected to OUTR+ and OUTL- must
be connected to OUTR- using heavy PC board traces
as close to the device as possible (see Figure 2).

When the device is placed in mono mode on a PC
board with outputs wired together, ensure that the
MONO pin can never be driven low when the device is
enabled. Driving the MONO pin low (stereo mode)
while the outputs are wired together in mono mode may
trigger the short-circuit or thermal protection or both,
and may even damage the device.

Efficiency

Efficiency of a Class D amplifier is attributed to the
region of operation of the output stage transistors. In a
Class D amplifier, the output transistors act as current­steering 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

powers. Under normal operating levels (typical music
reproduction levels), efficiency falls below 30%, where­as the MAX9709 still exhibits 87% efficiency under the
same conditions.

Shutdown

The MAX9709 features a shutdown mode that reduces
power consumption and extends battery life. Driving
SHDN low places the device in low-power (0.1µA) shut­down mode. Connect SHDN to digital high for normal
operation.

Mute Function

The MAX9709 features a clickless/popless mute mode.
When the device is muted, the outputs stop switching,
muting the speaker. Mute only affects the output stage
and does not shut down the device. To mute the
MAX9709, drive MUTE to logic low. Driving MUTE low
during the power-up/down or shutdown/turn-on cycle
optimizes click-and-pop suppression.

Click-and-Pop Suppression

The MAX9709 features comprehensive click-and-pop
suppression that eliminates audible transients on start­up and shutdown. While in shutdown, the H-bridge is
pulled to GND through a 330kΩ resistor. During startup
or power-up, the input amplifiers are muted and an
internal loop sets the modulator bias voltages to the
correct levels, preventing clicks and pops when the H­bridge is subsequently enabled. Following startup, a
soft-start function gradually unmutes the input ampli­fiers. The value of the soft-start capacitor has an impact
on the click-and-pop levels, as well as startup time.

Thermal Sensor

The MAX9709 features an on-chip temperature sensor
that monitors the die temperature. When the junction
temperature exceeds a programmed level, TEMP is
pulled low. This flags the user to reduce power or shut
down the device. TEMP may be connected to SS or

MUTE for automatic shutdown during overheating. If
TEMP is connected to MUTE, during thermal protection

mode, the audio is muted and the device is in mute
mode. If TEMP is connected to SS, during thermal pro­tection mode, the device is shut down but the thermal
sensor is still active.

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

______________________________________________________________________________________ 13

TEMP returns high once the junction temperature cools
below the set threshold minus the thermal hysteresis. If
TEMP is connected to either MUTE or SS, the audio
output resumes. The temperature threshold is set by
the TH0, TH1, and TH2 inputs as shown in Table 1. An
RC filter may be used to eliminate any transient at the
TEMP output as shown in Figure 3.

If TH2 = TH1 = TH0 = HIGH, it is likely that the MAX9709
enters thermal shutdown without tripping the thermal
flag.

Gain Selection

The MAX9709 features four pin-selectable gain settings;
see Table 2.

Operating Modes

Fixed-Frequency Modulation (FFM) Mode

The MAX9709 features three switching frequencies in
the FFM mode (Table 3). In this mode, the frequency
spectrum of the Class D output consists of the funda­mental switching frequency and its associated harmon­ics (see the Wideband Output Spectrum graph in the
Typical Operating Characteristics). Select one of the
three fixed switching frequencies such that the harmon­ics do not fall in a sensitive band. The switching fre­quency can be changed any time without affecting
audio reproduction.

Spread-Spectrum Modulation (SSM) Mode

The MAX9709 features a unique, patented spread­spectrum (SSM) mode that flattens the wideband spec­tral components, improving EMI emissions that may be
radiated by the speaker and cables. This mode is
enabled by setting FS1 = FS2 = high. In SSM mode, the
switching frequency varies randomly by ±4% around
the center frequency (200kHz). The modulation scheme
remains the same, but the period of the triangle wave­form changes from cycle to cycle. Instead of a large
amount of spectral energy present at multiples of the
switching frequency, the energy is now spread over a
bandwidth that increases with frequency. Above a few
megahertz, the wideband spectrum looks like white
noise for EMI purposes. SSM mode reduces EMI com­pared to fixed-frequency mode. This can also help to
randomize visual artifacts caused by radiated or supply
borne interference in displays.

Synchronous Switching Mode

The MAX9709 SYNCIN input allows the Class D amplifi­er to switch at a frequency defined by an external clock
frequency. Synchronizing the amplifier with an external
clock source may confine the switching frequency to a
less sensitive band. The external clock frequency range
is from 600kHz to 1.2MHz and can have any duty cycle,
but the minimum pulse must be greater than 100ns.

SYNCOUT is an open-drain clock output for synchro­nizing external circuitry. Its frequency is four times the
amplifier’s switching frequency and it is active in either
internal or external oscillator mode.

Figure 3. An RC Filter Eliminates Transient During Switching

Table 1. MAX9709 Junction Temperature
Threshold Setting

Table 2. MAX9709 Gain Setting

Table 3. Switching Frequencies

V

DIGITAL

10kΩ

TEMP

10kΩ

0.1µF

TO DIGITAL
INPUT

JUNCTION

TEMPERATURE

(°C)

80 Low Low Low

90 Low Low High

100 Low High Low

110 Low High High

120 High Low Low

129 High Low High

139 High High Low

158 High High High

TH2 TH1 TH0

G1 G2 GAIN (dB)

Low High 22

High High 25

High Low 29.5

Low Low 36

FS1 FS2

0 0 200 Fixed-frequency

0 1 250 Fixed-frequency

1 0 160 Fixed-frequency

1 1 200 ±4 Spread-spectrum

SYNCOUT

FREQUENCY (kHz)

MODULATION

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

14 ______________________________________________________________________________________

Linear Regulator (REG)

The supply voltage range for the MAX9709 is from 10V
to 22V to achieve high-output power. An internal linear
regulator reduces this voltage to 6.3V for use with
small-signal and digital circuitry that does not require
high-voltage supply. Bypass a 0.01µF capacitor from
REG to GND.

Applications Information

Logic Inputs

All of the digital logic inputs and output have an
absolute maximum rating of +12V. If the MAX9709 is
operating with a supply voltage between 10V and 12V,
digital inputs can be connected to PVDDor VDD. If
PVDDand VDDare greater than 12V, digital inputs and
outputs must be connected to a digital system supply
lower than 12V.

Input Amplifier

Differential Input

The MAX9709 features a differential input structure,
making them compatible with many CODECs, and
offering improved noise immunity over a single-ended
input amplifier. In devices such as flat-panel displays,
noisy digital signals can be picked up by the amplifier’s
inputs. These signals appear at the amplifiers’ inputs as
common-mode noise. A differential input amplifier
amplifies only the difference of the two inputs, while any
signal common to both inputs is attenuated.

Single-Ended Input

The MAX9709 can be configured as a single-ended
input amplifier by capacitively coupling either input to
GND and driving the other input (Figure 4).

Component Selection

Input Filter

An input capacitor, CIN, in conjunction with the input
impedance of the MAX9709, forms a highpass filter that
removes the DC bias from an incoming signal. The AC­coupling 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:

Choose C

IN

so that f

-3dB

is well below the lowest fre-

quency of interest. Setting f

-3dB

too high affects the
low-frequency response of the amplifier. Use capaci­tors with dielectrics that have low-voltage coefficients,
such as tantalum or aluminum electrolytic. Capacitors
with high-voltage coefficients, such as ceramics, may
result in increased distortion at low frequencies.

Output Filter

The MAX9709 does not require an output filter.
However, output filtering can be used if a design is fail­ing radiated emissions due to board layout or cable
length, or the circuit is near EMI-sensitive devices. See
the MAX9709 evaluation kit for suggested filter topolo­gies. The tuning and component selection of the filter
should be optimized for the load. A purely resistive load
(8Ω) used for lab testing requires different components
than a real, complex load-speaker load.

Charge-Pump Capacitor Selection

The MAX9709 has an internal charge-pump converter
that produces a voltage level for internal circuitry. It
requires a flying capacitor (C1) and a holding capacitor
(C2). 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. The
capacitors’ voltage rating must be greater than 36V.

Figure 4. Single-Ended Input Connections

1µF

INR+

MAX9709

f

=

dB

−

3

2 π

1

RC

IN IN

INR-

1µF

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

______________________________________________________________________________________ 15

Sharing Input Sources

In certain systems, a single audio source can be
shared by multiple devices (speaker and headphone
amplifiers). When sharing inputs, it is common to mute
the unused device, rather than completely shutting it
down. This prevents the unused device inputs from dis­torting the input signal. Mute the MAX9709 by driving
MUTE low. Driving MUTE low turns off the Class D out­put stage, but does not affect the input bias levels of
the MAX9709.

Frequency Synchronization

The MAX9709 outputs up to 27W on each channel in
stereo mode. If higher output power or a 2.1 solution is
needed, two MAX9709s can be used. Each MAX9709
is synchronized by connecting SYNCOUT from the first
MAX9709 to SYNCIN of the second MAX9709 (see
Figure 5).

Supply Bypassing/Layout

Proper power-supply bypassing ensures low distortion
operation. For optimum performance, bypass PVDDto
PGND with a 0.1µF capacitor as close to each PV

DD

pin as possible. A low-impedance, high-current power­supply connection to PVDDis assumed. Additional bulk
capacitance should be added, as required, depending
on the application and power-supply characteristics.
GND and PGND should be star-connected to system
ground. For the TQFN package, solder the exposed
paddle (EP) to the ground plane using multiple-plated
through-hole vias. The exposed paddle must be sol­dered to the ground plane for rated power dissipation
and good ground return. Use wider PC board traces to
lower the parasitic resistance for the high-power output
pins (OUTR+, OUTR-, OUTL+, OUTL-). Refer to the
MAX9709 evaluation kit for layout guidance.

Thermal Considerations

Class D amplifiers provide much better efficiency and
thermal performance than a comparable Class AB
amplifier. However, the system’s thermal performance
must be considered with realistic expectations along
with its many parameters.

Continuous Sine Wave vs. Music

When a Class D amplifier is evaluated in the lab, often
a continuous sine wave is used as the signal source.
While this is convenient for measurement purposes, it
represents a worst-case scenario for thermal loading
on the amplifier. It is not uncommon for a Class D
amplifier to enter thermal shutdown if driven near maxi­mum output power with a continuous sine wave. The
PC board must be optimized for best dissipation (see
the PC Board Thermal Considerations section).

Audio content, both music and voice, has a much lower
RMS value relative to its peak output power. Therefore,
while an audio signal may reach similar peaks as a
continuous sine wave, the actual thermal impact on the
Class D amplifier is highly reduced. If the thermal per­formance of a system is being evaluated, it is important
to use actual audio signals instead of sine waves for
testing. If sine waves must be used, the thermal perfor­mance is less than the system’s actual capability for
real music or voice.

PC Board Thermal Considerations

The exposed pad is the primary route for conducting
heat away from the IC. With a bottom-side exposed
pad, the PC board and its copper becomes the primary
heatsink for the Class D amplifier. Solder the exposed
pad to a copper polygon. Add as much copper as pos­sible from this polygon to any adjacent pin on the Class
D amplifier as well as to any adjacent components, pro­vided these connections are at the same potential.
These copper paths must be as wide as possible. Each
of these paths contributes to the overall thermal capa­bilities of the system.

The copper polygon to which the exposed pad is
attached should have multiple vias to the opposite side
of the PC board, where they connect to another copper
polygon. Make this polygon as large as possible within
the system’s constraints for signal routing.

Additional improvements are possible if all the traces
from the device are made as wide as possible.
Although the IC pins are not the primary thermal path
out of the package, they do provide a small amount.
The total improvement would not exceed about 10%,
but it could make the difference between acceptable
performance and thermal problems.

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

16 ______________________________________________________________________________________

Auxiliary Heatsinking

If operating in higher ambient temperatures, it is possible
to improve the thermal performance of a PC board with
the addition of an external heatsink. The thermal resis­tance to this heatsink must be kept as low as possible to
maximize its performance. With a bottom-side exposed
pad, the lowest resistance thermal path is on the bottom
of the PC board. The topside of the IC is not a significant
thermal path for the device, and therefore is not a cost­effective location for a heatsink. If an LC filter is used in
the design, placing the inductor in close proximity to the
IC can help draw heat away from the MAX9709.

Thermal Calculations

The die temperature of a Class D amplifier can be esti­mated with some basic calculations. For example, the
die temperature is calculated for the below conditions:

•T

A

= +40°C

•P

OUT

= 16W

• Efficiency (η) = 87%

• θ

JA

= 21°C/W

First, the Class D amplifier’s power dissipation must be
calculated:

Then the power dissipation is used to calculate the die
temperature, TC, as follows:

Load Impedance

The on-resistance of the MOSFET output stage in Class
D amplifiers affects both the efficiency and the peak-cur­rent capability. Reducing the peak current into the load
reduces the I

2

R losses in the MOSFETs, which increases
efficiency. To keep the peak currents lower, choose the
highest impedance speaker which can still deliver the
desired output power within the voltage swing limits of
the Class D amplifier and its supply voltage.

Another consideration is the load impedance across
the audio frequency band. A loudspeaker is a complex
electromechanical system with a variety of resonance.
In other words, an 8Ω speaker usually has 8Ω imped-
ance within a very narrow range. This often extends
well below 8Ω, reducing the thermal efficiency below
what is expected. This lower-than-expected impedance
can be further reduced when a crossover network is
used in a multidriver audio system.

Systems Application Circuit

The MAX9709 can be configured into multiple amplifier
systems. One concept is a 2.1 audio system (Figure 5)
where a stereo audio source is split into three channels.
The left- and right-channel inputs are highpass filtered
to remove the bass content, and then amplified by the
MAX9709 in stereo mode. Also, the left- and right-chan­nel inputs are summed together and lowpass filtered to
remove the high-frequency content, then amplified by a
second MAX9709 in mono mode.

The conceptual drawing of Figure 5 can be applied to
either single-ended or differential systems. Figure 6
illustrates the circuitry required to implement a fully
differential filtering system. By maintaining a fully differ­ential path, the signal-to-noise ratio remains uncompro­mised and noise pickup is kept very low. However,
keeping a fully differential signal path results in almost
twice the component count, and therefore performance
must be weighed against cost and size.

The highpass and lowpass filters should have different
cutoff frequencies to ensure an equal power response
at the crossover frequency. The filters should be at

-6dB amplitude at the crossover frequency, which is
known as a Linkwitz-Riley alignment. In the example
circuit of Figure 6, the -3dB cutoff frequency for the
highpass filters is 250Hz, and the -3dB cutoff frequency
for the lowpass filter is 160Hz. Both the highpass filters
and the lowpass filters are at a -6dB amplitude at
approximately 200Hz. If the filters were to have the
same -3dB cutoff frequency, a measurement of sound
pressure level (SPL) vs. frequency would have a peak
at the crossover frequency.

TTP C W CW C

P

P

DISS

=+ × =°+ ×° = °θ 40 24 21 90 4/.

C A DISS JA

OUT

===−−

P

η

OUT

16

W

WW

16 2 4

.

087

.

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

______________________________________________________________________________________ 17

The circuit in Figure 6 uses inverting amplifiers for their
ease in biasing. Note the phase labeling at the outputs
has been reversed. The resistors should be 1% or better
in tolerance and the capacitors 5% tolerance or better.
Mismatch in the components can cause discrepancies
between the nominal transfer function and actual perfor­mance. Also, the mismatch of the input resistors (R15,
R17, R19, and R21 in Figure 6) of the summing amplifier
and lowpass filter causes some high-frequency sound to
be sent to the subwoofer.

The circuit in Figure 6 drives a pair of MAX9709 devices
similar to the circuit in Figure 5. The inputs to the
MAX9709 still require AC-coupling to prevent compro­mising the click-and-pop performance of the MAX9709.

The left and right drivers should be at an 8Ω to 12Ω
impedance, whereas the subwoofer can be 4Ω to 8Ω
depending on the desired output power, the available
power-supply voltage, and the sensitivity of the individ­ual speakers in the system. The four gain settings of
the MAX9709 allow gain adjustments to match the sen­sitivity of the speakers.

Figure 5. Multiple Amplifiers Implement a 2.1 Audio System

RIGHT

AUDIO

LEFT

AUDIO

HIGHPASS

FILTER

HIGHPASS

FILTER

INR+
INR-

MONO

INL+

INL-

SYNCOUT

OUTR+

OUTR-

MAX9709

OUTL+

OUTL-

8Ω
FULL­RANGE
SPEAKER

8Ω
FULL­RANGE
SPEAKER

LOWPASS

Σ

FILTER

V

DIGITAL

SYNCIN

INR+
INR-

MONO

INL+

INL-

MAX9709

OUTR+

OUTR-

OUTL+

OUTL-

4Ω OR 8Ω
WOOFER

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

18 ______________________________________________________________________________________

Figure 6. Fully Differential Crossover Filters

R1

56.2k

Ω

R2, 56.2k

U1A

MAX4478

R6, 56.2k

U1B

MAX4478

R9, 56.2k

U1C

MAX4478

R13, 56.2k

U1D

MAX4478

C9, 47nF

U2A

MAX4478

C11, 47nF

U2B

MAX4478

Ω

Ω

Ω

8

Ω

14

1

7

RIGHT
AUDIO
INPUT

LEFT

AUDIO

INPUT

NOTE:
OP AMP POWER PINS OMITTED FOR CLARITY.
ALL RESISTORS ARE 1% OR BETTER.
ALL CAPACITORS ARE 5% OR BETTER.

28k

28k

R10

28k

R14

28k

R15

26.1k

R17

26.1k

R19

26.1k

R21

28k

R3

Ω

R7

Ω

Ω

Ω

Ω

Ω

Ω

Ω

C1

47nF

C3

47nF

C5

47nF

C7

47nF

28k

28k

R11

R4

Ω

Ω

C10
47nF

7.5k

7.5k

R18

R22

C2

47nF

R5

56.2k

Ω

C4

47nF

R8

56.2k

Ω

C6

47nF

R12

56.2k

Ω

C8

47nF

R16

13k

Ω

Ω

R20

13k

Ω

Ω

BIAS

BIAS

BIAS

BIAS

BIAS

BIAS

2

3

6

5

9

10

13

12

2

3

6

5

1

RIGHT
AUDIO
OUTPUT

7

RIGHT AND LEFT OUTPUTS
ARE AC-COUPLED TO A
MAX9709 CONFIGURED AS
A STEREO AMPLIFIER

LEFT
AUDIO
OUTPUT

SUBWOOFER OUTPUT IS
AC-COUPLED TO A
MAX9709 CONFIGURED AS
A MONO AMPLIFIER

SUBWOOFER
AUDIO
OUTPUT

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

______________________________________________________________________________________ 19

Pin Configurations

TOP VIEW

N.C.

OUTR-

OUTR-

OUTR+

OUTR+

PGND

PGND

OUTL-

OUTL-

OUTL+

OUTL+

N.C.

N.C.

DD

DD

PV

3637383940 3233343541

MAX9709

7654311109821312 141

DD

PV

DD

PV

TH0

DD

C1N

PV

PGND

PGND

PGND

PGND

PGND

DD

PV

N.C.

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

N.C.

PV

PGND

THIN QFN

TH1

C1P

TH2

DD

CPV

TEMP

SYNCOUT

MUTE

N.C.

SHDN

3031 29

SYNCIN

G2

FS2

28 G1N.C.

27

INR+

INR-

26

25

V

DD

24

SS

23

GND

GND

22

REG

21

REG

20

REG

19

MONO

18

INL+

17

INL-

16

15

FS1

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

20 ______________________________________________________________________________________

Chip Information

PROCESS: BiCMOS

Pin Configurations (continued)

TOP VIEW

N.C.

OUTL+

OUTL+

OUTL-

OUTL-

N.C.

PGND

PGND

N.C.

OUTR+

OUTR+

OUTR-

N.C.

N.C.

64

5859606162 5455565763

OUTR-

5253

N.C.

49

5051

48 N.C.N.C.

47

46

45

44

43

42

41

40

39

38

37

36

35

34

33

PGND

PGND

PGND

PV

PV

PV

N.C.

C1N

C1P

CPV

SYNCOUT

N.C.

SYNCIN

FS2

N.C.

1

2

3

4

5

DD

6

DD

7

DD

8

9

10

11

DD

12

13

14

15

16

MAX9709

PGND

PGND

PGND

PV

DD

PV

DD

PV

DD

N.C.

TH0

TH1

TH2

TEMP

MUTE

SHDN

G2

N.C.

2322212019 2726252418 2928 32313017

DD

N.C.

FS1

INL-

INL+

MONO

REG

REG

REG

GND

GND

SS

V

INR-

INR+

G1

N.C.

TQFP

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

______________________________________________________________________________________ 21

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages

.)

56L THIN QFN.EPS

PACKAGE OUTLINE
56L THIN QFN, 8x8x0.8mm

21-0135

1

E

2

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

22 ______________________________________________________________________________________

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages

.)

PACKAGE OUTLINE
56L THIN QFN, 8x8x0.8mm

21-0135

2

E

2

MAX9709

25W/50W, Filterless, Spread-Spectrum,

Stereo/Mono, Class D Amplifier

______________________________________________________________________________________ 23

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages

.)

64L TQFP.EPS

PACKAGE OUTLINE,
64L TQFP, 10x10x1.4mm

21-0083

1

B

2

MAX9709

25W/50W, Filterless, Spread-Spectrum,
Stereo/Mono, Class D Amplifier

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.

24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.

Quijano

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages

.)

Freed

PACKAGE OUTLINE,
64L TQFP, 10x10x1.4mm

21-0083

2

B

2