1.2w, low-emi, filterless, mono class d amplifier with ... · the max9770 combines a mono,...

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,or visit Maxim's website at www.maxim-ic.com.

General DescriptionThe MAX9770 combines a mono, filterless, Class Dspeaker amplifier and stereo DirectDrive® headphoneamplifier in a single device. The MAX9770 operatesfrom a single 2.5V to 5.5V supply and includes featuresthat reduce external component count, system cost,board space, and offer improved audio reproduction.

The speaker amplifier makes use of Maxim’s Class Darchitecture, providing Class AB performance with ClassD efficiency, conserving board space, and extendingbattery life. The speaker amplifier delivers 1.2W into an8Ω load while offering efficiencies above 85%. A spread-spectrum modulation scheme reduces radiated emis-sions caused by the modulation frequency. Furthermore,the MAX9770 oscillator can be synchronized to an exter-nal clock through the SYNC input, avoiding possibleproblem frequencies inside a system. The speakeramplifier features THD+N as low as 0.025%, high 70dBPSRR, and SNR in excess of 90dB.

The headphone amplifiers feature Maxim’s DirectDrivearchitecture that produces a ground-referenced outputfrom a single supply, eliminating the need for large DC-blocking capacitors. The headphone amplifiers deliver upto 80mW into a 16Ω load, feature low 0.015% THD+N,high 85dB PSRR, and ±8kV ESD-protected outputs. Aheadphone sense input detects the presence of a head-phone, and automatically configures the amplifiers foreither speaker or headphone mode.

The MAX9770 includes internally set, logic-selectablegain, and a comprehensive input multiplexer/mixer, allow-ing multiple audio sources to be selected and for truemono reproduction of a stereo source in speaker mode.Industry-leading click-and-pop suppression eliminatesaudible transients during power and shutdown cycles. Alow-power shutdown mode decreases supply currentconsumption to 0.1µA, further extending battery life.

The MAX9770 is offered in space-saving, thermally effi-cient 28-pin TQFN (5mm x 5mm x 0.8mm) and 28-pinTSSOP packages. The MAX9770 features thermal-over-load and output short-circuit protection, and is speci-fied over the extended -40°C to +85°C temperaturerange.

ApplicationsCellular Phones

Compact Notebooks

PDAs

Features♦ 1.2W Filterless Class D Amplifiers Pass FCC

Class B Radiated EMI Standards with 100mmof Cable

♦ Spread-Spectrum Mode Offers 5dB EMIImprovement over Conventional Methods

♦ 80mW DirectDrive Headphone AmplifierEliminates Bulky DC-Blocking Capacitors

♦ High 85dB PSRR at 217Hz♦ 85% Efficiency♦ Low 0.015% THD+N♦ Industry-Leading Click-and-Pop Suppression♦ Integrated 3-Way Input Mixer/Multiplexer

(MAX9770)♦ Logic-Adjustable Gain♦ Short-Circuit and Thermal Protection♦ Available in Space-Saving, Thermally Efficient

Packages

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1.2W, Low-EMI, Filterless, Mono Class D Amplifierwith Stereo DirectDrive Headphone Amplifiers

________________________________________________________________ Maxim Integrated Products 1

SPKR(MONO)

MAX9770

CLASSD

VDD

DirectDriveSTEREO

HEADPHONEIN1L

IN2L

IN1R

IN2R

MONO

GAIN SELINPUT SELMUTESHDNHPS

PART PIN-PACKAGE SELECTABLE INPUTS

MAX9770ETI+ 28 TQFN-EP* 2 stereo, 1 mono

MAX9770EUI 28 TSSOP 2 stereo, 1 mono

Ordering Information

Simplified Block Diagram

19-3134; Rev 2; 4/08

Note: All devices specified over the -40°C to +85°C operatingtemperature range.*EP = Exposed pad.+Denotes a lead-free package.

EVALUATION KITAVAILABLE

Pin Configuration appears at end of data sheet.

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2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS(VDD = PVDD = CPVDD = 3.3V, GND = PGND = CPGND = 0V, SHDN = 3.3V, C1 = C2 = 1µF, CBIAS = 0.047µF, SYNC = GND, RL = ∞,speaker load connected between OUT+ and OUT-, headphone load connected between HPOUT_ and GND, TA = TMIN to TMAX,unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)

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.

GND to PGND to CPGND......................................-0.3V to +0.3VVDD to PVDD to CPVDD..........................................-0.3V to +0.3VVDD to GND ...........................................................................+6VPVDD to PGND.......................................................................+6VCPVDD to CPGND..................................................................+6VCPVSS to CPGND....................................................................-6VSVSS to GND...........................................................................-6VC1N..........................................(PVSS - 0.3V) to (CPGND + 0.3V)HPOUT_ to GND ....................................................................±3VAll Other Pins to GND.................................-0.3V to (VDD + 0.3V)Continuous Current Into/Out of:

PVDD, PGND, OUT_......................................................600mAPVSS ..............................................................................260mA

Duration of HPOUT_ Short Circuit to VDD, PVDD, GND, PGND ...........................................................Continuous

Duration of Short Circuit Between HPOUTL and HPOUTR ..........................................Continuous

Duration of OUT_ Short Circuit to VDD, PVDD, GND, PGND ..10sDuration of Short Circuit Between OUT+ and OUT-...............10sContinuous Power Dissipation (TA = +70°C)

28-Pin TQFN (derate 20.8mW/°C above +70°C) .......1667mW28-Pin TSSOP (derate 12.8mW°C above +70°C) ......1026mW

Junction Temperature ......................................................+150°COperating Temperature Range ...........................-40°C to +85°CStorage Temperature Range .............................-65°C to +150°CLead Temperature (soldering, 10s) .................................+300°C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

GENERAL

Supply Voltage Range VDD Inferred from PSRR test 2.5 5.5 V

Headphone mode 5.5 10Quiescent Supply Current IDD No load

Speaker mode 5.2 7.5mA

Shutdown Supply Current ISHDN SHDN = HPS = GND 0.1 10 µA

Shutdown to Full Operation tON 50 ms

MONO 7 10Input Impedance RIN (Note 3)

INL_, INR_ 14 20kΩ

Bias Voltage VBIAS 1.1 1.25 1.4 V

FeedthroughFrom any unselected input to any output,f = 10kHz

70 dB

SPEAKER AMPLIFIER (GAIN1 = GAIN2 = VDD, HPS = GND)

Output Offset Voltage VOS ±15 ±70 mV

VDD = 2.5V to 5.5V,TA = +25°C

50 70

VRIPPLE = 200mVP-P, f = 217Hz 70

VRIPPLE = 200mVP-P, f = 1kHz 68

Power-Supply Rejection Ratio PSRR (Note 4)


dB

RL = 8Ω 550VDD = 3.3V

RL = 4Ω 900Output Power POUT

f = 1kHz,THD+N = 1%,GAIN1 = 1,GAIN2 = 0 VDD = 5V RL = 8Ω 1200

mW

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ELECTRICAL CHARACTERISTICS (continued)(VDD = PVDD = CPVDD = 3.3V, GND = PGND = CPGND = 0V, SHDN = 3.3V, C1 = C2 = 1µF, CBIAS = 0.047µF, SYNC = GND, RL = ∞,speaker load connected between OUT+ and OUT-, headphone load connected between HPOUT_ and GND, TA = TMIN to TMAX,unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)


RL = 8Ω, POUT = 300mW, f = 1kHz 0.025

RL = 4Ω, POUT = 300mW, f = 1kHz 0.03Total Harmonic Distortion PlusNoise

THD+NRL = 8Ω, POUT = 500mW,f = 1kHz

0.1

%

Signal-to-Noise Ratio SNR RL = 8Ω, VOUT = 2VRMS, A-weighted 85.9 dB

SYNC = GND 980 1100 1220

SYNC = unconnected 1280 1450 1620Output Switching Frequency fS

SYNC = VDD1220

±120kHz

kHz

SYNC Frequency Lock Range 800 2000 kHz

Efficiency η PO = 1000mW, f = 1kHz 85 %

GAIN1 = 0, GAIN2 = 0 6

GAIN1 = 0, GAIN2 = 1 3

GAIN1 = 1, GAIN2 = 0 9Gain (MAX9770) AV

GAIN1 = 1, GAIN2 = 1 0

dB

Gain Accuracy ±5 %

Speaker Path Off-IsolationHPS = VDD, headphone amplifier active,f = 1kHz

102 dB

Into shutdown -76Out of shutdown -55Into mute -83

Click-and-Pop Level KCP

Peak voltage,A-weighted, 32samples per second(Notes 4, 5) Out of mute -69

dB

HEADPHONE AMPLIFIER (GAIN1 = 1, GAIN2 = 0, HPS = VDD)

Output Offset Voltage VOS ±5 ±10 mV

VDD = 2.5V to 5.5V, TA = +25°C 65 76

VRIPPLE = 200mVP-P, f = 217Hz 75

VRIPPLE = 200mVP-P, f = 1kHz 82Power-Supply Rejection Ratio PSRR (Note 4)


dB

RL = 32Ω 40 55VDD = 3.3V

RL = 16Ω 40

RL = 32Ω 60Output Power POUT

TA = +25°C,f = 1kHz,THD+N = 1%(Note 3) VDD = 5V

RL = 16Ω 80

mW

RL = 32Ω, POUT = 50mW, f = 1kHz 0.015Total Harmonic Distortion PlusNoise

THD+NRL = 16Ω, POUT = 35mW, f = 1kHz 0.03

%

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ELECTRICAL CHARACTERISTICS (continued)(VDD = PVDD = CPVDD = 3.3V, GND = PGND = CPGND = 0V, SHDN = 3.3V, C1 = C2 = 1µF, CBIAS = 0.047µF, SYNC = GND, RL = ∞,speaker load connected between OUT+ and OUT-, headphone load connected between HPOUT_ and GND, TA = TMIN to TMAX,unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)


Signal-to-Noise Ratio SNRRL = 32Ω, VOUT = 300mVRMS,BW = 22Hz to 22kHz

101 dB

CrosstalkBetween channels, f = 1kHz,VIN = 200mVP-P

80 dB

Headphone Off-IsolationHPS = GND, speaker amplifier active,f = 1kHz

96 dB

Into shutdown -58Out of shutdown -53Into mute -92

Click-and-Pop Level KCP

Peak voltage, A-weighted, 32samples per second(Notes 4, 5) Out of mute -73

dBV

Capacitive-Load Drive CL 1000 pF

GAIN1 = 0, GAIN2 = 0 7

GAIN1 = 0, GAIN2 = 1 4

GAIN1 = 1, GAIN2 = 0 -2Gain AV

GAIN1 = 1, GAIN2 = 1 1

dB

Gain Accuracy ±2.5 %

ESD Protection HPOUTR, HPOUTL, IEC Air Discharge ±8 kV

DIGITAL INPUTS (SHDN, SYNC, HPS, GAIN_, SEL_)

Input Voltage High VIH 2 V

Input Voltage Low VIL 0.8 V

SYNC input ±25Input Leakage Current (Note 6)

All other logic inputs ±1µA

HPS Input Current HPS = GND -10 µA

Note 1: All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design.Note 2: Speaker amplifier testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For

RL = 4Ω, L = 47µH. For RL = 8Ω, L = 68µH.Note 3: Guaranteed by design, not production tested.Note 4: Inputs AC-coupled to GND.Note 5: Speaker mode testing performed with an 8Ω resistive load in series with a 68µH inductive load connected across BTL output.

Headphone mode testing performed with a 32Ω resistive load connected to GND. Mode transitions are controlled by SHDN. KCPlevel is calculated as: 20 x log [(peak voltage during mode transition, no input signal)/(peak voltage under normal operation atrated power level)]. Units are expressed in dB. Measured with VDD = 5V.

Note 6: SYNC has a 200kΩ resistor to VREF = 1.25V.

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Typical Operating Characteristics(VDD = 3.3V, BW = 22Hz to 22kHz, GAIN1 = 1, GAIN2 = 0, spread-spectrum mode, headphone outputs in phase, unless otherwisenoted.)

10

0.00110 100 10k 100k

TOTAL HARMONIC DISTORTION PLUS NOISEvs. FREQUENCY (SPEAKER MODE)

0.01

0.1

1

MAX

9770

toc0

1

FREQUENCY (Hz)

THD+

N (%

)

1k

VDD = +5VRL = 4Ω

POUT = 25mW

POUT = 1000mW

10

0.00110 100 10k 100k


0.01

0.1

1

MAX

9770

toc0

2

FREQUENCY (Hz)

THD+

N (%

)

1k

RL = 4Ω

POUT = 100mW

POUT = 500mW

10

0.00110 100 10k 100k


0.01

0.1

1

MAX

9770

toc0

3

FREQUENCY (Hz)

THD+

N (%

)

1k

RL = 8Ω

POUT = 40mW

POUT = 400mW

10

0.00110 100 10k 100k


0.01

0.1

1

MAX

9770

toc0

4

FREQUENCY (Hz)

THD+

N (%

)

1k

VDD = 5VPOUT = 1WRL = 8Ω

SSM MODE

FFM MODE

100

0 400 800 1200 1600

10

1

0.1

0.01

0.001

TOTAL HARMONIC DISTORTION PLUS NOISEvs. OUTPUT POWER (SPEAKER MODE)

MAX

9770

toc0

5

OUTPUT POWER (mW)

THD+

N (%

)

VDD = 5VRL = 8Ω

f = 20Hz

f = 1kHz

f = 10kHz

100

0 200 600400 800 1000

10

1

0.1

0.01

0.001


MAX

9770

toc0

6

OUTPUT POWER (mW)

THD+

N (%

)

f = 20Hzf = 1kHz

f = 10kHz

RL = 4Ω

100

0 200 400 600 800

10

1

0.1

0.01

0.001


MAX

9770

toc0

7

OUTPUT POWER (mW)

THD+

N (%

)

RL = 8Ω

f = 20Hz

f = 1kHz

f = 10kHz

100

0 400 800 1200 1600

10

1

0.1

0.01

0.001


MAX

9770

toc0

8

OUTPUT POWER (mW)

THD+

N (%

)

VDD = 5Vf = 1kHzRL = 8Ω

SSM MODE

FFM MODE

1.75

01 10 100

OUTPUT POWERvs. LOAD RESISTANCE (SPEAKER MODE)

0.50

0.25

MAX

9770

toc0

9

LOAD RESISTANCE (Ω)

OUTP

UT P

OWER

(W)

0.75

1.00

1.25

1.50VDD = 5Vf = 1kHz

THD+N = 10%

THD+N = 1%

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Typical Operating Characteristics (continued)(VDD = 3.3V, BW = 22Hz to 22kHz, GAIN1 = 1, GAIN2 = 0, spread-spectrum mode, headphone outputs in phase, unless otherwisenoted.)

1.0

01 10 100

OUTPUT POWERvs. LOAD RESISTANCE (SPEAKER MODE)

0.2

MAX

9770

toc1

0


OUTP

UT P

OWER

(W)

0.4

0.6

0.8

f = 1kHz

THD+N = 10%

THD+N = 1%

2.0

1.5

1.0

0.5

02.5 4.03.0 3.5 4.5 5.0 5.5

OUTPUT POWERvs. SUPPLY VOLTAGE (SPEAKER MODE)

MAX

9770

toc1

1

SUPPLY VOLTAGE (V)

OUTP

UT P

OWER

(W)

f = 1kHzRL = 8Ω

THD+N = 10%

THD+N = 1%

0

30

20

10

50

40

90

80

70

60

100

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

EFFICIENCY vs. OUTPUT POWER

MAX

9770

toc1

2

OUTPUT POWER (W)

EFFI

CIEN

CY (%

)

VDD = 5Vf = 1kHzRL = 8Ω

0

30

20

10

40

50

60

70

80

90

100

0 0.40.2 0.6 0.8 1.0


MAX

9770

toc1

3

OUTPUT POWER (W)

EFFI

CIEN

CY (%

)

RL = 8Ω

RL = 4Ω

f = 1kHz

0

-10

-20

-30

-40

-50

-60

-70

-8010 1k 10k100 100k

POWER-SUPPLY REJECTION RATIOvs. FREQUENCY (SPEAKER MODE)

MAX

9770

toc1

4

FREQUENCY (Hz)

PSRR

(dB)

VRIPPLE = 200mVP-PRL = 8Ω

-140

-100

-120

-60

-80

-20

-40

0

OUTPUT SPECTRUM(SPEAKER MODE)

MAX

9770

toc1

5

FREQUENCY (kHz)

MAG

NITU

DE (d

B)

0 5 10 15 20

RL = 8Ωf = 1kHzFFM MODEVIN = -60dBV

-140

-100

-120

-60

-80

-20

-40

0


MAX

9770

toc1

6

FREQUENCY (kHz)

MAG

NITU

DE (d

B)

0 5 10 15 20

RL = 8Ωf = 1kHzSSM MODEVIN = -60dBV

-160

-100

-120

-140

-60

-80

-20

-40

0


MAX

9770

toc1

7

FREQUENCY (kHz)

MAG

NITU

DE (d

B)

0 5 10 15 20

RL = 8Ωf = 1kHzSSM MODEA-WEIGHTEDVIN = -60dBV

40

-601M 10M 100M

WIDEBAND OUTPUT SPECTRUM(SPEAKER MODE)

-40

MAX

9770

toc1

8

FREQUENCY (Hz)

MAG

NITU

DE (d

BV)

-20

0

20

10

-10

-30

-50

30FFM MODERBW = 10kHz

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1M 10M 100M

WIDEBAND OUTPUT SPECTRUM(SPEAKER MODE)

MAX

9770

toc1

9

FREQUENCY (Hz)

SSM MODERBW = 10kHz

40

-60

-40

MAG

NITU

DE (d

BV)

-20

0

20

10

-10

-30

-50

30

STARTUP WAVEFORM(SPEAKER MODE)

MAX9770 toc20

4ms/div

SHDN2V/div

OUT+ - OUT-500mV/div

RL = 8Ωf = 1kHz

MIXER OUTPUT (SPEAKER MODE)MAX9770 toc21

400μs/div

10kHz1V/div

4kHz1V/div

1kHz2V/div

IN1_

IN2_

MONO

OUT 1V/div

10

0.00110 100 10k 100k

TOTAL HARMONIC DISTORTION PLUS NOISEvs. FREQUENCY (HEADPHONE MODE)

0.01

0.1

1

MAX

9770

toc2

2

FREQUENCY (Hz)

THD+

N (%

)

1k

POUT = 10mW

POUT = 50mW

VDD = 5VRL = 16Ω

10

0.00110 100 10k 100k


0.01

0.1

1

MAX

9770

toc2

3

FREQUENCY (Hz)

THD+

N (%

)

1k

POUT = 10mW

POUT = 50mW

VDD = 5VRL = 32Ω

10

0.00110 100 10k 100k


0.01

0.1

1

MAX

9770

toc2

4

FREQUENCY (Hz)

THD+

N (%

)

1k

POUT = 10mW

POUT = 35mW

RL = 16Ω 10

0.00110 100 10k 100k


0.01

0.1

1

MAX

9770

toc2

5

FREQUENCY (Hz)

THD+

N (%

)

1k

POUT = 10mW

POUT = 50mW

RL = 32Ω

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100

10

1

0.1

0.01

0.0010 50402010 30 60

TOTAL HARMONIC DISTORTION PLUS NOISEvs. OUTPUT POWER (HEADPHONE MODE)

MAX

9770

toc2

8

OUTPUT POWER (mW)

THD+

N (%

)

RL = 16Ω

f = 1kHzf = 10kHz

f = 20Hz

100

10

1

0.1

0.01

0.0010 6020 40 80


MAX

9770

toc2

9

OUTPUT POWER (mW)

THD+

N (%

)

f = 20Hz

RL = 32Ω

f = 1kHzf = 10kHz

100

90

80

70

60

50

40

30

20

10

010 100 1000

OUTPUT POWERvs. LOAD RESISTANCE (HEADPHONE MODE)

MAX

9770

toc3

0


OUTP

UT P

OWER

(mW

)

VDD = 5Vf = 1kHz

THD+N = 10%

THD+N = 1%

80

70

60

50

40

30

20

10

010 100 1000

OUTPUT POWERvs. LOAD RESISTANCE (HEADPHONE MODE)

MAX

9770

toc3

1


OUTP

UT P

OWER

(mW

)f = 1kHz

THD+N = 10%

THD+N = 1%

0

30

20

10

40

50

60

70

80

90

100

2.5 3.53.0 4.0 4.5 5.0 5.5

OUTPUT POWERvs. SUPPLY VOLTAGE (HEADPHONE MODE)

MAX

9770

toc3

2

SUPPLY VOLTAGE (V)

OUTP

UT P

OWER

(mW

)

RL = 16Ωf = 1kHz

THD+N = 10%

THD+N = 1%

0

10

20

30

40

50

60

70

80

2.5 3.53.0 4.0 4.5 5.0 5.5

OUTPUT POWERvs. SUPPLY VOLTAGE (HEADPHONE MODE)

MAX

9770

toc3

3

SUPPLY VOLTAGE (V)

OUTP

UT P

OWER

(mW

)

RL = 32Ωf = 1kHz

THD+N = 10%

THD+N = 1%

0

50

100

150

200

250

300

0 6030 90 120 150

POWER DISSIPATIONvs. OUTPUT POWER (HEADPHONE MODE)

MAX

9770

toc3

4

OUTPUT POWER (mW)

POW

ER D

ISSI

PATI

ON (m

W)

f = 1kHzPOUT = POUTL + POUTR

RL = 16Ω

RL = 32Ω

100

10

1

0.1

0.01

0.0010 40 8020 60 100


MAX

9770

toc2

6

OUTPUT POWER (mW)

THD+

N (%

)

VDD = 5VRL = 16Ω

f = 1kHz

f = 20Hz

f = 10kHz

100

10

1

0.1

0.01

0.0010 6020 40 80


MAX

9770

toc2

7

OUTPUT POWER (mW)

THD+

N (%

)

f = 20Hz

VDD = 5VRL = 32Ω

f = 1kHzf = 10kHz

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POWER-SUPPLY REJECTION RATIOvs. FREQUENCY (HEADPHONE MODE)

MAX

9770

toc3

5

FREQUENCY (Hz)

PSRR

(dB)

10k1k100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

-10010 100k

VDD = 3.3VVRIPPLE = 200mVP-PRL = 32Ω

MAX9770CBIAS = 0.047μF

0

-10010 100 1k 10k 100k

CROSSTALK vs. FREQUENCY (HEADPHONE MODE)

-80

MAX

9770

toc3

6

FREQUENCY (Hz)

CROS

STAL

K (d

B)

-60

-40

-20

-30

-50

-70

-90

-10 RL = 32Ωf = 1kHzVIN = 200mVP-P

LEFT TO RIGHT

RIGHT TO LEFT

0

-10010 100 1k 10k 100k

FEEDTHROUGH vs. FREQUENCY

-80

MAX

9770

toc3

7

FREQUENCY (Hz)

FEED

THRO

UGH

(dB)

-60

-40

-20

-30

-50

-70

-90

-10 SEL1 = 0SEL2 = 1IN1_ = GNDIN2_ = DRIVENVIN = 2VP-P

HEADPHONE MODE

SPEAKER MODE

0

10

30

20

50

40

60

20 30 40 50

OUTPUT POWER vs. CHARGE-PUMP CAPACITANCE

AND LOAD RESISTANCE

MAX

9770

toc3

8


OUTP

UT P

OWER

(mW

)

C1 = C2 = 1μF

C1 = C2 = 0.47μF

f = 1kHzTHD+N = 1%

-140

-100

-120

-60

-80

-20

-40

0

OUTPUT SPECTRUM(HEADPHONE MODE)

MAX

9770

toc3

9

FREQUENCY (kHz)

MAG

NITU

DE (d

B)

0 5 10 15 20

RL = 32Ωf = 1kHzVIN = -60dBV

EXITING SHUTDOWN(HEADPHONE MODE)

MAX9770 toc40

2μs/div

SHDN2V/div

OUT_10mV/div

RL = 32Ω

ENTERING SHUTDOWN(HEADPHONE MODE)

MAX9770 toc41

2μs/div

SHDN2V/div

OUT_10mV/div

RL = 32Ω

0

2

6

4

8

10

SUPPLY CURRENTvs. SUPPLY VOLTAGE

MAX

9770

toc4

2

SUPPLY VOLTAGE (V)

SUPP

LY C

URRE

NT (m

A)

2.5 4.53.5 5.5

SPEAKER MODE

HEADPHONE MODE

0

0.1

0.3

0.2

0.4

0.5

SHUTDOWN SUPPLY CURRENTvs. SUPPLY VOLTAGE

MAX

9770

toc4

3

SUPPLY VOLTAGE (V)

SUPP

LY C

URRE

NT (μ

A)

2.5 4.53.5 5.5

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10 ______________________________________________________________________________________

PIN

TQFN-EP TSSOPNAME FUNCTION

1 4 BIAS Common-Mode Bias Voltage. Bypass with a 0.047µF capacitor to GND.

2 5 VDD Power Supply

3 6 HPOUTR Right-Channel Headphone Output

4 7 HPOUTL Left-Channel Headphone Output

5 8 SVSS Headphone Amplifier Negative Power Supply

6 9 HPS Headphone Sense Input

7 10 CPVDD Positive Charge-Pump Power Supply

8 11 CPVSS Charge-Pump Output. Connect to SVSS.

9 12 C1N Charge-Pump Flying Capacitor Negative Terminal

10 13 C1P Charge-Pump Flying Capacitor Positive Terminal

11 14 CPGND Charge-Pump Ground

12 15 SEL1Select Stereo Channel 1 Inputs. Digital input. Drive SEL1 high to select inputs IN1L andIN1R.

13 16 SEL2Select Stereo Channel 2 Inputs. Digital input. Drive SEL2 high to select inputs IN2L andIN2R.

14 17 SELM Select Mono Channel Input. Digital input. Drive SELM high to select the MONO input.

15 18 SHDNShutdown. Drive SHDN low to disable the device. Connect SHDN to VDD for normaloperation.

16 19 SYNC

Frequency Select and External Clock Input:SYNC = GND: fixed-frequency PWM mode with fS = 1100kHz.SYNC = Unconnected: fixed-frequency PWM mode with fS = 1450kHz.SYNC = VDD: spread-spectrum PWM mode with fS = 1220kHz ±120kHz.SYNC = Clocked: fixed-frequency PWM mode with fS = external clock frequency.

17 20 PGND Speaker Amplifier Power Ground

18 21 OUT+ Speaker Amplifier Positive Output

19 22 OUT- Speaker Amplifier Negative Output

20 23 PVDD Speaker Amplifier Power Supply

21 24 GAIN2 Gain Control Input 2

22 25 GAIN1 Gain Control Input 1

23 26 MONO Mono Channel Input

24 27 IN2L Stereo Channel 2, Left Input

25 28 IN1L Stereo Channel 1, Left Input

26 1 GND Ground

27 2 IN2R Stereo Channel 2, Right Input

28 3 IN1R Stereo Channel 1, Right Input

— — EPExposed Paddle. Can be left unconnected or connected to GND. Connect to groundplane for improved thermal performance.

Pin Description

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______________________________________________________________________________________ 11

OUT+

OUT-

VIN-

VIN+

VOUT+ - VOUT-

tON(MIN)

tSW

Figure 1. MAX9770 Outputs with an Input Signal Applied

Detailed DescriptionThe MAX9770 combines a mono 1.2W Class D speakeramplifiers and stereo 80mW DirectDrive headphoneamplifiers with integrated headphone sensing andcomprehensive click-and-pop suppression. Amixer/multiplexer allows for selection and mixingbetween two stereo input sources and a single monosource. The MAX9770 features PSRR as high as 85dB,THD as low as 0.015%, industry-leading click-and-popsuppression, and a low-power shutdown mode.

Class D Speaker AmplifierThe MAX9770 Class D amplifier features true filterless,low-EMI, switch-mode architecture that provides ClassAB-like performance with Class D eff iciency.Comparators monitor the MAX9770 input and comparethe input voltage to a sawtooth waveform. The com-parators trip when the input magnitude of the sawtoothexceeds the corresponding input voltage. The com-parator resets at a fixed time after the rising edge of the

second comparator trip point, generating a minimum-width pulse tON(MIN) at the output of the second com-parator (Figure 1). As the input voltage increases ordecreases, the duration of the pulse at one outputincreases (the first comparator trip point) while theother output pulse duration remains at tON(MIN). Thiscauses the net voltage across the speaker (VOUT+ -VOUT-) to change.

SYNC INPUT MODE

GND FFPWM with fS = 1100kHz

Unconnected FFPWM with fS = 1450kHz

VDD SSPWM with fS = 1220kHz ±120kHz

Clocked FFPWM with fS = external clock frequency

Table 1. Operating Modes

Operating ModesThe switching frequency of the charge pump is 1/2 theswitching frequency of the Class D amplifier, regard-less of the operating mode. When SYNC is driven exter-nally, the charge pump switches at 1/2 fSYNC. WhenSYNC = VDD, the charge pump switches with a spread-spectrum pattern.

Fixed-Frequency Modulation (FFM) ModeThe MAX9770 features two FFM modes. The FFMmodes are selected by setting SYNC = GND for a1.1MHz switching frequency, and SYNC = unconnect-ed for a 1.45MHz switching frequency. In FFM mode,the frequency spectrum of the Class D output consistsof the fundamental switching frequency and its associ-ated harmonics (see the Wideband Output Spectrum(Speaker Mode) graph in the Typical OperatingCharacteristics). The MAX9770 allows the switching fre-quency to be changed by +32% should the frequencyof one or more harmonics fall in a sensitive band. Thiscan be done during operation and does not affectaudio reproduction.

Spread-Spectrum Modulation (SSM) ModeThe MAX9770 features a unique spread-spectrummode that flattens the wideband spectral components,improving EMI emissions radiated by the speaker andcables by 5dB. Proprietary techniques ensure that thecycle-to-cycle variation of the switching period doesnot degrade audio reproduction or efficiency (see theTypical Operating Characteristics). Select SSM modeby setting SYNC = VDD. In SSM mode, the switchingfrequency varies randomly by ±120kHz around the cen-ter frequency (1.22MHz). The modulation schemeremains the same, but the period of the sawtooth wave-form changes from cycle-to-cycle (Figure 2). Instead ofa large amount of spectral energy present at multiplesof the switching frequency, the energy is now spreadover a bandwidth that increases with frequency. Abovea few MHz, the wideband spectrum looks like whitenoise for EMI purposes (Figure 3).

External Clock ModeThe SYNC input allows the MAX9770 to be synchro-nized to a system clock (allowing a fully synchronoussystem), or allocating the spectral components of theswitching harmonics to insensitive frequency bands.

Applying an external clock of 800kHz to 2MHz to SYNCsynchronizes the switching frequency of both the ClassD and charge pump. The period of the SYNC clock canbe randomized, enabling the MAX9770 to be synchro-nized to another spread-spectrum Class D amplifieroperating in SSM mode.

Filterless Modulation/Common-Mode IdleThe MAX9770 uses Maxim’s unique modulation schemethat eliminates the LC filter required by traditional Class Damplifiers, improving efficiency, reducing componentcount, conserving board space and system cost.Conventional Class D amplifiers output a 50% duty cyclesquare wave when no signal is present. With no filter, thesquare wave appears across the load as a DC voltage,resulting in finite load current, increasing power con-sumption. When no signal is present at the device input,the outputs switch as shown in Figure 4. Because theMAX9770 drives the speaker differentially, the two out-puts cancel each other, resulting in no net idle mode volt-age across the speaker, minimizing power consumption.

EfficiencyThe efficiency of a Class D amplifier is attributed to theregion of operation of the output stage transistors. In aClass D amplifier, the output transistors act as current-steering switches and consume negligible additionalpower. Any power loss associated with the Class D out-put stage is mostly due to the I*R loss of the MOSFETon-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 (typicalmusic reproduction levels), efficiency falls below 30%,whereas the MAX9770 still exhibits > 80% efficienciesunder the same conditions (Figure 5).

DirectDriveTraditional single-supply headphone drivers have theiroutputs biased about a nominal DC voltage (typicallyhalf the supply) for maximum dynamic range. Largecoupling capacitors are needed to block this DC biasfrom the headphone. Without these capacitors, a signif-icant amount of DC current flows to the headphone,resulting in unnecessary power dissipation and possi-ble damage to both headphone and headphone driver.

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12 ______________________________________________________________________________________

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______________________________________________________________________________________ 13

VOUT+ - VOUT-

tSW tSW tSW tSW

VIN-

VIN+

OUT+

OUT-

tON(MIN)

Figure 2. MAX9770 Output with an Input Signal Applied (SSM Mode)

30.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 280.0 300.0220.0200.0 240.0 260.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

AMPL

ITUD

E (d

BμV/

m)

FREQUENCY (MHz)

FCC LIMIT

MAX9770

Figure 3. MAX9770 EMI with 75mm of Speaker Cable

Maxim’s DirectDrive architecture uses a charge pump tocreate an internal negative supply voltage. This allowsthe headphone outputs of the MAX9770 to be biasedabout GND, almost doubling dynamic range while oper-ating from a single supply. With no DC component, thereis no need for the large DC-blocking capacitors. Insteadof two large (220µF, typ) tantalum capacitors, theMAX9770 charge pump requires two small ceramiccapacitors, which conserves board space, reduces cost,and improves the frequency response of the headphonedriver. See the Output Power vs. Charge-PumpCapacitance and Load Resistance graph in the TypicalOperating Characteristics for details of the possiblecapacitor sizes. There is a low DC voltage on the driveroutputs due to amplifier offset. However, the offset of theMAX9770 is typically 5mV, which, when combined with a32Ω load, results in less than 160µA of DC current flowto the headphones.

In addition to the cost and size disadvantages of the DC-blocking capacitors required by conventional head-phone amplifiers, these capacitors limit the amplifier’slow-frequency response and can distort the audio signal.

Previous attempts at eliminating the output-couplingcapacitors involved biasing the headphone return(sleeve) to the DC bias voltage of the headphoneamplifiers. This method raises some issues:

1) When combining a microphone and headphone on asingle connector, the microphone bias scheme typi-cally requires a 0V reference.

2) The sleeve is typically grounded to the chassis.Using the midrail biasing approach, the sleeve mustbe isolated from system ground, complicating prod-uct design.

3) During an ESD strike, the driver’s ESD structures arethe only path to system ground. Thus, the drivermust be able to withstand the full ESD strike.

4) When using the headphone jack as a line out toother equipment, the bias voltage on the sleeve mayconflict with the ground potential from other equip-ment, resulting in possible damage to the drivers.

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14 ______________________________________________________________________________________

0

30

20

10

50

40

90

80

70

60

100

0 0.1 0.2 0.40.3 0.5 0.6


OUTPUT POWER (W)

EFFI

CIEN

CY (%

)

MAX9770

CLASS ABVDD = 3.3Vf = 1kHzRL - 8Ω

Figure 5. MAX9770 Efficiency vs. Class AB Efficiency

MAX9770

800kΩ

10kΩ10kΩ

VDD

HPS

HPOUTL

HPOUTR

SHUTDOWNCONTROL

SHDN

Figure 6. HPS Configuration

VIN = 0V

OUT-

OUT+

VOUT+ - VOUT- = 0V

Figure 4. MAX9770 Output with No Signal Applied

Charge PumpThe MAX9770 features a low-noise charge pump. Theswitching frequency of the charge pump is 1/2 theswitching frequency of the Class D amplifier, regardlessof the operating mode. When SYNC is driven externally,the charge pump switches at 1/2 fSYNC. When SYNC =VDD, the charge pump switches with a spread-spectrumpattern. The nominal switching frequency is well beyondthe audio range, and thus does not interfere with theaudio signals, resulting in an SNR of 101dB. The switchdrivers feature a controlled switching speed that mini-mizes noise generated by turn-on and turn-off tran-sients. By limiting the switching speed of the chargepump, the di/dt noise caused by the parasitic bond wireand trace inductance is minimized. Although not typical-ly required, additional high-frequency noise attenuationcan be achieved by increasing the size of C2 (see theBlock Diagram). The charge pump is active in bothspeaker and headphone modes.

Input Multiplexer/MixerThe MAX9770 features an input multiplexer/mixer thatallows multiple audio sources to be selected/mixed.Driving a SEL_ input high selects the input channel (seeTable 2), and the audio signal is output to the activeamplifier. When a stereo path is selected in speakermode, the left and right inputs are attenuated by 6dB andmixed together, resulting in a true mono reproduction of astereo signal. When more than one signal path is select-ed, the sources are attenuated before mixing to preserveoverall amplitude. For example, selecting two sources inheadphone mode results in 6dB attenuation of the inputs,while selecting three sources in headphone mode resultsin 9.5dB attenuation of the inputs. Table 2 shows how theinput signals are attenuated and mixed for each possibleinput selection combination.

Headphone Sense Input (HPS)The headphone sense input (HPS) monitors the head-phone jack, and automatically configures the devicebased upon the voltage applied at HPS. A voltage ofless than 0.8V sets the device to speaker mode. A volt-age of greater than 2V disables the bridge amplifiersand enables the headphone amplifiers.

For automatic headphone detection, connect HPS to thecontrol pin of a 3-wire headphone jack as shown inFigure 6. With no headphone present, the output imped-ance of the headphone amplifier pulls HPS to less than0.8V. When a headphone plug is inserted into the jack,the control pin is disconnected from the tip contact andHPS is pulled to VDD through the internal 800kΩ pullup.When driving HPS from an external logic source, groundHPS when the MAX9770 is shut down. Place a 10kΩresistor in series with HPS and the headphone jack toensure ±8kV ESD protection.

BIASThe MAX9770 features internally generated, power-sup-ply independent, common-mode bias voltages refer-enced to GND. BIAS provides both click-and-popsuppression and sets the DC bias level for the amplifiers.Choose the value of the bypass capacitor as described inthe BIAS Capacitor section. No external load should beapplied to BIAS. Any load lowers the BIAS voltage, affect-ing the overall performance of the device.

Gain SelectionThe MAX9770 features logic-selectable, internally setgains. GAIN1 and GAIN2 set the gain of the MAX9770speaker and headphone amplifiers as shown in Table 3.

The MAX9770 can be configured to automaticallyswitch between two gain settings depending onwhether the device is in speaker or headphone mode.By driving one or both gain inputs with HPS, the gain of

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Table 2. MAX9770 Multiplexer/Mixer SettingsHEADPHONE MODE

SEL1 SEL2 SELMHPOUTL HPOUTR

SPEAKER MODE

0 0 0 MUTE MUTE MUTE

1 0 0 IN1L IN1R (IN1L + IN1R) / 2

0 1 0 IN2L IN2R (IN2L + IN2R) / 2

0 0 1 MONO MONO MONO

1 1 0 (IN1L + IN2L) / 2 (IN1R + IN2R) / 2 (IN1L + IN1R + IN2L + IN2R) / 4

1 0 1 (IN1L + MONO) /2 (IN1R + MONO) / 2 (IN1L + IN1R + MONO x 2) / 4

0 1 1 (IN2L + MONO) / 2 (IN2R + MONO) / 2 (IN2L + IN2R + MONO x 2) / 4

1 1 1 ( IN 1L + IN 2L + M ON O) / 3 ( IN 1R + IN 2R + M ON O) / 3 ( IN1L + IN 1R + IN 2L + IN 2R + M ON O x 2) / 6

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the device changes when a headphone is inserted orremoved. For example, the block diagram shows HPSconnected to GAIN2, while GAIN1 is connected to VDD.In this configuration, the gain in speaker mode is 9dB,while the gain in headphone mode is 1dB. The gainsettings with the HPS connection are shown in Table 4.

ShutdownThe MAX9770 features a 0.1µA, low-power shutdownmode that reduces quiescent current consumption andextends battery life. Drive SHDN low to disable thedrive amplifiers, bias circuitry, and charge pump. Biasis driven to GND and the headphone amplifier outputimpedance is 10kΩ in shutdown. Connect SHDN toVDD for normal operation.

Click-and-Pop SuppressionSpeaker Amplifier

The MAX9770 speaker amplifier features comprehen-sive click-and-pop suppression that eliminates audibletransients on startup and shutdown. While in shutdown,the H-bridge is in a high-impedance state. During start-

up or power-up, the input amplifiers are muted and aninternal loop sets the modulator bias voltages to the cor-rect levels, preventing clicks and pops when the H-bridge is subsequently enabled. A soft-start functionunmutes the input amplifiers 30ms after startup.

Headphone AmplifierIn conventional single-supply headphone drivers, theoutput-coupling capacitor is a major contributor ofaudible clicks and pops. Upon startup, the drivercharges the coupling capacitor to its bias voltage, typi-cally half the supply. Likewise, during shutdown, thecapacitor is discharged to GND. This results in a DCshift across the capacitor, which in turn, appears as anaudible transient at the speaker. Since the MAX9770headphone amplifier does not require output-couplingcapacitors, this does not arise.

Additionally, the MAX9770 features extensive click-and-pop suppression that eliminates any audible transientsources internal to the device. The Exiting Shutdown(Headphone Mode) and Entering Shutdown (HeadphoneMode) graphs in the Typical Operating Characteristicsshows that there are minimal spectral components in theaudible range at the output upon startup or shutdown.

In most applications, the output of the preamplifier dri-ving the MAX9770 has a DC bias of typically half thesupply. During startup, the input-coupling capacitor ischarged to the preamplifier’s DC bias voltage throughthe RF of the MAX9770, resulting in a DC shift across thecapacitor and an audible click-and-pop. An internaldelay of 50ms eliminates the click-and-pop caused bythe input filter.

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) at idle and causes large ripple currents.Any parasitic resistance in the filter components resultsin a loss of power, lowering efficiency.

The MAX9770 does not require an output filter. Thedevice relies on the inherent inductance of the speakercoil and the natural filtering of both the speaker and thehuman ear to recover the audio component of thesquare-wave output. Eliminating the output filter results ina smaller, less costly, and more efficient solution.

Because the frequency of the MAX9770 output is wellbeyond the bandwidth of most speakers, voice coilmovement due to the square-wave frequency is minimal.


16 ______________________________________________________________________________________

Table 3. Gain Selection

GAIN1 GAIN2MAX9770

SPEAKER GAIN(dB)

HEADPHONEGAIN(dB)

0 0 6 7

0 1 3 4

1 0 9 -2

1 1 0 1

Table 4. Gain Settings with HPSConnection

G A I N 1 G A I N 2

MAX9770 SPEAKERMODE GAIN

(HPS = 0)(dB)

HEADPHONE MODEGAIN

(HPS = 1)(dB)

HPS 0 6 -2

HPS 1 3 1

0 HPS 6 4

1 HPS 9 1

HPS HPS 6 1

0 0 6 7

0 1 3 4

1 0 9 -2

1 1 0 1

Although this movement is small, a speaker not designedto handle the additional power may be damaged. Foroptimum results, use a speaker with a series inductance>10µH. Typical small 8Ω speakers exhibit series induc-tances in the range of 20µH to 100µH.

Output OffsetUnlike Class AB amplifiers, 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, a15mV DC offset across an 8Ω load results in 1.9mA extracurrent consumption in a Class AB device. In the Class Dcase, a 15mV offset into 8Ω equates to an additionalpower drain of 28µW. Due to the high efficiency of theClass D amplifier, this represents an additional quiescentcurrent draw of 28µW/(VDD / 100 x η), which is on theorder of a few microamps.

Power SuppliesThe MAX9770 has different supplies for each portion ofthe device, allowing for the optimum combination ofheadroom and power dissipation and noise immunity.The speaker amplifier is powered from PVDD. PVDDranges from 2.5V to 5.5V. The headphone amplifiersare powered from VDD and SVSS. VDD is the positivesupply of the headphone amplifiers and ranges from2.5V to 5.5V. SVSS is the negative supply of the head-phone amplifiers. Connect SVSS to CPVSS. The chargepump is powered by CPVDD. CPVDD ranges from 2.5Vto 5.5V and should be the same potential as VDD. Thecharge pump inverts the voltage at CPVDD, and theresulting voltage appears at CPVSS. The remainder ofthe device is powered by VDD.

Component SelectionInput Filter

The input capacitor (CIN), in conjunction with the ampli-fier input resistance (RIN), forms a highpass filter thatremoves the DC bias from an incoming signal (see theBlock Diagram). The AC-coupling capacitor allows theamplifier to bias the signal to an optimum DC level.Assuming zero-source impedance, the -3dB point ofthe highpass filter is given by:

RIN is the amplifier’s internal input resistance valuegiven in the Electrical Characteristics. Be aware thatthe MONO input has a lower input impedance than theother inputs. Choose CIN such that f-3dB is below thelowest frequency of interest. Setting f-3dB too high

affects the amplifier’s low-frequency response. Settingf-3dB too low can affect the click-and-pop performance.Use capacitors with low-voltage coefficient dielectrics,such as tantalum or aluminum electrolytic. Capacitorswith high-voltage coefficients, such as ceramics, mayresult in increased distortion at low frequencies.

Output FilterThe MAX9770 speaker amplifier does not require an out-put filter for normal operation and audio reproduction. Thedevice passes FCC Class B radiated emissions stan-dards with 100mm of unshielded speaker cables.However, output filtering can be used if a design is failingradiated emissions due to board layout or cable length,or if the circuit is near EMI-sensitive devices. Use a com-mon-mode choke connected in series with the speakeroutputs if board space is limited and emissions are aconcern. Use of an LC filter is necessary if excessivespeaker cable is used.

BIAS CapacitorBIAS is the output of the internally generated DC biasvoltage. The BIAS bypass capacitor, CBIAS improvesPSRR and THD+N by reducing power supply and othernoise sources at the common-mode bias node, andalso generates the clickless/popless, startup/shutdownDC bias waveforms for the speaker amplifiers. BypassBIAS with a 0.047µF capacitor to GND.

fR CdB

IN IN− =3

12

π

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Charge-Pump Capacitor SelectionUse capacitors with an ESR less than 100mΩ for opti-mum performance. Low-ESR ceramic capacitors mini-mize the output resistance of the charge pump. Mostsurface-mount ceramic capacitors satisfy the ESRrequirement. For best performance over the extendedtemperature range, select capacitors with an X7Rdielectric. Table 5 lists suggested manufacturers.

Flying Capacitor (C1)The value of the flying capacitor (C1) affects the loadregulation and output resistance of the charge pump. AC1 value that is too small degrades the device’s ability toprovide sufficient current drive, which leads to a loss ofoutput voltage. Increasing the value of C1 may improveload regulation and reduces the charge-pump outputresistance to an extent. Above 1µF, the on-resistance ofthe switches and the ESR of C1 and C2 dominate.

Output Capacitor (C2)The output capacitor value and ESR directly affect theripple at CPVSS. Increasing the value of C2 reducesoutput ripple. Likewise, decreasing the ESR of C2reduces both ripple and output resistance. Lowercapacitance values can be used in systems with lowmaximum output power levels. See the Output Powervs. Charge-Pump Capacitance and Load Resistancegraph in the Typical Operating Characteristics.

CPVDD Bypass CapacitorThe CPVDD bypass capacitor (C3) lowers the outputimpedance of the power supply and reduces the impactof the MAX9770’s charge-pump switching transients.Bypass CPVDD with C3, the same value as C1, andplace it physically close to the CPVDD and PGND (referto the MAX9770 EV kit for a suggested layout).

Layout and GroundingProper layout and grounding are essential for optimumperformance. Use large traces for the power-supplyinputs and amplifier outputs to minimize losses due to

parasitic trace resistance, as well as route the headaway from the device. Good grounding improves audioperformance, minimizes crosstalk between channels,and prevents any switching noise from coupling into theaudio signal. Connect CPGND, PGND, and GNDtogether at a single point on the PC board. RouteCPGND and all traces that carry switching transientsaway from GND, PGND, and the traces and compo-nents in the audio signal path.

Connect all components associated with the chargepump (C2 and C3) to the CPGND plane. Connect SVSSand CPVSS together at the device. Place the charge-pump capacitors (C1, C2, and C3) as close to thedevice as possible. Bypass VDD and PVDD with a 1µFcapacitor to GND. Place the bypass capacitors asclose to the device as possible.

Use large, 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.Large output, supply, and GND traces also improve thepower dissipation of the device.

The MAX9770 thin QFN package features an exposedthermal pad on its underside. This pad lowers the pack-age’s thermal resistance by providing a direct heat con-duction path. Due to the high efficiency of the MAX9770’sClass D amplifier, additional heatsinking is not required. Ifadditional heatsinking is required, connect the exposedpaddle to GND. See the MAX9770 EV kit data sheet forsuggested component values and layout guidelines.


18 ______________________________________________________________________________________

Table 5. Suggested Capacitor ManufacturersSUPPLIER PHONE FAX WEBSITE

Taiyo Yuden 800-348-2496 847-925-0899 www.t-yuden.com

TDK 807-803-6100 847-390-4405 www.component.tdk.com

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Block Diagram

HPS

IN1L

GAIN2HPS

VDD

VDD

GND

GND

VDD

GAIN1

SELM

SEL1

VDDCPVDD

C1P

C1N

CPVSS SVSS GND

OSC/2C11μF

CIN0.47μF

C21μF

1μF

CPGND

SYNC

25(28)

21(24)22(25)14(17)12(15)13(16)

10(13)

7(10)

9(12)

11(14)

8(11)

5(8)

26(1)

16(19) 20

(23)

18(21)

2(5)

19(22)

6(9)

4(7)

3(6)

HPOUTL

HPOUTR

1μF

0.1μF2.5V TO 5.5V

MIXER/MUX/GAINCONTROL

LEFT-CHANNELAUDIO INPUT 1

IN1R

CIN0.47μF 28

(3)RIGHT-CHANNELAUDIO INPUT 1

MONO

CIN1μF 23

(26)MONOAUDIO INPUT

IN2L

CIN0.47μF 24

(27)LEFT-CHANNELAUDIO INPUT 2

IN2R

CIN0.47μF 27

(2)RIGHT-CHANNELAUDIO INPUT 2

CHARGEPUMP

MUX ANDGAIN CONTROL

HEADPHONEDETECTION

SHUTDOWNCONTROL

OSCILLATOR

H-BRIDGE

VDD

OUT+

PVDD

2.5V TO 5.5V

VDD

OUT-17

(20) PGND

VDD

SEL2

15(18)SHDN

( ) FOR TSSOP PIN.

CBIAS0.047μF

CLASS DMODULATOR

MAX9770

1(4) BIAS

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System Diagram

AUDIO DAC

MAX9770

IN1L

2.5V TO 5.5V

2.5V TO 5.5V

IN1R

1μF

1μF

0.47μF

0.47μF

GND PGND

OUT+

OUT-

HPOUTL

HPS

HPOUTR

VDD HPVDD

FM RADIOMODULE

IN2L

IN2R

0.47μF

0.47μF

BASEBANDPROCESSOR

SHDN

MONO

1μF

SEL1SEL2SELM

VDD GAIN1

VDD GAIN2

1μF

0.047μF

BIAS

CPVSS

CPVDD

SVSS

CPGND

C1P

C1N

1μF1μF

PVDD

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Pin Configurations

28

27

26

25

24

23

22

21

20

19

18

17

16

15

1

2

3

4

5

6

7

8

9

10

11

12

13

14

IN1L

IN2L

MONO

GAIN1

GAIN2

PVDD

SEL1

OUT-

OUT+

PGND

SYNC

SHDN

SELM

SEL2

CPGND

C1P

C1N

CPVSS

CPVDD

HPS

SVSS

HPOUTL

HPOUTR

VDD

BIAS

IN1R

IN2R

GND

TSSOP

TOP VIEW

MAX9770

28

27

26

25

24

23

22

IN1R

IN2R

GND

IN1L

IN2L

MONO

GAIN1

8

9

10

11

12

13

14

CPVSS

C1N

C1P

CPGND

SEL1

SEL2

SELM

15161718192021

SHDN

SYNC

PGND

OUT+

OUT-

PVDD

GAIN

2

7654321

CPV D

D

HPS

SVSS

HPOU

TL

HPOU

TRV DD

BIAS

MAX9770

TQFN

Chip InformationTRANSISTOR COUNT: 7020

PROCESS: BiCMOS

Package InformationFor the latest package outline information, go towww.maxim-ic.com/packages.

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

28 TQFN-EP T2855N-1 21-0140

28 TSSOP U28-1 21-0066

http://pdfserv.maxim-ic.com/package_dwgs/21-0140.PDF

http://pdfserv.maxim-ic.com/package_dwgs/21-0066.PDF

MA

X9

77

0


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.

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

© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

Revision History

REVISIONNUMBER

REVISIONDATE

DESCRIPTIONPAGES

CHANGED

2 4/08 Removing MAX9772 from data sheet 1–21

1.2w, low-emi, filterless, mono class d amplifier with ... · the max9770 combines a mono,...

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