evaluation kit 3.2w, high-efficiency, low-emi, …max9759 3.2w, high-efficiency, low-emi,...

General DescriptionThe MAX9759 mono Class D, audio power amplifierprovides Class AB amplifier audio performance with thebenefits of Class D efficiency, eliminating the need for aheatsink and extending battery life. The MAX9759 deliv-ers up to 3.2W of continuous power into a 4Ω load whileoffering greater than 90% efficiency. Maxim’s next-gen-eration, low-EMI modulation scheme allows the amplifi-er to operate without an external LC filter while stillmeeting FCC EMI-radiated emission levels.

The MAX9759 offers two modulation schemes: a fixed-frequency modulation (FFM) mode and a spread-spec-trum modulation (SSM) mode. The SSM mode flattensthe wideband spectral components, reducing EMI-radi-ated emissions due to the modulation frequency.Furthermore, the MAX9759 oscillator can be synchro-nized to an external clock through the SYNC input,allowing the switching frequency to range from1000kHz to 1600kHz. The SYNC input and SYNC_OUToutput of the MAX9759 allow multiple Maxim Class Damplifiers to be cascaded and frequency locked, mini-mizing interference due to clock intermodulation. TheMAX9759 utilizes fully differential input amplifiers, a full-bridged output, comprehensive click-and-pop suppres-sion, and features four selectable gain settings (6dB,12dB, 18dB, 24dB).

The MAX9759 features high 81dB PSRR, low 0.02%THD+N, and SNR in excess of 90dB. Short-circuit andthermal-overload protection prevents damage to thedevice during a fault condition. The MAX9759 operatesfrom a single 5V supply, consumes 8.4mA of supplycurrent, and is available in a 16-pin thin QFN package(4mm x 4mm x 0.8mm). The MAX9759 is fully specifiedover the extended -40°C to +85°C temperature range.

ApplicationsCell Phones/PDAs

Notebook PCs

Portable DVD Players

Flat-Panel PC Monitors

LCD TVs

LCD Projectors

Features♦ 3.2W into 4Ω Load (THD+N = 10%)

♦ Filterless Amplifier Passes FCC RadiatedEmissions Standards with 7.6cm of Cable

♦ 92% Efficiency

♦ High PSRR (81dB at 1kHz)

♦ Low 0.02% THD+N

♦ External Clock Synchronization for Multiple,Cascaded Maxim Class D Amplifiers

♦ 3.0V to 5.5V Single-Supply Operation

♦ Pin-Selectable Gain (6dB, 12dB, 18dB, 24dB)

♦ Integrated Click-and-Pop Suppression

♦ Low Quiescent Current (8.4mA)

♦ Low-Power Shutdown Mode (10µA)

♦ Mute Function

♦ Short-Circuit and Thermal-Overload Protection

♦ Available in Thermally Efficient Package16-Pin TQFN (4mm x 4mm x 0.8mm)

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3.2W, High-Efficiency, Low-EMI,Filterless, Class D Audio Amplifier

________________________________________________________________ Maxim Integrated Products 1

MAX9759

DIFFERENTIALAUDIO INPUT

SYNCINPUT

SYNCOUTPUT

VDD

OSCILLATOR

MODULATORAND H-BRIDGE

MONO SPEAKEROUTPUT

GAINCONTROL

MUTECONTROL

SHDNCONTROL

G1G2

SHDN

MUTE

Simplified Block Diagram

Ordering Information

19-3691; Rev 1; 10/05

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.

EVALUATION KIT

AVAILABLE

PART TEMP RANGEPIN-PACKAGE

PKGCODE

MAX9759ETE+ -40°C to +85°C 16 TQFN-EP* T1644-4

Pin Configurations appear at end of data sheet.

+Denotes lead-free package.*EP = Exposed paddle.

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ABSOLUTE MAXIMUM RATINGS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functionaloperation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure toabsolute maximum rating conditions for extended periods may affect device reliability.

VDD to GND..............................................................................6VPVDD to PGND .........................................................................6VGND to PGND .......................................................-0.3V to +0.3VAll Other Pins to GND.................................-0.3V to (VDD + 0.3V)Continuous Current Into/Out of PVDD/PGND/OUT+/OUT-....1.7ADuration of OUT+ or OUT- Short Circuit to

VDD/GND/PVDD/PGND............................................ContinuousDuration of Short Circuit Between OUT+ and OUT- ..Continuous

Continuous Power Dissipation (TA = +70°C)16-Pin TQFN (derate 16.9mW/°C above +70°C) .....1349.1mW

Junction Temperature ......................................................+150°COperating Temperature Range ...........................-40°C to +85°CStorage Temperature Range .............................-65°C to +150°CLead Temperature (soldering, 10s) .................................+300°CESD Protection (+IBM).........................................................±2kV

ELECTRICAL CHARACTERISTICS (VDD = 5.0V)(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = 0V (FFM). Gain = 12dB (G1 = 0, G2 = 1). Speaker load resistor(RL) connected between OUT+ and OUT-, unless otherwise noted, RL = ∞, TA = TMIN to TMAX, unless otherwise noted. Typical val-ues are at TA = +25°C.) (Notes 1, 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

GENERAL

Supply Voltage Range VDD Inferred from PSRR test 3.0 5.5 V

Quiescent Current IDD No load 8.4 12 mA

Mute Current IMUTE V MUTE = 0V 5.5 8 mA

Shutdown Current IDD(SHDN) V SHDN = 0V 0.1 10 µA

Shutdown to Full Operation tSON 40 ms

Mute to Full Operation tMUTE 40 ms

Common-Mode Rejection Ratio CMRR f = 1kHz, input referred, VIN = 200mVP-P 67 dB

Input DC Bias Voltage VCM 1.3 1.5 1.7 V

Gain = +24dB 14 20 26

Gain = +18dB 25 36 47

Gain = +12dB 40 60 80Input Resistance RIN

Gain = +6dB 60 90 120

kΩ

G1 = 0, G2 = 0 +22 +24 +26

G1 = 1, G2 = 0 +16 +18 +20

G1 = 0, G2 = 1 +10 +12 +14Voltage Gain AV

G1 = 1, G2 = 1 +4 +6 +8

dB

Output Offset Voltage VOS TA = +25°C ±10 ±50 mV

VDD = 4.5V to 5.5V 62 90

fRIPPLE = 217Hz 79

fRIPPLE = 1kHz 81Power-Supply Rejection Ratio(Note 3)

PSRR200mVP-P ripple

fRIPPLE = 20kHz 70

dB

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3.2W, High Efficiency, Low-EMI, Filterless,Class D Audio Amplifier

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (VDD = 5.0V) (continued)(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = 0V (FFM). Gain = 12dB (G1 = 0, G2 = 1). Speaker load resistor(RL) connected between OUT+ and OUT-, unless otherwise noted, RL = ∞, TA = TMIN to TMAX, unless otherwise noted. Typical val-ues are at TA = +25°C.) (Notes 1, 2)


RL = 3Ω 3.4

RL = 4Ω 2.6THD+N = 1%

RL = 8Ω 1.4

RL = 3Ω 4.3

RL = 4Ω 3.2

Output Power POUT

THD+N = 10%

RL = 8Ω 1.8

W

RL = 3Ω 0.08

RL = 4Ω 0.05Total Harmonic Distortion PlusNoise

THD+NfIN = 1kHz, eitherFFM or SSM,POUT = 1W RL = 8Ω 0.02

%

FFM 93BW = 22Hz to22kHz SSM 89

FFM 96Signal-to-Noise Ratio SNR

POUT = 1W,RL = 8Ω

A-weightedSSM 92

dB

SYNC = GND (FFM mode) 1000 1100 1200

SYNC = FLOAT (FFM mode) 1102 1500 1837Oscillator Frequency fOSC

SYNC = VDD (SSM mode)1200±70

kHz

SYNC Frequency Lock Range TTL-compatible clock input 1000 1600 kHz

Into shutdown -50Click-and-Pop Level KCP

Peak voltage,A-weighted, 32 samplesper second (Notes 3, 4) Out of shutdown -57

dBV

Efficiency η POUT = 1W, fIN = 1kHz, RL = 8Ω in serieswith 68µH

92 %

DIGITAL INPUTS (SHDN, MUTE, G1, G2, SYNC)

SYNC, G1, G2 Input Voltage High VINH VDD x 0.9 V

SYNC, G1, G2 Input Voltage Low VINL VDD x 0.1 V

SHDN, MUTE Voltage High VINH 2 V

SHDN, MUTE Voltage Low VINL 0.8 V

SYNC Input Resistance 200 kΩSYNC Input Current ±35 µASHDN, MUTE, G1, G2 InputCurrent

±1 µA

SYNC Capacitance 10 pF

DIGITAL OUTPUTS (SYNC_OUT)

Output Voltage High VOH IOH = 3mA 2.4 V

Output Voltage Low VOL IOL = 3mA 0.4 V

SYNC_OUT Capacitive Drive TTL-compatible clock output 100 pF

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ELECTRICAL CHARACTERISTICS (VDD = 3.3V)(VDD = PVDD = SHDN = MUTE = 3.3V, GND = PGND = 0V, SYNC = GND (FFM). Gain = 12dB (G1 = 0, G2 = 1). Speaker load resis-tor (RL) connected between OUT+ and OUT-, unless otherwise noted. RL = ∞, TA = TMIN to TMAX, unless otherwise noted. Typicalvalues are at TA = +25°C.) (Notes 1, 2)


Quiescent Current IDD 6 mA

Mute Current IMUTE V MUTE = 0V 5 A

Shutdown Current ISHDN V SHDN = 0V 0.1 µA

Common-Mode Rejection Ratio CMRR f = 1kHz, input referred 67 dB

VDD = 3.0V to 5.5V 50 72 dBfRIPPLE = 217Hz 79

fRIPPLE = 1kHz 81Power-Supply Rejection Ratio PSRR

200mVP-P ripple

fRIPPLE = 20kHz 70

dB

RL = 3Ω 1.5

RL = 4Ω 1.1THD+N = 1%

RL = 8Ω 0.65

RL = 3Ω 1.8

RL = 4Ω 1.3

Output Power POUT

THD+N = 10%

RL = 8Ω 0.78

W

RL = 3Ω 0.06

RL = 4Ω 0.04Total Harmonic Distortion PlusNoise

THD+Nf = 1kHz, eitherFFM or SSM,POUT = 500mW RL = 8Ω 0.02

%

FFM 93BW = 22Hzto 22kHz SSM 89

FFM 96Signal-to-Noise Ratio SNR

POUT = 500mW,RL = 8Ω

A-weightedSSM 92

dB

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 RL = 4Ω, L = 33µH.

For RL = 8Ω, L = 68µH.Note 3: Inputs AC-coupled to GND.Note 4: Testing performed with 8Ω resistive load in series with a 68µH inductive load across BTL outputs. Mode transitions are con-

trolled by the SHDN pin.

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Typical Operating Characteristics(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = VDD (SSM), unless otherwise noted. Gain = 12dB (G1 = 0, G2 = 1).THD+N measurement bandwidth: 22Hz to 22kHz. Typical values are at TA = +25°C.) (See Typical Operating Circuit)

TOTAL HARMONIC DISTORTION PLUS NOISEvs. FREQUENCY

MAX

9759

toc0

1

FREQUENCY (Hz)

THD+

N (%

)

10k1k100

0.01

0.1

1

10

0.00110 100k

VDD = 5VRL = 3Ω

POUT = 1W

POUT = 2.6W


MAX

9759

toc0

2

FREQUENCY (Hz)

THD+

N (%

)

10k1k100

0.01

0.1

1

10

0.00110 100k

VDD = 3.3VRL = 3Ω

POUT = 500mW

POUT = 1.3W


MAX

9759

toc0

3

FREQUENCY (Hz)

THD+

N (%

)

10k1k100

0.01

0.1

1

10

0.00110 100k

VDD = 5VRL = 4Ω

POUT = 1W

POUT = 2.2W


MAX

9759

toc0

4

FREQUENCY (Hz)

THD+

N (%

)

10k1k100

0.01

0.1

1

10

0.00110 100k

VDD = 3.3VRL = 4Ω

POUT = 500mW

POUT = 700mW


MAX

9759

toc0

5

FREQUENCY (Hz)

THD+

N (%

)

10k1k100

0.01

0.1

1

10

0.00110 100k

VDD = 5VRL = 8Ω

POUT = 600mW

POUT = 1.2W


MAX

9759

toc0

6

FREQUENCY (Hz)

THD+

N (%

)

10k1k100

0.01

0.001

0.1

1

10

10 100k

VDD = 3.3VRL = 8Ω

POUT = 300mW

POUT = 500mW


MAX

9759

toc0

7

FREQUENCY (Hz)

THD+

N (%

)

10k1k100

0.01

0.1

1

10

0.00110 100k

VDD = 5VRL = 8ΩPOUT = 1.2W

SSM

FFM

TOTAL HARMONIC DISTORTION PLUS NOISEvs. OUTPUT POWER

MAX

9759

toc0

8

OUTPUT POWER (W)

THD+

N (%

)

4321

0.01

0.1

1

10

100

0.0010

VDD = 5VRL = 3Ω

fIN = 200Hz, 1kHz

fIN = 10kHz


MAX

9759

toc0

9

OUTPUT POWER (W)

THD+

N (%

)

1.51.00.5

0.01

0.1

1

10

100

0.0010 2.0

VDD = 3.3VRL = 3Ω

fIN = 200Hz, 1kHz

fIN = 10kHz

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MAX

9759

toc1

2

OUTPUT POWER (W)

THD+

N (%

)

1.51.00.5

0.01

0.1

1

10

100

0.0010 2.0

VDD = 5VRL = 8Ω

fIN = 200Hz, 1kHz

fIN = 10kHz


MAX

9759

toc1

3

OUTPUT POWER (W)

THD+

N (%

)

0.60.40.2

0.01

0.1

1

10

100

0.0010 0.8

VDD = 3.3VRL = 8Ω

fIN = 200Hz, 1kHz

fIN = 10kHz


MAX

9759

toc1

4

OUTPUT POWER (W)

THD+

N (%

)

1.51.00.5

0.01

0.1

1

10

100

0.0010 2.0

VDD = 5VfIN = 1kHzRL = 8Ω

f = 1180kHz, FFM

f = 1400kHz, FFM

EFFICIENCY vs. OUTPUT POWER

MAX

9759

toc1

5

OUTPUT POWER (W)

EFFI

CIEN

CY (%

)

4321

10

20

30

40

50

60

70

80

90

100

00 5

RL = 8Ω RL = 4ΩRL = 3Ω

VDD = 5VfIN = 1kHz


MAX

9759

toc1

6

OUTPUT POWER (W)

EFFI

CIEN

CY (%

)

1.51.00.5

10

20

30

40

50

60

70

80

90

100

00 2.0

RL = 8Ω RL = 4Ω RL = 3Ω

VDD = 3.3VfIN = 1kHz

EFFICIENCY vs. SUPPLY VOLTAGE

MAX

9759

toc1

7

SUPPLY VOLTAGE (V)

EFFI

CIEN

CY (%

)

5.55.04.54.03.5

40

50

60

70

80

90

100

303.0

RL = 8ΩRL = 4Ω

fIN = 1kHzTHD+N = 1%

OUTPUT POWERvs. SUPPLY VOLTAGE

MAX

9759

toc1

8

SUPPLY VOLTAGE (V)

OUTP

UT P

OWER

(W)

5.55.04.54.03.5

1

2

3

4

5

6

03.0

RL = 3ΩfIN = 1kHz

THD+N = 1%

THD+N = 10%

Typical Operating Characteristics (continued)(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = VDD (SSM), unless otherwise noted. Gain = 12dB (G1 = 0, G2 = 1).THD+N measurement bandwidth: 22Hz to 22kHz. Typical values are at TA = +25°C.) (See Typical Operating Circuit)


MAX

9759

toc1

0

OUTPUT POWER (W)

THD+

N (%

)

321

0.01

0.1

1

10

100

0.0010

VDD = 5VRL = 4Ω

fIN = 200Hz, 1kHz

fIN = 10kHz


MAX

9759

toc1

1

OUTPUT POWER (W)

THD+

N (%

)

1.00.5

0.01

0.1

1

10

100

0.0010 1.5

VDD = 3.3VRL = 4Ω

fIN = 200Hz, 1kHz

fIN = 10kHz

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TOTAL HARMONIC DISTORTION PLUS NOISEvs. COMMON-MODE VOLTAGE

MAX

9759

toc2

4

COMMON-MODE VOLTAGE (V)

THD+

N (%

)

321

0.01

0.1

1

10

100

0.0010 4

VDD = 5VRL = 8ΩfIN = 1kHzPOUT = 300mWDIFF INPUT


VDD = 3.3VRL = 8ΩfIN = 1kHzPOUT = 300mWDIFF INPUT


OUTPUT POWER vs. SUPPLY VOLTAGE

MAX

9759

toc1

9

SUPPLY VOLTAGE (V)

OUTP

UT P

OWER

(W)

5.55.03.5 4.0 4.5

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

03.0

RL = 4ΩfIN = 1kHz

THD+N = 10%

THD+N = 1%

OUTPUT POWER vs. SUPPLY VOLTAGE

MAX

9759

toc2

0

SUPPLY VOLTAGE (V)OU

TPUT

POW

ER (W

)

5.55.04.54.03.5

0.5

1.0

1.5

2.0

2.5

03.0

RL = 8ΩfIN = 1kHz

THD+N = 10%

THD+N = 1%

OUTPUT POWER vs. LOAD RESISTANCE

MAX

9759

toc2

1

LOAD RESISTANCE (Ω)

OUTP

UT P

OWER

(W)

10

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

01 100

VDD = 5VfIN = 1kHz

10% THD+N

1% THD+N

OUTPUT POWER vs. LOAD RESISTANCE

MAX

9759

toc2

2

LOAD RESISTANCE (Ω)

OUTP

UT P

OWER

(W)

10

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

01 100

VDD = 3.3VfIN = 1kHz

10% THD+N

1% THD+N

TOTAL HARMONIC DISTORTION PLUS NOISEvs. COMMON-MODE VOLTAGE

MAX

9759

toc2

3

COMMON-MODE VOLTAGE (V)

THD+

N (%

)

321

0.01

0.1

1

10

100

0.0010 4


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COMMON-MODE REJECTION RATIOvs. FREQUENCY

MAX

9759

toc2

5

FREQUENCY (Hz)

CMRR

(dB)

10k1k100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

-10010 100k

INPUT REFERRED VIN = 200mVP-P

POWER-SUPPLY REJECTION RATIOvs. FREQUENCY

MAX

9759

toc2

6

FREQUENCY (Hz)

PSRR

(dB)

10k1k100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

-10010 100k

OUTPUT REFERRED INPUTS AC GROUNDED


MUTE RESPONSEMAX9759 toc32

20ms/div

5V

0V

500mV/divMAX9759OUTPUT

MUTE

f = 1kHzRL = 8Ω

SHUTDOWN RESPONSEMAX9759 toc31

20ms/div

5V

0V

500mV/divMAX9759OUTPUT

SHDN

f = 1kHzRL = 8Ω

OUTPUT FREQUENCY SPECTRUM

MAX

9759

toc2

8

FREQUENCY (Hz)

OUTP

UT M

AGNI

TUDE

(dBV

)

15k10k5k

-120

-100

-80

-60

-40

-20

0

-1400 20k

SSM MODE VOUT = -60dBVfIN = 1kHzRL = 8ΩUNWEIGHTED

WIDEBAND OUTPUT SPECTRUM (FFM MODE)

MAX

9759

toc2

9

FREQUENCY (Hz)

OUTP

UT A

MPL

ITUD

E (d

BV)

100M10M

-50

-40

-30

-20

-10

0

10

20

30

40

-601M 1000M

RBW = 10kHz

OUTPUT FREQUENCY SPECTRUM

MAX

9759

toc2

7

FREQUENCY (Hz)

OUTP

UT M

AGNI

TUDE

(dBV

)

15k10k5k

-120

-100

-80

-60

-40

-20

0

-1400 20k

FFM MODE VOUT = -60dBVfIN = 1kHzRL = 8ΩUNWEIGHTED

WIDEBAND OUTPUT SPECTRUM (SSM MODE)

MAX

9759

toc3

0

FREQUENCY (Hz)

OUTP

UT A

MPL

ITUD

E (d

BV)

100M10M

-50

-40

-30

-20

-10

0

10

20

30

40

-601M 1000M

RBW = 10kHz

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MAX9759

2

16

3

15

7

6, 14 4

1µF

PGND

OUT+

OUT-

PVDD

PVDD

GND

IN+

VDD

VDD

18

IN-

SYNC

UVLO/POWERMANAGEMENT

CLASS DMODULATOR

PVDD

9, 12

11

10

CLICK-AND-POPSUPPRESSION

OSCILLATOR

10µF*

1µF

1µF

MUTE

5

SHDN

CONTROLVDD

GND

RIN

RIN

G1

G2

BIAS

NOTE: TYPICAL OPERATING CIRCUIT DEPICTS MAX9759 IN FFM MODE WITH fS = 1400kHz and +18dB OF GAIN.

*BULK CAPACITANCE, IF NEEDED.

SYNC_OUT 13

RF

RF

Typical Operating Circuit/Functional Diagram


SUPPLY CURRENTvs. SUPPLY VOLTAGE

MAX

9759

toc3

3

SUPPLY VOLTAGE (V)

SUPP

LY C

URRE

NT (m

A)

5.55.04.54.03.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

4.53.0

FFMTA = +85°C

TA = -40°C

TA = +25°C

SHUTDOWN SUPPLY CURRENTvs. SUPPLY VOLTAGE

MAX

9759

toc3

4

SUPPLY VOLTAGE (V)

SUPP

LY C

URRE

NT (µ

A)

5.35.14.94.7

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

04.5 5.5

TA = +85°C

TA = +25°C

TA = -40°C

FFM

PACKAGE TEMPERATUREvs. TIME

MAX

9759

toc3

5

TIME (s)

PACK

AGE

TEM

PERA

TURE

(°C)

25020015010050

10

20

30

40

50

60

00 300

RL = 8Ω AT 10% THD+N



MAX9759EVKITFREE AIRTA = +25°CfIN = 1kHz SINE WAVE

Detailed DescriptionOperating Modes

The MAX9759 filterless, Class D audio power amplifierfeatures several improvements to switch-mode amplifiertechnology. The MAX9759 offers Class AB performancewith Class D efficiency, while occupying minimal boardspace. A unique modulation scheme, synchronizableswitching frequency, and SSM mode create a compact,flexible, low-noise, efficient audio power amplifier. Thedifferential input architecture reduces common-modenoise pickup, and can be used without input-couplingcapacitors. The device can also be configured as a sin-gle-ended input amplifier.

Comparators monitor the MAX9759 inputs and com-pare the complementary input voltages to the sawtoothwaveform. The comparators trip when the input magni-tude of the sawtooth exceeds their corresponding inputvoltage. Both comparators reset at a fixed time after therising edge of the second comparator trip point, gener-

ating a minimum-width pulse tON(MIN) at the output ofthe second comparator (Figure 1). As the input voltageincreases or decreases, the duration of the pulse atone output increases (the first comparator to trip) whilethe other output pulse duration remains at tON(MIN).This causes the net voltage across the speaker (VOUT+- VOUT-) to change.

Fixed-Frequency Modulation (FFM) ModeThe MAX9759 features two FFM modes. The FFMmodes are selected by setting SYNC = GND for a1.1MHz switching frequency, and SYNC = FLOAT for a1.5MHz switching frequency. In FFM mode, the fre-quency spectrum of the Class D output consists of thefundamental switching frequency and its associatedharmonics (see the Wideband Output Spectrum (FFMMode) graph in the Typical Operating Characteristics).The MAX9759 allows the switching frequency to bechanged, should the frequency of one or more of theharmonics fall in a sensitive band. This can be done atany time and does not affect audio reproduction.

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Pin Description

PIN NAME FUNCTION

1 VDD Analog Power Supply. Bypass to GND with a 1µF ceramic capacitor.

2 IN+ Noninverting Audio Input

3 IN- Inverting Audio Input

4 GND Analog Ground

5 SHDNActive-Low Shutdown Input. Drive SHDN low to shut down the MAX9759. Connect to VDD for normaloperation.

6, 14 PGND Power Ground

7 SYNC

Frequency Select and External Clock Input:SYNC = GND: Fixed-frequency mode with fS = 1100kHz.SYNC = FLOAT: Fixed-frequency mode with fS = 1500kHz.SYNC = VDD: Spread-spectrum mode with fS = 1200kHz ±70kHz.SYNC = Clocked: Fixed-frequency mode with fS = external clock frequency.

8 MUTEActive-Low Mute Function. Drive MUTE low to disable the H-bridge outputs. Connect to VDD fornormal operation.

9, 12 PVDD H-Bridge Power Supply. Bypass to PGND with a 10µF ceramic capacitor.

10 OUT- Negative Speaker Output

11 OUT+ Positive Speaker Output

13 SYNC_OUTInternal Clock Output. Connect SYNC_OUT to the clock input of cascaded Maxim Class Damplifiers. Float SYNC_OUT if unused.

15 G2 Gain Control 2 (See Table 2)

16 G1 Gain Control 1 (See Table 2)

EP EPExposed Paddle. Can be left floating or tied to GND. For optimum thermal performance, connect EPto GND.

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Spread-Spectrum Modulation (SSM) ModeThe MAX9759 features a unique spread-spectrum modethat reduces peak component energy in the widebandspectrum, improving EMI emissions that may be radiat-ed by the speaker and cables by 5dB. Proprietary tech-

niques ensure that the cycle-to-cycle variation of theswitching period does not degrade audio reproductionor efficiency (see the Typical Operating Characteristics).Select SSM mode by setting SYNC = VDD. In SSMmode, the switching frequency varies by ±70kHz aroundthe center frequency (1.2MHz). The modulation schemeremains the same, but the period of the sawtooth wave-form changes from cycle to cycle (Figure 2). Instead of alarge amount of spectral energy present at multiples ofthe switching frequency, the energy is now spread overa bandwidth that increases with frequency. Above a fewmegahertz, the wideband spectrum looks like whitenoise for EMI purposes (Figure 3).

OUT+

OUT-

VIN-

VIN+

VOUT+ - VOUT-

tON(MIN)

tSW

Figure 1. MAX9759 Outputs with an Input Signal Applied

SYNC INPUT MODE

GND FFM with fS = 1100kHz

FLOAT FFM with fS = 1500kHz

VDD SSM with fS = 1200kHz ±70kHz

Clocked FFM with fS = external clock frequency

Table 1. Operating Modes

External SynchronizationThe SYNC function allows the MAX9759 to allocatespectral components of the switching harmonics toinsensitive frequency bands and facilitates synchroniza-tion to a system clock (allowing for a fully synchronoussystem). Applying an external TTL clock of 1000kHz to1600kHz to SYNC synchronizes the switching frequencyof the MAX9759. The period of the SYNC clock can berandomized, enabling the MAX9759 to be synchronizedto another MAX9759 operating in SSM mode.

Cascading AmplifiersThe SYNC_OUT function of the MAX9759 allows formultiple Maxim Class D amplifiers to be cascaded andfrequency locked. Synchronizing multiple Class Damplifiers ensures that no beat frequencies within the

audio spectrum occur on the power-supply rails. Anyintermodulation distortion due to the interference ofseveral modulation frequencies is minimized as aresult. Leave the SYNC_OUT pin of the MAX9759 float-ing if the SYNC_OUT function is not applicable.

Filterless Modulation/Common-Mode IdleThe MAX9759 uses Maxim’s unique modulationscheme that eliminates the LC filter required by tradi-tional Class D amplifiers, improving efficiency, reduc-ing component count, and conserving board spaceand system cost. Conventional Class D amplifiers out-put a 50% duty-cycle square wave when no signal ispresent. With no filter, the square wave appears acrossthe load as a DC voltage, resulting in finite load current,increasing power consumption. When no signal is pre-

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VOUT+ - VOUT-

tSW tSW tSW tSW

VIN-

VIN+

OUT+

OUT-

tON(MIN)

Figure 2. MAX9759 Outputs with an Input Signal Applied (SSM Mode)

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sent at the input of the MAX9759, the outputs switch asshown in Figure 4. Because the MAX9759 drives thespeaker differentially, the two outputs cancel each other,resulting in no net Idle Mode™ voltage across thespeaker and minimal power consumption.

EfficiencyEfficiency of a Class D amplifier is mostly associatedwith the region of operation of the output stage transis-tors. In a Class D amplifier, the output transistors act ascurrent-steering switches and consume negligible addi-tional power. Any power loss associated with the ClassD output stage is mostly due to the I x R loss of theMOSFET on-resistance and quiescent current overhead.

The theoretical best efficiency of a linear amplifier is78%; however, that efficiency is only exhibited at peakoutput powers. Under normal operating levels (i.e., typi-cal music reproduction levels), efficiency of a linearamplifier can fall below 30%. The MAX9759 Class Damplifier still exhibits >90% efficiencies under the sameconditions (Figure 5).

Gain SelectionThe MAX9759 features an internally set, logic-selec-table gain. The G1 and G2 logic inputs set the gain ofthe MAX9759 speaker amplifier (Table 2).

ShutdownThe MAX9759 features a shutdown mode that reducespower consumption and extends battery life. DrivingSHDN low places the MAX9759 in a low-power (0.1µA)shutdown mode. Drive SHDN high for normal operation.

30 60 80 100 120 140 160 180 280 300220200 240 26015

20

25

30

35

40

45

50

AMPL

ITUD

E (d

BµV/

m)

FREQUENCY (MHz)

MAX9759OUTPUT SPECTRUM

FCC LIMIT

Figure 3. MAX9759 EMI Spectrum

VIN = 0V

OUT-

OUT+

VOUT+ - VOUT- = 0V

Figure 4. MAX9759 Outputs with No Input Signal

0

30

20

10

50

40

90

80

70

60

100

0 0.2 0.4 0.8 1.20.6 1.0


OUTPUT POWER (W)

EFFI

CIEN

CY (%

)

VDD = 5Vf = 1kHzRL = 8Ω

CLASS AB

MAX9759

Figure 5. MAX9759 Efficiency vs. Output Power

G2 G1 GAIN (dB)

0 0 +24

0 1 +18

1 0 +12

1 1 +6

Table 2. Gain Selection

Idle Mode is a trademark of Maxim Integrated Products, Inc.

MuteThe MAX9759 features a mute function that disablesthe H-bridge outputs of the switching amplifier. Themute function only affects the power amplifiers of theMAX9759; it does not shut down the device. DrivingMUTE low places the MAX9759 in a disabled outputmode. Drive MUTE high for normal operation.

Click-and-Pop SuppressionThe MAX9759 features comprehensive click-and-popsuppression that eliminates audible transients on startupand shutdown. While in shutdown, the H-bridge is in ahigh-impedance state. During startup or power-up, theinput amplifiers are muted and an internal loop sets themodulator bias voltages to the correct levels, preventingclicks and pops when the H-bridge is subsequentlyenabled. For 40ms following startup, a soft-start functiongradually unmutes the input amplifiers.

For improved click-and-pop performance, sequence thedigital inputs of the SHDN and MUTE pins of theMAX9759 during power-up and power-down of thedevice such that transients are eliminated from eachpower cycle. Apply power to the MAX9759 with bothSHDN and MUTE held low. Release SHDN before MUTEsuch that minimal transients occur during startup of thedevice. The mute function allows the MAX9759 to bepowered up with the H-bridge outputs of the switchingamplifier disabled. For power-down, sequence the powercycle such that the amplifier is muted first and subse-quently shut down before power is disconnected from theIC. This power cycle eliminates any audible transients onpower-up and power-down of the MAX9759.

Applications InformationFilterless Operation

Traditional Class D amplifiers require an output filter torecover the audio signal from the amplifier’s output. Thefilters add cost, increase the solution size of the amplifi-er, and can decrease efficiency. The traditional PWMscheme uses large differential output swings (2 x VDDpeak-to-peak) and causes large ripple currents. Anyparasitic resistance in the filter components results in aloss of power, lowering the efficiency.

The MAX9759 does not require an output filter for the shortspeaker cable. The device relies on the inherent induc-tance of the speaker coil and the natural filtering of boththe speaker and the human ear to recover the audio com-ponent of the square-wave output. Eliminating the outputfilter results in a smaller, less costly, more efficient solution.

Because the frequency of the MAX9759 output is wellbeyond the bandwidth of most speakers, voice coilmovement due to the switching frequency is very small.

Although this movement is small, a speaker notdesigned to handle the additional power can be dam-aged. For optimum results, use a speaker with a seriesinductance > 10µH to 100µH range.

Power-Conversion EfficiencyUnlike a Class AB amplifier, the output offset voltage of aClass D amplifier does not noticeably increase quiescentcurrent draw when a load is applied. This is due to thepower conversion of the Class D amplifier. For example,an 8mV DC offset across an 8Ω load results in 1mA extracurrent consumption in a Class AB device. In the ClassD case, an 8mV offset into an 8Ω load equates to anadditional power drain of 8µW. Due to the high efficiencyof the Class D amplifier, this represents an additionalquiescent current draw of 8µW/(VDD/100η), which is onthe order of a few microamps.

Input AmplifierDifferential Input

The MAX9759 features a differential input structure,making it compatible with many CODECs, and offersimproved noise immunity over a single-ended inputamplifier. High-frequency signals can be picked up bythe amplifier’s input traces and can appear at theamplifier’s inputs as common-mode noise. A differentialinput amplifier amplifies the difference of the twoinputs; any signal common to both inputs is cancelled.

Single-Ended InputThe MAX9759 can be configured as a single-ended inputamplifier by capacitively coupling one input to GND whilesimultaneously driving the other input (Figure 6).

DC-Coupled InputThe input amplifier can accept DC-coupled inputs thatare biased within the amplifier’s common-mode range(see the Typical Operating Characteristics). DC couplingeliminates the input-coupling capacitors, reducing com-ponent count to potentially one external component (seethe System Diagram). However, the low-frequency rejec-tion of the capacitors is lost, allowing low-frequency sig-nals to feedthrough to the load.

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1µF

IN+

IN-

1µF

SINGLE-ENDEDAUDIO INPUT

MAX9759

Figure 6. Single-Ended Input

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______________________________________________________________________________________ 15

Component SelectionInput Filter

An input capacitor, CIN, in conjunction with the inputimpedance of the MAX9759 forms a highpass filter thatremoves the DC bias from an incoming signal. The AC-coupling capacitor allows the amplifier to bias the sig-nal to an optimum DC level. Assuming zero sourceimpedance, the -3dB point of the highpass filter isgiven by:

f-3dB = 1/(2πRINCIN)

Choose CIN such that f-3dB is well below the lowest fre-quency of interest. Setting f-3dB too high affects thelow-frequency response of the amplifier. Use capaci-tors whose dielectrics have low-voltage coefficients,such as tantalum or aluminum electrolytic. Capacitorswith high-voltage coefficients, such as ceramics, mayresult in increased distortion at low frequencies.

IN+

IN-

OUT+

OUT-

SYNC_OUT

RIGHT-CHANNELDIFFERENTIALAUDIO INPUT

MAX9759

VDD

VDD PVDD

IN+

IN-

OUT+

SYNC_OUT

SYNC

LEFT-CHANNELDIFFERENTIALAUDIO INPUT

MAX9759

VDD PVDD

IN+

IN-

OUT+

SYNC_OUT

SYNC

DIFFERENTIALAUDIO INPUT

MAX9759

VDD PVDD

SYNC

U1

U2

Figure 7. Master-Slave Configuration

100

0 0.5 1.0 1.5 2.0

10

1

0.1

0.01

0.001


OUTPUT POWER (W)

THD+

N (%

)

VDD = 5.0Vf = 1kHzRL = 8ΩSLAVE DEVICE

Figure 8. Total Harmonic Distortion Plus Noise vs. OutputVoltage

-15010 100 1k 100k

CROSSTALK vs. FREQUENCY

-130

-110

-90

-30

FREQUENCY (Hz)

CROS

STAL

K (d

B)

-70

-50

10k

VDD = 5VRL = 8Ωf = 1kHz

MASTER TO SLAVE

SLAVE TO MASTER

Figure 9. Crosstalk vs. Frequency

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Output FilterThe MAX9759 does not require an output filter for theshort speaker cable. The device passes FCC emissionsstandards with 7.6cm of unshielded speaker cables.However, output filtering can be used if a design is fail-ing radiated emissions due to board layout, cablelength, or the circuit’s close proximity to EMI-sensitivedevices. Use an LC filter when radiated emissions are aconcern, or when long leads are used to connect theamplifier to the speaker.

Supply Bypassing, Layout, and GroundingProper power-supply bypassing ensures low-distortionoperation. For optimum performance, bypass VDD toGND and PVDD to PGND with separate 0.1µF capaci-tors as close to each pin as possible. A low-imped-ance, high-current, power-supply connection to PVDDis assumed. Additional bulk capacitance should beadded as required depending on the application andpower-supply characteristics. GND and PGND shouldbe star-connected to system ground.

Use wide, low-resistance output traces. As load imped-ance decreases, the current drawn from the device out-puts increase. At higher current, the resistance of theoutput traces decrease the power delivered to the load.Wide output, supply, and GND traces also improve thepower dissipation of the device.

The MAX9759 thin QFN package features an exposedthermal pad on its underside. This pad lowers thepackage’s thermal resistance by providing a directheat conduction path. Due to the high efficiency of theMAX9759’s Class D Amplifier, an external heatsink isnot required. For optimum thermal performance, con-nect the exposed paddle to GND.

Stereo ConfigurationTwo MAX9759s can be configured as a stereo amplifier(Figure 7). Device U1 is the master amplifier; its oscilla-tor output, SYNC_OUT, drives the SYNC input of theslave device (U2), synchronizing the switching frequen-cies of the two devices. Synchronizing two MAX9759sensures that no beat frequencies within the audio spec-trum occur on the power-supply rails. This stereo con-figuration works when the master device is in eitherFFM or SSM mode. There is excellent THD+N perfor-mance and minimal crosstalk between devices due tothe SYNC and SYNC_OUT connection (Figures 8, 9).

Multiple MAX9759s can be cascaded and frequencylocked in a similar fashion (Figure 7). Repeat the stereoconfiguration outlined in Figure 7 for multiple cascadingamplifier applications.

Volume ControlIf volume control is required, connect a potentiometerbetween the differential inputs of the MAX9759, as seenin Figure 10. In this configuration, each input “sees”identical RC paths when the device is powered up. Thevariable resistive element appears between the twoinputs, meaning the setting affects both inputs the sameway. This configuration significantly improves transientperformance on power-up or release from SHDN.

IN+

MAX9759

IN-

1µF

1µF

CW

22kΩ

50kΩ

22kΩ

Figure 10. Single-Ended Drive of MAX9759 Plus VolumeControl

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System Diagram

MAX9759

VDD

VDD

VDD

AVDD

1µF

OUT-R8Ω SPEAKER

1µF

1µF

AVSS

IN+

IN-

G2

G1

MUTESHDN

PGNDAVSS

GND

PVDD

VDD

OUT+

OUT-

SYNC

SYNC_OUT

MAX9759

VDD

VDD

1µF

CENTER OUT4Ω SPEAKER

1µF

1µF

AVSS

IN+

IN-

G2

G1

MUTESHDN

PGND GND

PVDD

VDD

OUT+

OUT-

SYNC

SYNC

SYNC_OUT

MAX9759

VDD

VDD

1µF

OUT-L8Ω SPEAKER

1µF

1µF

AVSS

IN+

IN-

G2

G1

MUTESHDN

PGND GND

PVDD

VDD

OUT+

OUT-

SYNC_OUT

OUT-R

EAPDCENTER OUT

OUT-L

2.1AUDIOCODEC

NOTE: SYSTEM DIAGRAM DEPICTS MAX9759 IN SSM MODE WITH fS = 1200 ±70kHz AND +12dB OF GAIN.

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THIN QFN

TOP VIEW

MAX9759

13

14

15

1 2 3 4

5

6

16

12 11 10 9

8

7PGND

SYNC_OUT

G2

V DD

IN+

IN-

GND

OUT+

OUT-

PVDD

G1

SYNC

MUTE

PGND

SHDN

PVDD

Pin Configuration Chip InformationTRANSISTOR COUNT: 4219

PROCESS: BiCMOS

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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.)

24L

QFN

TH

IN.E

PS

PACKAGE OUTLINE,

21-0139 21

E

12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm

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Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses areimplied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

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

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

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,

21-0139 22

E

12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm

evaluation kit 3.2w, high-efficiency, low-emi, …max9759 3.2w, high-efficiency, low-emi,...

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