MAXIM MAX9741 Technical data

General Description

The MAX9741 stereo Class D audio power amplifier
provides Class AB amplifier performance with Class D
efficiency, conserving board space and eliminating the
need for a bulky heatsink. Using a high-efficiency Class
D architecture, it delivers 12W continuous output power
into 8Ω loads. Proprietary modulation and switching
schemes render the traditional Class D EMI suppression
output filter unnecessary.

The MAX9741 offers two modulation schemes: a fixed-fre­quency mode (FFM), and a spread-spectrum mode (SSM)
that reduces EMI-radiated emissions. The device utilizes a
fully differential architecture, a full bridged output, and
offers comprehensive click-and-pop suppression.

The MAX9741 features high 80dB PSRR, low 0.1%
THD+N, and SNR in excess of 100dB. Short-circuit and
thermal-overload protection prevent the device from
being damaged during a fault condition. The MAX9741
is available in a 56-pin TQFN (8mm x 8mm x 0.8mm)
package. The MAX9741 is specified over the extended

-40°C to +85°C temperature range.

Applications

Features

♦ Low-EMI Class D Amplifier

♦ Spread-Spectrum Mode Reduces EMI

♦ Passes FCC EMI Limits with Ferrite Bead Filters

with 0.5m Cables

♦ 12W+12W Continuous Output Power into 8Ω

♦ Low 0.1% THD+N

♦ High PSRR (80dB at 1kHz)

♦ 10V to 25V Single-Supply Operation

♦ Differential Inputs Minimize Common-Mode Noise

♦ Pin-Selectable Gain Reduces Component Count

♦ Industry-Leading Click-and-Pop Suppression

♦ Short-Circuit and Thermal-Overload Protection

♦ Available in Thermally Efficient, Space-Saving

56-Pin TQFN (8mm x 8mm x 0.8mm) Package

MAX9741

12W+12W, Low-EMI, Spread-Spectrum,

Stereo, Class D Amplifier

________________________________________________________________ Maxim Integrated Products 1

19-3887; Rev 0; 2/06

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.

EVALUATION KIT

AVAILABLE

Ordering Information

PART

PKG

CODE

MAX9741ETN+

56 TQFN-EP*

T5688-3

+Denotes lead-free package.

*EP = Exposed paddle.

LCD/PDP TVs

CRT TVs

PC Speakers

Pin Configuration appears at end of data sheet.

CLASS D
AMPLIFIERS
DRIVE 2 X 12W
INTO 8Ω LOADS

GAIN

CONTROL

INR+

DIFFERENTIAL AUDIO

INPUTS ELIMINATE

NOISE PICKUP

PROGRAMMABLE

SWITCHING

FREQUENCY

INR-

INL+

INL-

FS1, FS2

G2

G1

2

CLASS D

MODULATOR

OUTPUT

PROTECTION

MAX9741

Simplified Block Diagram

TEMP RANGE PIN-PACKAGE

-40°C to +85°C

MAX9741

12W+12W, Low-EMI, Spread-Spectrum,
Stereo, Class D Amplifier

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

(All voltages referenced to GND.)
V

DD

to PGND, AGND .............................................................30V

OUTR_, OUTL_, C1N..................................-0.3V to (V

DD

+ 0.3V)

C1P............................................(V

DD

- 0.3V) to (CHOLD + 0.3V)

CHOLD........................................................(V

DD

- 0.3V) to +40V

SHDN, FS_, G_ ...........................................................-6.3V to 8V

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

Duration of OUTR_/OUTL_

Short Circuit to GND, V

DD

......................................Continuous

Continuous Input Current (V

DD

, PGND) ..................................2A

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

Thermal Limits (Note 1)

Continuous Power Dissipation (T

A

= +70°C)
Single-Layer PC Board

56-Pin TQFN (derate 28.6mW/°C above +70°C) ............2.29W

θ

JA

................................................................................ 35°C/W

θ

JC

............................................................................... 0.6°C/W

Continuous Power Dissipation (T

A

= +70°C)
Multiple-Layer PC Board

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

θ

JA

................................................................................ 21°C/W

θ

JC

............................................................................... 0.6°C/W

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

ELECTRICAL CHARACTERISTICS

(VDD= 18V, GND = PGND = 0V, SHDN ≥ VIH, AV= 16dB, CSS= CIN= 0.47µF, C

REG

= 0.01µF, C1 = 100nF, C2 = 1µF, FS1 = FS2 =

GND (f

S

= 670kHz), RLconnected between OUTL+ and OUTL- and OUTR+ and OUTR-, TA= T

MIN

to T

MAX

, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Notes 1, 2)

PARAMETER

CONDITIONS

GENERAL

Supply Voltage Range V

DD

Inferred from PSRR test 10 25 V

Quiescent Current I

DD

RL = Open 26 37

Shutdown Current

0.2 1.5 µA

CSS = 470nF 100

Turn-On Time t

ON

CSS = 180nF 50

Amplifier Output Resistance in
Shutdown

SHDN = GND 150 320 kΩ

AV = 13dB 35 53 80

AV = 16dB 30 45 65

AV = 19.1dB 23 36 55

Input Impedance R

IN

AV = 29.6dB 10

22

kΩ

G1 = L, G2 = L

G1 = L, G2 = H

G1 = H, G2 = L

13

Voltage Gain A

V

G1 = H, G2 = H

16

dB

Gain Matching Between channels 0.5 %

Output Offset Voltage V

OS

±5 ±30

Common-Mode Rejection Ratio

fIN = 1kHz, input referred 60 dB

VDD = 10V to 25V 48 83

f

RIPPLE

= 1kHz 80

Power-Supply Rejection Ratio
(Note 3)

PSRR

200mV

P-P

ripple

f

RIPPLE

= 20kHz 60

dB

Note 1: Thermal performance of this device is highly dependant on PC board layout. See the Applications Information for more

detail.

SYMBOL

MIN TYP MAX UNITS

I

SHDN

CMRR

14.3

29.4 29.6 29.8

18.9 19.1 19.3

12.8

15.9

mA

ms

13.2

16.3

mV

MAX9741

12W+12W, Low-EMI, Spread-Spectrum,

Stereo, Class D Amplifier

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VDD= 18V, GND = PGND = 0V, SHDN ≥ VIH, AV= 16dB, CSS= CIN= 0.47µF, C

REG

= 0.01µF, C1 = 100nF, C2 = 1µF, FS1 = FS2 =

GND (f

S

= 670kHz), RLconnected between OUTL+ and OUTL- and OUTR+ and OUTR-, TA= T

MIN

to T

MAX

, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Notes 1, 2)

PARAMETER

CONDITIONS

UNITS

RL = 8Ω 12

VDD = 18V, THD+N =
10%, f = 1kHz

R

L

= 4Ω 6.5

RL = 8Ω 11

VDD = 24V, THD+N =
10%, f = 1kHz

R

L

= 4Ω 5

RL = 8Ω 8

Continuous Output Power
(Notes 4, 5)

VDD = 12V, THD+N =
10%, f = 1kHz

R

L

= 4Ω 8.5

W

Total Harmonic Distortion Plus
Noise

fIN = 1kHz, either FFM or SSM, RL = 8Ω,
P

OUT

= 4W

0.1 %

FFM

SSM

FFM

Signal-to-Noise Ratio SNR

R

L

= 8Ω,

P

OUT

= 4W,

f = 1kHz

SSM

dB

Crosstalk Left to right, right to left, 8Ω load, fIN = 10kHz 65 dB

FS1 = L, FS2 = L 560 670 800

FS1 = L, FS2 = H 930

FS1 = H, FS2 = L 470

Oscillator Frequency f

OSC

FS1 = H, FS2 = H (spread-spectrum mode)

670

kHz

VDD = 12V, RL = 8Ω, P

OUT

= 8W 78

Efficiency (Note 4) η

V

DD

= 18V, RL = 8Ω, P

OUT

= 10W 78

%

Regulator Output V

REG

6V

DIGITAL INPUTS (SHDN, FS_, G_)

V

IH

2.5

Input Thresholds

V

IL

0.8

V

Input Leakage Current ±1µA

Note 2: All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design.
Note 3: PSRR is specified with the amplifier inputs connected to GND through C

IN

.

Note 4: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For R

L

= 8Ω, L = 68µH.

For R

L

= 12Ω, L = 100µH. For RL= 16Ω, L = 120µH.

Note 5: Output power measured at T

A

= +25°C, with a soak time of 15 minutes.

SYMBOL

P

THD+N

CONT

BW = 22Hz to 22kHz

Unweighted

A-weighted

MIN TYP MAX

95.8

91.8

99.1

95.7

±7%

MAX9741

12W+12W, Low-EMI, Spread-Spectrum,
Stereo, Class D Amplifier

4 _______________________________________________________________________________________

TOTAL HARMONIC DISTORTION PLUS

NOISE vs. OUTPUT POWER

MAX9741 toc01

OUTPUT POWER (W)

THD+N (%)

15105

0.1

1

10

0.01
020

RL = 8Ω

VDD = 24V

VDD = 18V

VDD = 12V

15

TOTAL HARMONIC DISTORTION PLUS

NOISE vs. OUTPUT POWER

MAX9741 toc02

OUTPUT POWER (W)

THD+N (%)

0.01

0.1

1

10

0

RL = 4Ω

VDD = 24V

VDD = 18V

VDD = 12V

105

TOTAL HARMONIC DISTORTION PLUS

NOISE vs. FREQUENCY

MAX9741 toc03

FREQUENCY (Hz)

THD+N (%)

10k1k100

0.1

1

10

0.01
10 100k

P

OUT

= 500mW

P

OUT

= 8W

TOTAL HARMONIC DISTORTION PLUS

NOISE vs. FREQUENCY

MAX974 toc04

FREQUENCY (Hz)

THD+N (%)

10k1k100

0.1

1

10

0.01
10 100k

P

OUT

= 8W

SSM

FFM

OUTPUT POWER vs. SUPPLY VOLTAGE

MAX9741 toc07

SUPPLY VOLTAGE (V)

OUTPUT POWER (W)

0

6

4

2

8

10

12

14

16

18

20

10 1613 19 22 25

RL = 8Ω

RL = 16Ω

TOTAL HARMONIC DISTORTION PLUS

NOISE vs. OUTPUT POWER

MAX9741 toc05

OUTPUT POWER (W)

THD+N (%)

15105

0.1

1

10

0.01

020

f = 100Hz

f = 10kHz

f = 1kHz

EFFICIENCY vs. OUTPUT POWER

MAX9741 toc06

OUTPUT POWER (W)

EFFICIENCY (%)

161248

10

20

30

40

50

60

70

80

90

100

0

0

RL = 8Ω

VDD = 18V

VDD = 12V

VDD = 24V

OUTPUT POWER vs. LOAD RESISTANCE

MAX9741 toc08

LOAD RESISTANCE (Ω)

OUTPUT POWER (W)

10

2

4

6

8

10

12

14

16

18

20

0

1 100

THD+N = 10%

THD+N = 1%

COMMON-MODE REJECTION RATIO

vs. FREQUENCY

MAX9741 toc09

FREQUENCY (Hz)

CMRR (dB)

10k1k100

-70

-60

-50

-40

-30

-20

-10

0

-80
10 100k

Typical Operating Characteristics

(VDD= 18V, RL= 8Ω, fIN= 1kHz, 33µH with 4Ω, 68µH with 8Ω, part in SSM mode, 136µH with 16Ω, measurement BW = 22Hz to
22kHz, unless otherwise noted.)

MAX9741

12W+12W, Low-EMI, Spread-Spectrum,

Stereo, Class D Amplifier

_______________________________________________________________________________________ 5

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

MAX9741 toc10

FREQUENCY (Hz)

PSRR (dB)

10k1k100

-100

-80

-60

-40

-20

0

-120
10 100k

200mV

P-P

INPUT

CROSSTALK vs. FREQUENCY

MAX9741 toc11

FREQUENCY (Hz)

CROSSTALK (dB)

10k1k100

-80

-100

-60

-40

-20

0

-120
10 100k

LEFT TO RIGHT

RIGHT TO LEFT

OUTPUT FREQUENCY SPECTRUM

MAX9741 toc12

FREQUENCY (kHz)

OUTPUT MAGNITUDE (dB)

-120

-100

-80

-60

-40

-20

0

20

-140
181612 144 6 8 102020

FFM MODE
UNWEIGHTED
f

IN

= 1kHz

P

OUT

= 5W

OUTPUT FREQUENCY SPECTRUM

MAX941 toc13

FREQUENCY (kHz)

OUTPUT MAGNITUDE (dB)

-120

-100

-80

-60

-40

-20

0

20

-140
181612 144 6 8 102020

SSM MODE
UNWEIGHTED
f

IN

= 1kHz

P

OUT

= 5W

OUTPUT FREQUENCY SPECTRUM

MAX9741 toc14

FREQUENCY (kHz)

OUTPUT MAGNITUDE (dB)

-120

-100

-80

-60

-40

-20

0

20

-140
181612 144 6 8 102020

SSM MODE
A-WEIGHTED
f

IN

= 1kHz

P

OUT

= 5W

100k 1M 10M 100M

WIDEBAND OUTPUT SPECTRUM

(FFM MODE)

MAX9741 toc15

FREQUENCY (Hz)

OUTPUT AMPLITUDE (dBV)

0

-120

-100

-80

-60

-40

-20

RBW = 10kHz

Typical Operating Characteristics (continued)

(VDD= 18V, RL= 8Ω, fIN= 1kHz, 33µH with 4Ω, 68µH with 8Ω, part in SSM mode, 136µH with 16Ω, measurement BW = 22Hz to
22kHz, unless otherwise noted.)