Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsLinear ICsLinear IC - Audio amplifier 2-channel (stereo) Class D TQFN 56 (8x8)

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-fre-

quency 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

TEMP RANGE PIN-PACKAGE

PKG

CODE

MAX9741ETN+

-40°C to +85°C

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

CLASS D

MODULATOR

OUTPUT

PROTECTION

MAX9741

Simplified Block Diagram

Summary of content (16 pages)

PAGE 1
9-3887; Rev 0; 2/06 KIT ATION EVALU E L B AVAILA 12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier Features 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.
PAGE 2
MAX9741 12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND.) VDD to PGND, AGND .............................................................30V OUTR_, OUTL_, C1N..................................-0.3V to (VDD + 0.3V) C1P............................................(VDD - 0.3V) to (CHOLD + 0.3V) CHOLD ........................................................(VDD - 0.3V) to +40V SHDN, FS_, G_ ....................................................
PAGE 3
12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier (VDD = 18V, GND = PGND = 0V, SHDN ≥ VIH, AV = 16dB, CSS = CIN = 0.47µF, CREG = 0.01µF, C1 = 100nF, C2 = 1µF, FS1 = FS2 = GND (fS = 670kHz), RL connected between OUTL+ and OUTL- and OUTR+ and OUTR-, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS Total Harmonic Distortion Plus Noise PCONT THD+N Signal-to-Noise Ratio SNR Crosstalk RL = 4Ω 6.
PAGE 4
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.) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 1 1 1 THD+N (%) VDD = 24V THD+N (%) VDD = 12V VDD = 24V VDD = 18V 0.1 0.1 0.01 0.
PAGE 5
12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier -80 LEFT TO RIGHT -60 -80 RIGHT TO LEFT -100 -100 -120 100 1k 10k 100k -60 -80 -100 -120 10 100 1k 10k 0 100k 2 4 6 8 10 12 14 16 18 20 FREQUENCY (Hz) FREQUENCY (Hz) FREQUENCY (kHz) OUTPUT FREQUENCY SPECTRUM OUTPUT FREQUENCY SPECTRUM WIDEBAND OUTPUT SPECTRUM (FFM MODE) -40 -60 -80 -100 -120 0 -20 -40 -60 -80 -100 -140 2 4 6 8 10 12 14 16 18 20 FREQUENCY (kHz) RBW = 10kHz -20 -40 -60 -80 -100 -120 -140 0 OUTPU
PAGE 6
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.) TURN-ON/TURN-OFF RESPONSE RBW = 10kHz -20 MAX9741 toc16 MAX9741 toc17 0 10 VDD = 12V SHDN 5V/div -40 RL = 8Ω CSS = 180pF VDD = 18V VDD = 24V 1 THD+N (%) OUTPUT AMPLITUDE (dBV) TOTAL HARMONIC DISTORTION PLUS NOISE vs.
PAGE 7
12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier PIN NAME FUNCTION 1, 4, 7, 11–15, 19, 21, 23, 25, 28, 33–36, 39, 42, 43, 44, 49, 50, 55, 56 N.C. 2, 3, 40, 41 PGND 5, 6, 37, 38 VDD Power-Supply Input 8 C1N Charge-Pump Flying Capacitor Negative Terminal 9 C1P Charge-Pump Flying Capacitor Positive Terminal 10 CHOLD 16 INL- Left-Channel Negative Input 17 INL+ Left-Channel Positive Input 18 SHDN Active-Low Shutdown. Connect SHDN to GND to disable the device.
PAGE 8
Operating Modes Fixed-Frequency Modulation (FFM) Mode The MAX9741 features three FFM modes with different switching frequencies (Table 1). In FFM 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). The MAX9741 allows the switching frequency to be changed by ±35%, should the frequency of one or more of the harmonics fall in a sensitive band.
PAGE 9
12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier to pure PWM Class D amplifiers. The outputs will contain both differential and common-mode noise at the switching frequency and its harmonics. In many applications, a simple ferrite bead filter (see the Simplified Block Diagram) will allow the amplifier to pass FCC EMI limits. Ferrite beads offer significant cost and size reductions when compared to conventional inductors.
PAGE 10
MAX9741 12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier Ferrite beads are available from many manufacturers. Table 3 lists some manufacturers who make ferrite beads and other products suitable for use with Class D amplifiers. Although they offer a low cost and small size, ferrite bead filters slightly increase distortion and slightly reduce efficiency.
PAGE 11
12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier 0.47µF SINGLE-ENDED AUDIO INPUT IN+ Component Selection Input Filter An input capacitor, CIN, in conjunction with the input impedance of the MAX9741, 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.
PAGE 12
MAX9741 12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier Audio content, both music and voice, has a much lower RMS value relative to its peak output power. Figure 5 shows a sine wave and an audio signal in the time domain. Both are measured for RMS value by the oscilloscope. Although the audio signal has a slightly higher peak value than the sine wave, its RMS value is almost half that of the sine wave.
PAGE 13
12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier 10V TO 25V 33µF 25V 2.2µF 25V* 2 3 PGND 0.47µF 0.47µF 2.2µF 25V* 5 6 37 38 VDD VDD 40 41 PGND 17 INL+ OUTL+ 54 MODULATOR 16 INL- OUTL+ 53 OUTL- 52 H-BRIDGE OUTL- 51 VREG VREG 0.47µF 31 FS1 32 FS2 OSCILLATOR 27 INR+ OUTR+ 48 MODULATOR 0.47µF 26 INR- OUTR+ 47 OUTR- 46 H-BRIDGE OUTR- 45 VIH VREG VREG 18 SHDN 29 G1 30 G2 20 SS 0.47µF VREG 0.01µF 10V 24 REG GAIN CONTROL SHUTDOWN CONTROL MAX9741 C1P 9 CHARGE PUMP 8 C1 0.
PAGE 14
12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier MAX9741 Pin Configuration G1 G2 FS1 FS2 N.C. N.C. N.C. N.C. VDD VDD N.C. PGND PGND N.C. TOP VIEW 42 41 40 39 38 37 36 35 34 33 32 31 30 29 N.C. 43 28 N.C. N.C. 44 27 INR+ OUTR- 45 26 INR- OUTR- 46 25 N.C. OUTR+ 47 24 REG OUTR+ 48 23 N.C. 22 AGND N.C. 49 MAX9741 N.C. 50 21 N.C. OUTL- 51 20 SS OUTL- 52 19 N.C. OUTL+ 53 18 SHDN OUTL+ 54 17 INL+ N.C. 55 16 INL- + 15 N.C. 10 11 12 13 14 N.C. VDD 9 N.C. N.
PAGE 15
12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier 56L THIN QFN.EPS PACKAGE OUTLINE 56L THIN QFN, 8x8x0.8mm 21-0135 E 1 2 ______________________________________________________________________________________ 15 MAX9741 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.
PAGE 16
MAX9741 12W+12W, Low-EMI, Spread-Spectrum, Stereo, Class D Amplifier 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 E 2 2 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.