MAX9750AETI+T ,2.6W Stereo Audio Power Amplifiers and DirectDrive® Headphone AmplifiersMAX9750/MAX9751/MAX975519-3006; Rev 8; 6/08EVALUATION KITAVAILABLE2.6W Stereo Audio Power Amplifier ..
MAX9750CETI ,2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiersfeatures a 2:1 input multiplexer,♦ Low-Power Shutdown Modeallowing multiple audio sources to be sel ..
MAX9750CETI+ ,2.6W Stereo Audio Power Amplifiers and DirectDrive® Headphone AmplifiersBlock Diagrams continued at end of data sheet.____ Maxim Integrated Products 1For pricing, delivery ..
MAX9750CETI+ ,2.6W Stereo Audio Power Amplifiers and DirectDrive® Headphone AmplifiersApplications♦ ±8kV ESD-Protected Headphone Driver OutputsNotebook PCs Flat-Panel TVs♦ Available in ..
MAX9750CETI+C2U ,2.6W Stereo Audio Power Amplifiers and DirectDrive® Headphone AmplifiersBlock Diagrams continued at end of data sheet.____ Maxim Integrated Products 1For pricing, delivery ..
MAX9750CETI+T ,2.6W Stereo Audio Power Amplifiers and DirectDrive® Headphone AmplifiersFeaturesThe MAX9750/MAX9751/MAX9755 combine a stereo,♦ No DC-Blocking Capacitors Required—Provides® ..
MB89475 ,F2MC-8L/Low Power/Low Voltage Microcontrollersapplications forconsumer product.2* : F MC stands for FUJITSU Flexible Microcontroller.n
MB89535A ,F2MC-8L/Low Power/Low Voltage MicrocontrollersFEATURES• Wide range of package options• Two types of QFP packages (1 mm pitch, 0.65 mm pitch) • LQ ..
MB89535A ,F2MC-8L/Low Power/Low Voltage MicrocontrollersFUJITSU SEMICONDUCTORDS07-12547-4EDATA SHEET8-bit Original Microcontroller CMOS2F MC-8L MB89530A Se ..
MB89537A , 8-bit Original Microcontroller CMOS, F-2MC-8L MB89530A Series
MB89537A , 8-bit Original Microcontroller CMOS, F-2MC-8L MB89530A Series
MB89537AC , 8-bit Original Microcontroller CMOS, F-2MC-8L MB89530A Series
MAX9750AETI+-MAX9750AETI+T-MAX9750CETI+-MAX9750CETI+C2U-MAX9750CETI+T-MAX9755ETI+-MAX9755ETI+T
2.6W Stereo Audio Power Amplifiers and DirectDrive® Headphone Amplifiers
General DescriptionThe MAX9750/MAX9751/MAX9755 combine a stereo,
2.6W audio power amplifier and stereo DirectDrive®
110mW headphone amplifier in a single device. The
headphone amplifier uses Maxim’s DirectDrive architec-
ture that produces a ground-referenced output from a
single supply, eliminating the need for large DC-blocking
capacitors, saving cost, space, and component height.
A high 90dB PSRR and low 0.01% THD+N ensures
clean, low-distortion amplification of the audio signal.
The MAX9750 features an analog volume control, and a
BEEP input. The MAX9751 features a 2:1 input multiplexer,
allowing multiple audio sources to be selected. All devices
feature a single-supply voltage, a shutdown mode, logic-
selectable gain, and a headphone sense input. Industry-
leading click-and-pop suppression eliminates audible
transients during power and shutdown cycles.
The MAX9750/MAX9751/MAX9755 are offered in a
space-saving, thermally efficient 28-pin thin QFN (5mm
x 5mm x 0.8mm) package. These devices have thermal-
overload and output short-circuit protection, and are
specified over the extended -40°C to +85°C tempera-
ture range.
ApplicationsNotebook PCsFlat-Panel TVs
Tablet PCsPC Displays
Portable DVD PlayersLCD Projectors
FeaturesNo DC-Blocking Capacitors Required—Provides
Industry’s Most Compact Notebook Audio
SolutionPC2001 Compliant5V Single-Supply OperationClass AB 2.6W Stereo BTL Speaker Amplifiers110mW DirectDrive Headphone AmplifiersHigh 90dB PSRRLow-Power Shutdown ModeIndustry-Leading Click-and-Pop SuppressionLow 0.01% THD+N at 1kHzShort-Circuit and Thermal ProtectionSelectable Gain Settings Analog Volume Control (MAX9750)BEEP Input with Glitch Filter (MAX9750)2:1 Stereo Input MUX (MAX9751)±8kV ESD-Protected Headphone Driver OutputsAvailable in Space-Saving, Thermally Efficient
28-Pin Thin QFN (5mm x 5mm x 0.8mm) Package
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Ordering Information19-3006; Rev 8; 6/08
EVALUATION KIT
AVAILABLE
PART*PIN-
PACKAGEA XIM U M GA IN d B )
MAX9750AETI+28 Thi n QFN 13.5
MAX9750BETI+28 Thi n QFN 19.5
MAX9750CETI+28 Thi n QFN 10.5
MAX9751ETI+28 Thi n QFN 10.5
MAX9755ETI+28 Thi n QFN 10.5
+Denotes a lead-free/RoHS-compliant package.
*All devices specified over the -40°C to +85°C temperature
range.
VOL
BEEP
MAX9750
Simplified Block DiagramsDirectDrive is a registered trademark of Maxim Integrated
Products, Inc.
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ABSOLUTE MAXIMUM RATINGSStresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Supply Voltage (VDD, PVDD, HPVDD, CPVDDto GND)..........+6V
GND to PGND.....................................................................±0.3V
CPVSS, C1N, VSSto GND.........................-6.0V to (GND + 0.3V)
HPOUT_ to GND....................................................................±3V
Any Other Pin.............................................-0.3V to (VDD+ 0.3V)
Duration of OUT_ Short Circuit to GND or PVDD........Continuous
Duration of OUT_+ Short Circuit to OUT_-.................Continuous
Duration of HPOUT_ Short Circuit to GND,
VSSor HPVDD.........................................................Continuous
Continuous Current (PVDD, OUT_, PGND)...........................1.7A
Continuous Current (CPVDD, C1N, C1P, CPVSS, VSS, HPVDD,
HPOUT_).......................................................................850mA
Continuous Input Current (All Other Pins)........................±20mA
Continuous Power Dissipation (TA= +70°C, multilayer board)
28-Pin Thin QFN (derate 23.8mW/°C above +70°C).1900mW
Junction-to-Case Thermal Resistance (θJC)
28-Pin Thin QFN...........................................................24°C/W
Junction Temperature......................................................+150°C
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
ELECTRICAL CHARACTERISTICS(VDD= PVDD= CPVDD= HPVDD= 5V, VGND= VPGND= VCPGND= 0V, SHDN= VDD, CBIAS= 1µF, C1 = C2 = 1µF, speaker load
terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, VGAIN1= VGAIN2= VVOL= VGAIN= 0V,= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
GENERALSupply Voltage RangeVDD, PVDDInferred from PSRR test4.55.5V
Headphone Supply VoltageCPVDD,
HPVDDInferred from PSRR test3.05.5V
HPS = GND, speaker mode, RL = ∞1429Quiescent Supply CurrentIDDHPS = VDD, headphone mode, RL = ∞713mA
Shutdown Supply CurrentISHDNSHDN = GND0.25µA
Bias VoltageVBIAS1.71.81.9V
Switching TimetSWGain or input switching10µs
MAX9750102030Input ResistanceRINAmplifier inputs
(Note 2)MAX9751/MAX97554.568.0kΩ
Turn-On TimetSON25ms
SPEAKER AMPLIFIER (HPS = GND)MAX9750A/MAX9750B/
MAX9751/MAX9755±1±15
Output Offset VoltageVOS
Measured
between OUT_+
and OUT_-,
TA = +25°CMAX9750C±0.4±6
MAX9750A/MAX9750B/
MAX9750C/MAX97517590PVDD or VDD =
4.5V to 5.5V
(TA = +25°C)MAX97557290
f = 1kHz, VRIPPLE = 200mVP-P80
Power-Supply Rejection Ratio
(Note 3)PSRR
f = 10kHz, VRIPPLE = 200mVP-P55
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ELECTRICAL CHARACTERISTICS (continued)(VDD= PVDD= CPVDD= HPVDD= 5V, VGND= VPGND= VCPGND= 0V, SHDN= VDD, CBIAS= 1µF, C1 = C2 = 1µF, speaker load
terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, VGAIN1= VGAIN2= VVOL= VGAIN= 0V,= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSMAX9750A/
MAX9750B/
MAX9751/
MAX9755
0.91.4RL = 8Ω
MAX9750C0.650.8
MAX9750A/
MAX9750B/
MAX9751/
MAX9755
RL = 4Ω
MAX9750C1.21.5
MAX9750A/
MAX9750B/
MAX9751/
MAX9755
Output Power (Note 4)POUT
THD+N = 1%,
f = 1kHz,
TA = +25°C
RL = 3Ω
MAX9750C2.2
RL = 8Ω, POUT = 500mW, f = 1kHz0.01Total Harmonic Distortion Plus
NoiseTHD+NRL = 4Ω, POUT = 1W, f = 1kHz0.02%
Signal-to-Noise RatioSNRRL = 8Ω, POUT = 500mW, BW = 22Hz to
22kHz96dB
NoiseVnBW = 22Hz to 22kHz, A-weighted22µVRMS
Capacitive-Load DriveCLNo sustained oscillations200pF
CrosstalkL to R, R to L, f = 10kHz75
Off-IsolationAny unselected input to any active input,
f = 10kHz (MAX9751), input referred75dB
Slew RateSR1.4V/µs
GAIN1 = 0, GAIN2 = 09
GAIN1 = 1, GAIN2 = 010.5
GAIN1 = 0, GAIN2 = 112MAX9750A
GAIN1 = 1, GAIN2 = 113.5
GAIN1 = 0, GAIN2 = 015
GAIN1 = 1, GAIN2 = 016.5
GAIN1 = 0, GAIN2 = 118MAX9750B
GAIN1 = 1, GAIN2 = 119.5
GAIN1 = 0, GAIN2 = 06
GAIN1 = 1, GAIN2 = 07.5
GAIN1 = 0, GAIN2 = 19
Gain (Maximum Volume Setting)AVMAX(SPKR)
MAX9750C
GAIN1 = 1, GAIN2 = 110.5
GAIN = 19Gain (MAX9751/MAX9755)AVGAIN = 010.5dB
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ELECTRICAL CHARACTERISTICS (continued)(VDD= PVDD= CPVDD= HPVDD= 5V, VGND= VPGND= VCPGND= 0V, SHDN= VDD, CBIAS= 1µF, C1 = C2 = 1µF, speaker load
terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, VGAIN1= VGAIN2= VVOL= VGAIN= 0V,= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
HEADPHONE AMPLIFIER (HPS = VDD)Output Offset VoltageVOSTA = +25°C±2±7mV
HPVDD = 3V to 5.5V, TA = +25°C6075
f = 1kHz, VRIPPLE = 200mVP-P73Power-Supply Rejection Ratio
(Note 3)PSRR
f = 10kHz, VRIPPLE = 200mVP-P63
RL = 32Ω4050
Output PowerPOUTTHD+N = 1%,
f = 1kHz, TA = +25°CRL = 16Ω110
RL = 32Ω, POUT = 20mW, f = 1kHz0.007Total Harmonic Distortion Plus
NoiseTHD+NRL = 16Ω, POUT = 75mW, f = 1kHz0.03%
Signal-to-Noise RatioSNRRL = 32Ω, POUT = 50mW, BW = 22Hz to
22kHz101dB
NoiseVnBW = 22Hz to 22kHz11µVRMS
Capacitive-Load DriveCLNo sustained oscillations200pF
CrosstalkL to R, R to L, f = 10kHz88
Off-IsolationAny unselected input to any active input,
f = 10kHz (MAX9751), input referred74dB
Slew RateSR0.4V/µs
ESDESDIEC air discharge±8kV
GAIN2 = GAIN = 0, GAIN1 = X3GainAVGAIN2 = GAIN = 1, GAIN1 = X0dB
CHARGE PUMPCharge-Pump FrequencyfOSC500550600kHz
VOLUME CONTROL (MAX9750_)VOL Input ImpedanceRVOL100MΩ
VOL Input Hysteresis10mV
Full Mute Input Voltage(Note 5)0.858 x
HPVDDV
Channel MatchingAV = -25dB to +13.5dB±0.2dB
BEEP INPUT (MAX9750_)Beep Signal Minimum AmplitudeVBEEPRB = 33kΩ (Note 6)0.8VP-P
Beep Signal Minimum FrequencyfBEEP300Hz
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ELECTRICAL CHARACTERISTICS (continued)(VDD= PVDD= CPVDD= HPVDD= 5V, VGND= VPGND= VCPGND= 0V, SHDN= VDD, CBIAS= 1µF, C1 = C2 = 1µF, speaker load
terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, VGAIN1= VGAIN2= VVOL= VGAIN= 0V,= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
LOGIC INPUT (SHDN, GAIN1, GAIN2, GAIN, VOL, IN1/2)Logic Input High VoltageVIH2V
Logic Input Low VoltageVIL0.8V
Logic Input CurrentIIN±1µA
LOGIC INPUT HEADPHONE (HPS)Logic Input High VoltageVIH2V
Logic Input Low VoltageVIL0.8V
Logic Input CurrentIIN10µA
Note 1:All devices are 100% production tested at room temperature. All temperature limits are guaranteed by design.
Note 2:Guaranteed by design. Not production tested.
Note 3:PSRR is specified with the amplifier input connected to GND through CIN.
Note 4:Output power levels are measured with the thin QFN’s exposed paddle soldered to the ground plane.
Note 5:See Table 3 for details of the mute levels.
Note 6:The value of RBdictates the minimum beep signal amplitude (see the Beep Inputsection).
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Typical Operating Characteristics(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
0.00011k10k100100k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (SPEAKER MODE)MAX9750/51 toc01
FREQUENCY (Hz)
THD+N (%)
VCC = 5V
RL = 3Ω
AV = 10.5dB
OUTPUT POWER = 1.5W
OUTPUT POWER = 500mW
0.00011k10k100100k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (SPEAKER MODE)MAX9750/51 toc02
FREQUENCY (Hz)
THD+N (%)
VCC = 5V
RL = 4Ω
AV = 10.5dB
OUTPUT POWER = 1.25W
OUTPUT POWER = 500mW
0.00011k10k100100k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (SPEAKER MODE)MAX9750/51 toc03
FREQUENCY (Hz)
THD+N (%)
VCC = 5V
RL = 8Ω
AV = 10.5dB
OUTPUT POWER = 100mW
OUTPUT POWER = 600mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)
MAX9750/51 toc04
OUTPUT POWER (W)
THD+N (%)
VCC = 5V
RL = 3Ω
AV = 10.5dB
MAX9750C
fIN = 10kHz
fIN = 1kHzfIN = 20Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)MAX9750/51 toc05
OUTPUT POWER (W)
THD+N (%)
VDD = 5V
AV = 13.5dB
RL = 3Ω
f = 1kHz
f = 10kHz
f = 20Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)
MAX9750/51 toc06
OUTPUT POWER (W)
THD+N (%)
fIN = 1kHzfIN = 20Hz
VCC = 5V
RL = 4Ω
AV = 10.5dB
MAX9750C
fIN = 10kHz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)MAX9750/51 toc07
OUTPUT POWER (W)
THD+N (%)
VDD = 5V
AV = 13.5dB
RL = 4Ω
f = 1kHz
f = 10kHz
f = 20Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)
MAX9750/51 toc08
OUTPUT POWER (W)
THD+N (%)
fIN = 20HzfIN = 1kHz
fIN = 10kHz
VCC = 5V
RL = 8Ω
AV = 10.5dB
MAX9750C
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)MAX9750/51 toc09
OUTPUT POWER (W)
THD+N (%)
VDD = 5V
AV = 13.5dB
RL = 8Ω
f = 1kHzf = 10kHz
f = 20Hz
Typical Operating Characteristics (continued)(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
OUTPUT POWER
vs. LOAD RESISTANCE (SPEAKER MODE)MAX9750/51 toc10
LOAD RESISTANCE (Ω)
OUTPUT POWER (W)
THD+N = 10%
THD+N = 1%
OUTPUT POWER
vs. LOAD RESISTANCE (SPEAKER MODE)MAX9750/51 toc11
LOAD RESISTANCE (Ω)
OUTPUT POWER (W)
THD+N = 10%
THD+N = 1%
VCC = 5V
f = 1kHz
AV = 10.5dB
MAX9750C
POWER DISSIPATION vs. OUTPUT POWER
(SPEAKER MODE)MAX9750/51 toc12
OUTPUT POWER (W)
POWER DISSIPATION (W)21
RL = 4Ω
RL = 8Ω
VDD = 5V
f = 1kHz
POUT = POUTL + POUTR
POWER DISSIPATION vs. OUTPUT POWER
(SPEAKER MODE)MAX9750/51 toc13
OUTPUT POWER (W)
POWER DISSIPATION (W)
RL = 4Ω
RL = 8Ω
VDD = 5V
f = 1kHz
POUT = POUTL + POUTR
MAX9750C
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY (SPEAKER MODE)MAX9750/51 toc14
FREQUENCY (Hz)
PSRR (dB)
10k1k100
-100100k
VRIPPLE = 200mVP-P
AV = 10.5dB
OUTPUT REFERRED
-1201k10k100100k
CROSSTALK vs. FREQUENCY
(SPEAKER MODE)MAX9750/51 toc15
FREQUENCY (Hz)
CROSSTALK (dB)
VCC = 5V
VRIPPLE = 200mVP-P
RL = 4Ω
LEFT TO RIGHT
RIGHT TO LEFT
TURN-ON RESPONSE
(SPEAKER MODE)MAX9750/51 toc16
20ms/div
SHDN
5V/div
2V/div
100mV/div
OUT_+
AND
OUT_-
OUT_+
- OUT_-
RL = 8Ω
Typical Operating Characteristics (continued)(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers0.00011k10k100100k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)MAX9750/51 toc19
FREQUENCY (Hz)
THD+N (%)
VDD = 5V
RL = 32Ω
AV = 3dB
OUTPUT POWER = 45mW
OUTPUT POWER = 10mW
0.00011k10k100100k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)MAX9750/51 toc20
FREQUENCY (Hz)
THD+N (%)
VDD = 3.3V
RL = 16Ω
AV = 3dB
OUTPUT POWER = 30mW
OUTPUT POWER = 10mW
0.00011k10k100100k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)MAX9750/51 toc21
FREQUENCY (Hz)
THD+N (%)
VDD = 3.3V
RL = 32Ω
AV = 3dB
OUTPUT POWER = 45mW
OUTPUT POWER = 10mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
MAX9750/51 toc22
OUTPUT POWER (mW)
THD+N (%)
VDD = 5V
RL = 16Ω
AV = 3dB
fIN = 10kHz
fIN = 1kHzfIN = 20Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
MAX9750/51 toc23
OUTPUT POWER (mW)
THD+N (%)
VDD = 5V
RL = 32Ω
AV = 3dB
fIN = 10kHz
fIN = 1kHz
fIN = 20Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
MAX9750/51 toc24
OUTPUT POWER (mW)
THD+N (%)
VDD = 3.3V
RL = 16Ω
AV = 3dB
fIN = 10kHz
fIN = 1kHz
fIN = 20Hz
TURN-OFF RESPONSE
(SPEAKER MODE)MAX9750/51 toc17
20ms/div
SHDN
5V/div
2V/div
20mV/div
OUT_+
AND
OUT_-
OUT_+
- OUT_-
RL = 8Ω
0.00011k10k100100k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)MAX9750/51 toc18
FREQUENCY (Hz)
THD+N (%)
VDD = 5V
RL = 16Ω
AV = 3dB
OUTPUT POWER = 90mW
OUTPUT POWER = 30mW
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
OUTPUT POWER vs. SUPPLY VOLTAGE
(HEADPHONE MODE)MAX9750/51 toc28
SUPPLYVOLTAGE(V)
OUTPUT POWER (mW)
RL = 16Ω
RL = 32Ω
f = 1kHz1k10k100100k
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY (HEADPHONE MODE)MAX9750/51 toc29
FREQUENCY(Hz)
PSRR (dB)
VRIPPLE = 200mVP-P
AV = 10.5dB
OUTPUT REFERRED
-1001001k10k100k
CROSSTALK vs. FREQUENCY
(HEADPHONE MODE)MAX9750/51 toc30
CROSSTALK (dB)
VCC = 5V
VRIPPLE = 200mVP-P
RL = 32Ω
LEFT TO RIGHT
RIGHT TO LEFT
OUTPUT POWER vs. CHARGE-PUMP
CAPACITANCE AND LOAD RESISTANCE
MAX9750/51 toc31
OUTPUT POWER (mW)3020
VDD = 5V
f = 1kHz
THD+N = 1%
C1 = C2 = 2.2μF
C1 = C2 = 1μF
Typical Operating Characteristics (continued)(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
OUTPUT POWER vs. LOAD RESISTANCE
(HEADPHONE MODE)MAX9750/51 toc26
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
THD+N = 10%
THD+N = 1%
POWER DISSIPATION vs. OUTPUT POWER
(HEADPHONE MODE)MAX9750/51 toc27
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
VDD = 5V
f = 1kHz
POUT = POUTL + POUTR
RL = 16Ω
RL = 32Ω
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
MAX9750/51 toc25
OUTPUT POWER (mW)
THD+N (%)
VDD = 3.3V
RL = 32Ω
AV = 3dB
fIN = 10kHz
fIN = 1kHz
fIN = 20Hz
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
HEADPHONE OUTPUT SPECTRUMMAX9750/51 toc32
FREQUENCY (Hz)
MAGNITUDE (dB)105
VDD = 5V
f = 1kHz
VOUT = -60dB
RL = 32Ω
TURN-ON RESPONSE
(HEADPHONE MODE)MAX9750/51 toc33
10ms/div
SHDN
5V/div
20mV/divHPOUT_
RL = 32Ω
TURN-OFF RESPONSE
(HEADPHONE MODE)MAX9750/51 toc34
10ms/div
SHDN
5V/div
20mV/divHPOUT_
RL = 32Ω
SUPPLY CURRENT
vs. SUPPLY VOLTAGEMAX9750/51 toc35
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
HPS = GND
HPS = VDD
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGEMAX9750/51 toc36
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
Typical Operating Characteristics (continued)
(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Pin Description
PIN
MAX9750MAX9751MAX9755
NAMEFUNCTION—2INLLeft-Channel Audio Input——BEEPAudible Alert Beep Input
3, 193, 193, 19PGNDPower Ground. Connect PGND to GND at a single point on the PCB near
the device.44OUTL+Left-Channel Positive Speaker Output55OUTL-Left-Channel Negative Speaker Output
6, 166, 166, 16PVDDSpeaker Amplifier Power Supply77CPVDDCharge-Pump Power Supply88C1PCharge-Pump Flying-Capacitor Positive Terminal99CPGNDCharge-Pump Ground. Connect CPGND to PGND.1010C1NCharge-Pump Flying-Capacitor Negative Terminal1111CPVSSCharge-Pump Output. Connect to VSS.1212VSSHeadphone Amplifier Negative Power Supply1313HPOUTRRight-Channel Headphone Output1414HPOUTLLeft-Channel Headphone Output1515HPVDDHeadphone Positive Power Supply1717OUTR-Right-Channel Negative Speaker Output1818OUTR+Right-Channel Positive Speaker Output2020HPSHeadphone Sense Input2121BIASCommon-Mode Bias Voltage. Bypass with a 1µF capacitor to GND.2222SHDNShutdown. Drive SHDN low to disable the device. Connect SHDN to VDD
for normal operation.——GAIN2Gain Control Input 2——GAIN1Gain Control Input 12525VDDPower Supply2623, 26GNDGround. Connect GND to PGND at a single point on the PCB near the
device.—28INRRight-Channel Audio Input——VOLAnalog Volume Control Input1—INL1Left-Channel Audio Input 12—INL2Left-Channel Audio Input 223—IN1/2Input Select2424GAINGain Select27—INR1Right-Channel Audio Input 128—INR2Right-Channel Audio Input 2—1, 27N.C.No Connection. Not internally connected.—1, 27N.C.No Connection. Not internally connected.EPEPEPExposed Paddle. Connect to GND.
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Detailed DescriptionThe MAX9750/MAX9751/MAX9755 combine a 2.6W BTL
speaker amplifier and a 110mW DirectDrive headphone
amplifier with integrated headphone sensing and com-
prehensive click-and-pop suppression. The MAX9750
features an analog volume control, BEEP input, and
four-level gain control. The MAX9751 features a 2:1
input stereo multiplexer and two-level gain control. All
devices feature high 90dB PSRR, low 0.01% THD+N,
industry-leading click-pop performance, and a low-
power shutdown mode.
Each signal path consists of an input amplifier that sets
the gain of the signal path and feeds both the speaker
and headphone amplifier (Figure 1). The speaker
amplifier uses a BTL architecture, doubling the voltage
drive to the speakers and eliminating the need for DC-
blocking capacitors. The output consists of two signals,
identical in magnitude, but 180°out of phase.
The headphone amplifiers use Maxim’s DirectDrive
architecture that eliminates the bulky output DC-block-
ing capacitors required by traditional headphone ampli-
fiers. A charge pump inverts the positive supply
(CPVDD), creating a negative supply (CPVSS). The
headphone amplifiers operate from these bipolar sup-
plies with their outputs biased about GND (Figure 2).
The amplifiers have almost twice the supply range
compared to other single-supply amplifiers, nearly qua-
drupling the available output power. The benefit of the
GND bias is that the amplifier outputs no longer have a
DC component (typically VDD / 2). This eliminates the
large DC-blocking capacitors required with convention-
al headphone amplifiers, conserving board space and
system cost, and improving frequency response.
The MAX9750 features an analog volume control that
varies the gain of the amplifiers based on the DC volt-
age applied at VOL. Both devices feature an undervolt-
age lockout that prevents operation from an insufficient
power supply and click-and-pop suppression that elim-
inates audible transients on startup and shutdown. The
amplifiers include thermal-overload and short-circuit
protection, and can withstand ±8kV ESD strikes on the
headphone amplifier outputs (IEC air discharge). An
additional feature of the speaker amplifiers is that there
is no phase inversion from input to output.
DirectDriveConventional single-supply headphone amplifiers have
their outputs biased about a nominal DC voltage (typi-
cally half the supply) for maximum dynamic range.
Large coupling capacitors are needed to block this DC
bias from the headphones. Without these capacitors, a
OUT_+
OUT_VOLUME
CONTROLBIAS
IN_
VOL
BIAS
MAX9750 ONLY
BIAS
HPOUT_
GND
Figure 1. MAX9750/MAX9751 Signal Path
+VDD
-VDD
GND
CONVENTIONAL DRIVER-BIASING SCHEME
DirectDrive BIASING SCHEME
VDD/2
VDD
GND
VOUT
Figure 2. Traditional Headphone Amplifier Output Waveform
vs. DirectDrive Headphone Amplifier Output Waveform
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifierssignificant amount of DC current flows to the headphone,
resulting in unnecessary power dissipation and possible
damage to both headphone and headphone amplifier.
Maxim’s DirectDrive architecture uses a charge pump to
an internal negative supply voltage. This allows the
MAX9750/MAX9751/MAX9755 headphone amplifier out-
put to be biased about GND, almost doubling the dynam-
ic range while operating from a single supply. With no DC
component, there is no need for the large DC-blocking
capacitors. Instead of two large capacitors (220µF typ),
the MAX9750/MAX9751/MAX9755 charge pump requires
only two small ceramic capacitors (1µF typ), conserving
board space, reducing cost, and improving the frequen-
cy response of the headphone amplifier. See the Output
Power vs. Charge-Pump Capacitance and Load
Resistance graph in the Typical Operating
Characteristicsfor details of the possible capacitor val-
ues.
Previous attempts to eliminate the output coupling
capacitors involved biasing the headphone return
(sleeve) to the DC bias voltage of the headphone
amplifiers. This method raised some issues:The sleeve is typically grounded to the chassis. Using
this biasing approach, the sleeve must be isolated
from system ground, complicating product design.During an ESD strike, the amplifier’s ESD structures
are the only path to system ground. The amplifier
must be able to withstand the full ESD strike.When using the headphone jack as a lineout to other
equipment, the bias voltage on the sleeve may con-
flict with the ground potential from other equipment,
resulting in large ground-loop current and possible
damage to the amplifiers.
Low-Frequency ResponseIn addition to the cost and size disadvantages, the DC-
blocking capacitors limit the low-frequency response of
the amplifier and distort the audio signal:The impedance of the headphone load to the DC-
blocking capacitor forms a highpass filter with the
-3dB point determined by:
where RLis the impedance of the headphone and
COUTis the value of the DC-blocking capacitor.
The highpass filter is required by conventional sin-
gle-ended, single-supply headphone amplifiers to
block the midrail DC component of the audio signal
from the headphones. Depending on the -3dB point,
the filter can attenuate low-frequency signals within
the audio band. Larger values of COUTreduce the
attenuation but are physically larger, more expen-
sive capacitors. Figure 3 shows the relationship
between the size of COUTand the resulting low-fre-
quency attenuation. Note that the -3dB point for a
16Ωheadphone with a 100µF blocking capacitor is
100Hz, well within the audio band.The voltage coefficient of the capacitor, the change
in capacitance due to a change in the voltage
across the capacitor, distorts the audio signal. At
frequencies around the -3dB point, the reactance of
the capacitor dominates, and the voltage coefficient
appears as frequency-dependent distortion. Figure
4 shows the THD+N introduced by two different
capacitor dielectrics. Note that around the -3dB
point, THD+N increases dramatically.
The combination of low-frequency attenuation and fre-
quency-dependent distortion compromises audio
reproduction. DirectDrive improves low-frequency
reproduction in portable audio equipment that empha-
sizes low-frequency effects such as multimedia lap-
tops, and MP3, CD, and DVD players.
Charge PumpThe MAX9750/MAX9751/MAX9755 feature a low-noise
charge pump. The 550kHz switching frequency is well
beyond the audio range, and does not interfere with the
audio signals. The switch drivers feature a controlled
switching speed that minimizes noise generated by turn-
on and turn-off transients. Limiting the switching speed of
the charge pump minimizes the di/dt noise caused by theRCdBLOUT−=31
-301001k10k100k
LOW-FREQUENCY ROLLOFF
(RL = 16Ω)FREQUENCY (Hz)
ATTENUATION (dB)
DirectDrive
330μF
220μF
100μF
33μF
Figure 3. Low-Frequency Attenuation of Common DC-Blocking
Capacitor Values
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiersparasitic bond wire and trace inductance. Although not
typically required, additional high-frequency ripple atten-
uation can be achieved by increasing the size of C2 (see
the Block Diagrams).
Headphone Sense Input (HPS)The headphone sense input (HPS) monitors the head-
phone jack and automatically configures the device
based upon the voltage applied at HPS. A voltage of
less than 0.8V sets the device to speaker mode. A volt-
age of greater than 2V disables the bridge amplifiers
and enables the headphone amplifiers.
For automatic headphone detection, connect HPS to the
control pin of a 3-wire headphone jack as shown in
Figure 5. With no headphone present, the output imped-
ance of the headphone amplifier pulls HPS low. When a
headphone plug is inserted into the jack, the control pin
is disconnected from the tip contact and HPS is pulled
to VDDthrough a 10µA current source.
BIASThe MAX9750/MAX9751/MAX9755 feature an internally
generated, power-supply independent, common-mode
bias voltage of 1.8V referenced to GND. BIAS provides
both click-and-pop suppression and sets the DC bias
level for the amplifiers. Choose the value of the bypass
capacitor as described in the BIAS Capacitorsection.
No external load should be applied to BIAS. Any load
lowers the BIAS voltage, affecting the overall perfor-
mance of the device.
Gain Selection
MAX9750The MAX9750 features an internally set, selectable gain.
The GAIN1 and GAIN2 inputs set the maximum gain of
the MAX9750 speaker and headphone amplifiers (Table
1). The gain of the device can vary based upon the volt-
age at VOL (see the Analog Volume Control (VOL)sec-
tion). However, the maximum gain cannot be exceeded.
MAX9751/MAX9755The gain of the MAX9751/MAX9755 is set by the GAIN
input. Driving GAIN high sets the gain of the speaker
amplifiers to 9dB and the gain of the headphone ampli-
fiers to 0dB. Driving GAIN low sets the gain of the
speaker amplifiers to 10.5dB, and the gain of the head-
phone amplifiers to 3dB (Table 2).
Analog Volume Control (VOL)The MAX9750 features an analog volume control that
varies the gain of the device in 31 discrete steps based
upon the DC voltage applied to VOL. The input range of
VVOLis from 0 (full volume) to 0.858 x HPVDD(full mute),
with example step sizes shown in Table 3. Connect the
reference of the device driving VOL (Figure 6) to HPVDD.
Since the volume control ADC is ratiometric to HPVDD,
any changes in HPVDDare negated. The gain step sizes
are not constant; the step sizes are 0.5dB/step at the
upper extreme, 2dB/step in the midrange, and 4dB/step
at the lower extreme. Figure 7 shows the transfer function
of the volume control for a 3.3V supply.
ADDITIONAL THD+N DUE
TO DC-BLOCKING CAPACITORSFREQUENCY (Hz)
THD+N (%)
10k1k100
0.0001100k
TANTALUM
ALUM/ELEC
Figure 4. Distortion Contributed by DC-Blocking Capacitors
MAX9750/
MAX9751/
MAX9755 10μA
1kΩ1kΩ
VDD
HPS
HPOUTL
HPOUTR
SHUTDOWN
CONTROL
Figure 5. HPS Configuration
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
BEEP InputThe MAX9750 features an audible alert beep input
(BEEP) that accepts a mono system alert signal and
mixes it into the stereo audio path. When the amplitude
of VBEEP(OUT)exceeds 800mVP-P(Figure 8) and the
frequency of the beep signal is greater than 300Hz, the
beep signal is mixed into the active audio path (speaker
or headphone). If the signal at VBEEP(OUT)is either
< 800mVP-Por < 300Hz, the BEEP signal is not mixed
into the audio path. The amplitude of the BEEP signal at
the device output is roughly the amplitude of VBEEP(OUT)
times the gain of the selected signal path.
The input resistor (RB) sets the gain of the BEEP input
amplifier, and thus the amplitude of VBEEP(OUT). Choosebased on:
where RINTis the value of the BEEP amplifier feedback
resistor (47kΩ) and VINis the BEEP input amplitude.
Note that the BEEP amplifier can be set up as either an
attenuator, if the original alert signal amplitude is too
large, or set to gain up the alert signal if it is below
800mVP-P. AC couple the alert signal to BEEP. Choose
the value of the coupling capacitor as described in the
Input Filteringsection. Multiple beep inputs can be
summed (Figure 8).
Input MultiplexerThe MAX9751 features a 2:1 input multiplexer on each
amplifier, allowing input selection between two stereo
sources. The logic input IN1/2controls both multiplex-
ers. A logic high selects input IN_1 and a logic low
selects input IN_2.
ShutdownThe MAX9750/MAX9751/MAX9755 features a 0.2µA,
low-power shutdown mode that reduces quiescent cur-
rent consumption and extends battery life. Driving
SHDNlow disables the drive amplifiers, bias circuitry,
and charge pump, and drives BIAS and all outputs to
GND. Connect SHDNto VDDfor normal operation.
Click-and-Pop Suppression
Speaker AmplifierThe MAX9750/MAX9751/MAX9755 speaker amplifiers
feature Maxim’s comprehensive, industry-leading click-
and-pop suppression. During startup, the click-pop
suppression circuitry eliminates any audible transient
sources internal to the device. When entering shut-
down, both amplifier outputs ramp to GND quickly and
simultaneously.VRININT ≤×
MAX9750
VREF
DAC
HPVDD
VOL
Figure 6. Volume Control Circuit
GAINSPEAKER MODE
GAIN (dB)
HEADPHONE
MODE GAIN (dB)10.530
Table 2. MAX9751/MAX9755 Gain Settings
SPEAKER MODE GAIN (dB)GAIN2GAIN1
MAX9750AMAX9750BMAX9750C
HEADPHONE MODE GAIN (dB)091560110.516.57.500121893113.519.510.53
Table 1. MAX9750 Maximum Gain Settings
