MAX9723AETE+-MAX9723DEBE+T-MAX9723DETE+-MAX9723DETE+T-MAX9723DETE+TCJ6 Fast Delivery |IC PHOENIX CO.,LIMITED

MAX9723DETE+T ,Stereo DirectDrive® Headphone Amplifier with BassMax, Volume Control, and I²Cfeatures Maxim’s industry-leading 2● I C/SMBus-Compatible Interfaceclick-and-pop suppression.● Avai ..
MAX9723DETE+TCJ6 ,Stereo DirectDrive® Headphone Amplifier with BassMax, Volume Control, and I²CFeatures®● 62mW, DirectDrive Headphone Amplifier Eliminates The MAX9723 stereo DirectDrive headphon ..
MAX9724AEBC+T ,60mW, DirectDrive, Stereo Headphone Amplifier with Low RF Susceptibility and ShutdownFeaturesThe MAX9724A/MAX9724B stereo headphone ampli- ♦ Improved RF Noise Rejection (Up to 67dB Ove ..
MAX9724AEBC+TG45 ,60mW, DirectDrive, Stereo Headphone Amplifier with Low RF Susceptibility and ShutdownFeaturesThe MAX9724A/MAX9724B stereo headphone ampli- ♦ Improved RF Noise Rejection (Up to 67dB Ove ..
MAX9724AETC+ ,60mW, DirectDrive, Stereo Headphone Amplifier with Low RF Susceptibility and ShutdownELECTRICAL CHARACTERISTICS(V = 5V, PGND = SGND, SHDN = 5V, C1 = C2 = 1µF, R = ∞, resistive load ref ..
MAX9724AETC+T ,60mW, DirectDrive, Stereo Headphone Amplifier with Low RF Susceptibility and ShutdownApplications+Denotes lead(Pb)-free/RoHS-compliant package.DVD PlayersCellular Phones T = Tape and r ..
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MB89537AC , 8-bit Original Microcontroller CMOS, F-2MC-8L MB89530A Series

MAX9723AETE+-MAX9723DEBE+T-MAX9723DETE+-MAX9723DETE+T-MAX9723DETE+TCJ6
Stereo DirectDrive® Headphone Amplifier with BassMax, Volume Control, and I²C
General Description
The MAX9723 stereo DirectDrive® headphone amplifier
with BassMax and volume control is ideal for portable
audio applications where space is at a premium and
performance is essential. The MAX9723 operates from a
single 1.8V to 3.6V power supply and includes features
that reduce external component count, system cost,
board space, and improves audio reproduction.
The headphone amplifier uses Maxim’s DirectDrive archi-
tecture that produces a ground-referenced output from a
single supply, eliminating the need for large DCblocking
capacitors. The headphone amplifiers deliver 62mW into a 16Ω load, feature low 0.006% THD+N, and high 90dB
PSRR. The MAX9723 features Maxim’s industry-leading
click-and-pop suppression.
The BassMax feature boosts the bass response of
the amplifier, improving audio reproduction when using
inexpensive headphones. The integrated volume control
features 32 discrete volume levels, eliminating the need
for an external potentiometer. BassMax and the volume
control are enabled through the I2C/SMBus™-compatible
interface. Shutdown is controlled through either the hard-
ware or software interfaces.
The MAX9723 consumes only 3.7mA of supply current at
1.8V, provides short-circuit and thermal-overload protection, and is fully specified over the extended -40°C to +85°C tem-
perature range. The MAX9723 is available in a tiny (2mm x 2mm x 0.62mm) 16-bump chip-scale package (UCSP™) or 16-pin thin QFN (4mm x 4mm x 0.8mm) package.
Applications
Features●62mW, DirectDrive Headphone Amplifier Eliminates
Bulky DC-Blocking Capacitors●1.8V to 3.6V Single-Supply Operation●Integrated 32-Level Volume Control●High 90dB PSRR at 1kHz●Low 0.006% THD+N●Industry-Leading Click-and-Pop Suppression●±8kV HBM ESD-Protected Headphone Outputs●Short-Circuit and Thermal-Overload Protection●Low-Power Shutdown Mode (5μA)●Software-Enabled Bass Boost (BassMax)●I2C/SMBus-Compatible Interface●Available in Space-Saving, Thermally Efficient
Packages: • 16-Bump UCSP (2mm x 2mm x 0.62mm) • 16-Pin Thin QFN (4mm x 4mm x 0.8mm)
Pin Configurations appears at end of data sheet.●PDA Audio●Portable CD Players●Mini Disc Players ●MP3-Enabled Cellular●Phones●MP3 Players
**Replace the ‘_’ with the one-letter code that denotes the slave
address and maximum programmable gain. See the Selector
Guide.+Denotes a lead-free/RoHS-compliant package.
*Future product—contact factory for availability.
DirectDrive is a registered trademark of Maxim Integrated
Products, Inc.
SMBus is a trademark of Intel Corp.
UCSP is a trademark of Maxim Integrated Products, Inc.
PARTSLAVE ADDRESSMAXIMUM GAIN (dB)
MAX9723A10011000
MAX9723B10011010
MAX9723C1001100+6
MAX9723D1001101+6
PART**TEMP RANGEPIN-
PACKAGE
PKG
CODE
MAX9723_EBE-T*-40°C to +85°C16 UCSP-16B16-1
MAX9723_ETE+-40°C to +85°C16 TQFNT1644-4
I2C INTERFACE
VOLUME
CONTROL
BassMax
BassMax
1.8V TO 3.6V SUPPLY
SCL
BBL
OUTL
BBR
OUTR
SDA
INL
INR
MAX9723
MAX9723Stereo DirectDrive Headphone Amplifier
with BassMax, Volume Control, and I2C
Block Diagram
Ordering Information
Selector Guide
EVALUATION KIT AVAILABLE
SGND to PGND .....................................................-0.3V to +0.3V
VDD to PGND...........................................................-0.3V to +4V
PVSS to SVSS.......................................................-0.3V to +0.3VC1P to PGND.............................................-0.3V to (VDD + 0.3V)C1N to PGND...........................................(PVSS - 0.3V) to +0.3V
PVSS, SVSS to PGND..............................................+0.3V to -4VIN_ to SGND.................................(SVSS - 0.3V) to (VDD + 0.3V)SDA, SCL to PGND..................................................-0.3V to +4V
SHDN to PGND..........................................-0.3V to (VDD + 0.3V)OUT_ to SGND............................................................-3V to +3VBB_ to SGND...............................................................-2V to +2VDuration of OUT_ Short Circuit to _GND ....................Continuous
Continuous Current Into/Out of:
VDD, C1P, PGND, C1N, PVSS, SVSS, or OUT_...........±0.85A Any Other Pin................................................................±20mA
Continuous Power Dissipation (TA = +70°C) 4 x 4 UCSP (derate 8.2mW/°C above +70°C)..........659.2mW 16-Pin Thin QFN (derate 16.9mW/°C above +70°C)....1349mWOperating Temperature Range.............................-40°C to +85°C
Junction Temperature.......................................................+150°CStorage Temperature Range .............................-65°C to +150°CBump Temperature (soldering) Reflow ..........................................................................+230°CLead Temperature (soldering, 10s) .................................+300°C
(VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1μF, BB_ = 0V. gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where specified. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
GENERAL
Supply Voltage RangeVDD1.83.6V
Quiescent Supply CurrentIDDNo load46.5mA
Shutdown Supply CurrentIDD_SHDNVSHDN = 0V58.5µA
Turn-On TimetON200µs
Turn-Off TimetOFF35µs
Thermal Shutdown ThresholdTTHRES+143°C
Thermal Shutdown HysteresisTHYST12°C
HEADPHONE AMPLIFIER
Output Offset VoltageVOS
Measured between OUT_ and SGND (Note 2)
Gain = 0dB,
MAX9723A/
MAX9723B±0.7±4.5Gain = +6dB,
MAX9723C/
MAX9723D±0.8±5
Input ResistanceRINAll volume levels101727kΩ
BBR, BBL Input Bias CurrentIBIAS_BB±10±100nA
Power-Supply Rejection RatioPSRR(Note 2)
DC, VDD = 1.8V to 3.6V7390
f = 217Hz, 100mVP-P ripple,
VDD = 3.0V87
f = 1kHz, 100mVP-P ripple,
VDD = 3.0V86
f = 20kHz, 100mVP-P ripple,
VDD = 3.0V61
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Electrical Characteristics
(VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1μF, BB_ = 0V. gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where specified. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Output PowerPOUTTHD+N = 1%,
fIN = 1kHz
RL = 32Ω59mW
RL = 16Ω (Note 5)3860
Total Harmonic Distortion Plus NoiseTHD+NRL = 16Ω, POUT = 35mW, fIN = 1kHz0.006%RL = 32Ω, POUT = 45mW, fIN = 1kHz0.004
Maximum GainAMAX
MAX9723A/
MAX9723B
Gain range bit 5 = 10dBGain range bit 5 = 0-5
MAX9723C/
MAX9723D
Gain range bit 5 = 1+6dBGain range bit 5 = 0+1
Signal-to-Noise RatioSNRRL = 32Ω,
VOUT = 1VRMS
BW = 22Hz to 22kHz99A-weighted100
Slew RateSR0.35V/µs
Capacitive DriveNo sustained oscillations300pF
Output Resistance in ShutdownROUT_SHDNVSHDN = 0V, measured from OUT_ to SGND20kΩ
Output Capacitance in ShutdownCOUT_SHDNVSHDN = 0V, measured from OUT_ to SGND60pF
Click/Pop LevelKCP
RL = 32Ω,
peak voltage,
A-weighted,
32 samples
per second (Notes 2, 4)
MAX9723A/
MAX9723B
Into
shutdown-69
Out of
shutdown-71
MAX9723C/
MAX9723D
Into
shutdown-70
Out of
shutdown-69
Charge-Pump Switching
FrequencyfCP505600700kHz
CrosstalkXTALKL to ≥ or ≥ to L, f = 10kHz,
VOUT = 1VP-P, RL = 32Ω, both channels
loaded80dB
DIGITAL INPUTS (SHDN, SDA, SCL)
Input High VoltageVIH0.7 x
VDDV
Input Low VoltageVIL0.3 x
VDDV
Input Leakage CurrentP1µA
DIGITAL OUTPUTS (SDA)
Output Low VoltageVOLIOL = 3mA0.4V
Output High CurrentIOHVSDA = VDD1µA
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
Electrical Characteristics (continued)
(VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1μF, BB_ = 0V. gain = 0dB, maximum volume, BassMax disabled. Load con-nected between OUT_ and SGND where specified. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C, see Timing Diagram.) (Notes 1, 3)
Note 1: All specifications are 100% tested at TA = +25°C. Temperature limits are guaranteed by design.
Note 2: Inputs AC-coupled to SGND.
Note 3: Guaranteed by design.
Note 4: Headphone mode testing performed with a 32Ω resistive load connected to GND. Mode transitions are controlled by SHDN. The KCP level is calculated as: 20 x log [(level peak voltage during mode transition, no input signal)/(peak voltage under normal operation at rated power)]. Units are expressed in dB.
Note 5: Output power MIN is specified at TA = +25°C.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Serial Clock FrequencyfSCL0400kHz
Bus Free Time Between a STOP
and a START ConditiontBUF1.3µs
START Condition Hold TimetHD:STA0.6µs
Low Period of the SCL ClocktLOW1.3µs
High Period of the SCL ClocktHIGH0.6µs
Setup Time for a Repeated
START ConditiontSU:STA0.6µs
Data Hold TimetHD:DAT00.9µs
Data Setup TimetSU:DAT100ns
Maximum Rise Time of SDA and
SCL Signalstr300ns
Maximum Fall Time of SDA and
SCL Signalstf300ns
Setup Time for STOP ConditiontSU:STO0.6µs
Pulse Width of Suppressed SpiketSP100ns
Maximum Capacitive Load for Each Bus LineCL_BUS400pF
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
Timing Characteristics
(VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1μF, BB_ = 0V, gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where speciied. Outputs in phase, both channels loaded. TA = +25°C, unless otherwise noted.) (See Func-
tional Diagram/Typical Operating Circuit)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
MAX9723 toc02
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.001100k
VDD = 2.4V
RL = 32Ω
POUT = 23mW
POUT = 10mW
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
MAX9723 toc03
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.001100k
VDD = 3V
RL = 16Ω
POUT = 37mW
POUT = 20mW
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
MAX9723 toc04
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.001100k
VDD = 3V
RL = 32Ω
POUT = 30mW
POUT = 10mW
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
MAX9723 toc05
OUTPUT POWER (mW)
THD+N (%)20
VDD = 2.4V
RL = 16Ω
fIN = 1kHzfIN = 20HzfIN = 10kHz
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
MAX9723 toc06
OUTPUT POWER (mW)
THD+N (%)20
VDD = 2.4V
RL = 32Ω
fIN = 1kHz
fIN = 10kHzfIN = 20Hz
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
MAX9723 toc07
THD+N (%)604020
VDD = 3V
RL = 16Ω
fIN = 10kHzfIN = 1kHz
fIN = 20Hz
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
MAX9723 toc01
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.001100k
VDD = 2.4V
RL = 16Ω
POUT = 10mW
POUT = 25mW
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
MAX9723 toc08
THD+N (%)604020
VDD = 3V
RL = 32Ω
fIN = 10kHz
fIN = 1kHz
fIN = 20Hz
POWER DISSIPATION
vs. OUTPUT POWER
MAX9723 toc09
POWER DISSIPATION (mW)
VDD = 2.4V
fIN = 1kHz
POUT = POUTL + POUTR
OUTPUTS IN PHASE
RL = 32Ω
RL = 16Ω
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
Typical Operating Characteristics
(VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1μF, BB_ = 0V, gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where speciied. Outputs in phase, both channels loaded. TA = +25°C, unless otherwise noted.) (See Func-
tional Diagram/Typical Operating Circuit)
POWER DISSIPATION
vs. OUTPUT POWER
MAX9723 toc10
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
RL = 16Ω
VDD = 3V
fIN = 1kHz
POUT = POUTL + POUTR
OUTPUTS IN PHASE
RL = 32Ω
OUTPUT POWER
vs. LOAD RESISTANCE
MAX9723 toc11
LOAD RESISTANCE (W)
OUTPUT POWER (mW)
1001k
VDD = 2.4V
fIN = 1kHz
THD+N = 10%
THD+N = 1%
OUTPUT POWER
vs. LOAD RESISTANCE
MAX9723 toc12
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
1001k
VDD = 3V
fIN = 1kHz
THD+N = 10%
THD+N = 1%
OUTPUT POWER
vs. SUPPLY VOLTAGE
MAX9723 toc13
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
THD+N = 10%
THD+N = 1%
fIN = 1kHz
RL = 16Ω
OUTPUT POWER
vs. SUPPLY VOLTAGE
MAX9723 toc14
OUTPUT POWER (mW)
THD+N = 10%
THD+N = 1%
fIN = 1kHz
RL = 32Ω
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX9723 toc15
PSRR (dB)
10k1k100
-100100k
RL = 32Ω
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
Typical Operating Characteristics (continued)
(VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1μF, BB_ = 0V, gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where speciied. Outputs in phase, both channels loaded. TA = +25°C, unless otherwise noted.) (See Func-
tional Diagram/Typical Operating Circuit)
CROSSTALK
vs. FREQUENCY
MAX9723 toc16
FREQUENCY (Hz)
CROSSTALK (dB)
10k1k10010100k
VIN = 1VP-P
RL = 32Ω
A = 0dB
LEFT TO RIGHT
A = 0dB
RIGHT TO LEFT
A = 0dB
CROSSTALK
vs. FREQUENCY
MAX9723 toc17
FREQUENCY (Hz)
CROSSTALK (dB)
10k1k10010100k
VIN = 1VP-P
RL = 32Ω
A = -10dB
LEFT TO RIGHT
A = -10dB
RIGHT TO LEFT
A = -10dB
BASS BOOST FREQUENCY
RESPONSE
MAX9723 toc18
FREQUENCY (Hz)
AMPLITUDE (dB)
10k1k10010100k
NO LOAD
R1 = 47kΩ
BassMax DISABLED
R2 = 36kΩ
C3 = 0.068µF
R2 = 22kΩ
C3 = 0.1µF
R2 = 10kΩ
C3 = 0.22µF
GAIN FLATNESS
vs. FREQUENCY
MAX9723 toc19
FREQUENCY (Hz)
AMPLITUDE (dB)
10k1k10010100k
OUTPUT SPECTRUM
vs. FREQUENCY
MAX9723 toc20
AMPLITUDE (dBV)105
RL = 32Ω
VDD = 3V
fIN = 1kHz
CHARGE-PUMP OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX9723 toc21
OUTPUT VOLTAGE (V)
NO HEADPHONE LOAD
CHARGE-PUMP LOAD
CONNECTED
BETWEEN PVSS AND PGND
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
Typical Operating Characteristics (continued)
(VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1μF, BB_ = 0V, gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where speciied. Outputs in phase, both channels loaded. TA = +25°C, unless otherwise noted.) (See Func-
tional Diagram/Typical Operating Circuit)
OUTPUT POWER vs. CHARGE-PUMP
CAPACITANCE AND LOAD RESISTANCE
MAX9723 toc22
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)302050
C1 = C2 = 2.2µF
C1 = C2 = 0.68µF
C1 = C2 = 1µF
VDD = 3V
fIN = 1kHz
THD+N = 1%
POWER-UP/POWER-DOWN
WAVEFORM
MAX9723 toc23
20ms/div
VDD
2V/div
VOUT
10mV/div
EXITING SHUTDOWN
MAX9723 toc24
40µs/div
VOUT_
200mV/div
VSHDN
2V/div
ENTERING SHUTDOWN
MAX9723 toc25
20µs/div
VOUT_
200mV/div
VSHDN
2V/div
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX9723 toc26
SUPPLY CURRENT (mA)
NO LOAD
INPUTS GROUNDED
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
SHUTDOWN CURRENT (µA)
MAX9723 toc27
NO LOAD
INPUTS GROUNDED
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
Typical Operating Characteristics (continued)
Detailed Description
The MAX9723 stereo headphone amplifier features
Maxim’s DirectDrive architecture, eliminating the large
output-coupling capacitors required by conventional sin-
gle-supply headphone amplifiers. The MAX9723 consists
of two 62mW Class AB headphone amplifiers, hardware/
software shutdown control, inverting charge pump, inte-
grated 32-level volume control, BassMax circuitry, com-
prehensive click-and-pop suppression circuitry, and an
I2C-compatible interface (see the Functional Diagram/
Typical Operating Circuit). A negative power supply
(PVSS) is created internally by inverting the positive sup-
ply (VDD). Powering the amplifiers from VDD and PVSS
increases the dynamic range of the amplifiers to almost
twice that of other single-supply amplifiers, increasing the
total available output power.
The MAX9723 DirectDrive outputs are biased at SGND (see Figure 1). The benefit of this 0V bias is that the ampli-
fier outputs do not have a DC component, eliminating the need for large DC-blocking capacitors. Eliminating the
DC-blocking capacitors on the output saves board space,
system cost, and improves low-frequency response.
An I2C-compatible interface allows serial communica-
tion between the MAX9723 and a microcontroller. The
MAX9723 is available with two different I2C addresses
allowing two MAX9723 ICs to share the same bus (see Table 1). The internal command register controls the
shutdown status of the MAX9723, enables the BassMax
circuitry, sets the maximum gain of the amplifier, and sets the volume level (see Table 2). The MAX9723’s BassMax
circuitry improves audio reproduction by boosting the
bass response of the amplifier, compensating for any low-
frequency attenuation introduced by the headphone. The
PINBUMPNAMEFUNCTION
THIN QFNUCSPD1VDDPower-Supply Input. Bypass VDD to PGND with a 1µF capacitor.C1C1PCharge-Pump Flying Capacitor Positive TerminalB1PGNDPower Ground. Connect to SGND.A1C1NCharge-Pump Flying Capacitor Negative TerminalB2SCLSerial Clock Input. Connect a 10kI pullup resistor from SCL to VDD.A2PVSSCharge-Pump Output. Connect to SVSS. Bypass PVSS with a 1µF capacitor to PGND.A3SDASerial-Data Input. Connect a 10kΩ pullup resistor from SDA to VDD.B3SHDNShutdown. Drive SHDN low to disable the MAX9723. Connect SHDN to VDD while bit 7
is high for normal operation (see the Command Register section).A4SGNDSignal Ground. Connect to PGND.B4INLLeft-Channel InputC4INRRight-Channel InputD4SVSSHeadphone Ampliier Negative Power-Supply Input. Connect to PVSS.C3BBRRight BassMax Input. Connect an external lowpass ilter between OUTR and BBR to apply bass boost to the right-channel output. Connect BBR to SGND if BassMax is not
used (see the BassMax (Bass Boost) section).D3OUTRRight Headphone OutputD2OUTLLeft Headphone OutputC2BBLLeft BassMax Input. Connect an external lowpass ilter between OUTL and BBL to apply bass boost to the left-channel output. Connect BBL to SGND if BassMax is not
used (see the BassMax (Bass Boost) section).—EPExposed Paddle. Connect EP to SVSS or leave unconnected.
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
Pin Description
MAX9723A and MAX9723B have a maximum amplifier gain of 0dB while the MAX9723C and MAX9723D have a maximum gain of +6dB. Amplifier volume is digitally
programmable to any one of 32 levels.
DirectDrive
Traditional single-supply headphone amplifiers have their
outputs biased at a nominal DC voltage, typically half
the supply, for maximum dynamic range. Large cou-
pling capacitors are needed to block this DC bias from
the headphone. Without these capacitors, a significant
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
create an internal negative supply voltage. This allows
the MAX9723 headphone amplifier outputs to be biased at 0V, almost doubling the dynamic range while operat-
ing from a single supply. With no DC component, there
is no need for the large DC-blocking capacitors. Instead of two large (typically 220μF) tantalum capacitors, the MAX9723 charge pump requires only two small 1μF
ceramic capacitors, thereby conserving board space,
reducing cost, and improving the low-frequency response
of the headphone amplifier. See the Output Power vs.
Charge-Pump Capacitance and Load Resistance graph
in the Typical Operating Characteristics for details of the possible capacitor sizes.
In addition to the cost and size disadvantages, the
phone amplifiers limit low-frequency response and can
distort the audio signal.
Previous attempts at eliminating the output-coupling capacitors involved biasing the headphone return (sleeve)
to the DC bias voltage of the headphone amplifiers. This
method raises some issues:
1) The sleeve is typically grounded to the chassis. Using
the midrail biasing approach, the sleeve must be
isolated from system ground, complicating product
design. The DirectDrive output biasing scheme allows
the sleeve to be grounded.
2) During an ESD strike, the amplifier’s ESD structure is
the only path to system ground. The amplifier must be able to withstand the full ESD strike. The MAX9723 headphone outputs can withstand an ±8kV ESD strike (HBM).
3) When using the headphone jack as a line out to other
equipment, the bias voltage on the sleeve may con-
flict with the ground potential from other equipment,
resulting in possible damage to the amplifiers. The
DirectDrive outputs of the MAX9723 can be directly
coupled to other ground-biased equipment.
Charge Pump
The MAX9723 features a low-noise charge pump. The 600kHz switching frequency is well beyond the audio
range, and does not interfere with the audio signals. This enables the MAX9723 to achieve a 99dB SNR.
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 di/dt noise caused by the parasitic
bond wire and trace inductance. Although not typically
required, additional high-frequency noise attenuation can be achieved by increasing the size of C2 (see the
Functional Diagram/Typical Operating Circuit).
Shutdown
The MAX9723 features a 5μA, low-power shutdown mode
that reduces quiescent current consumption and extends
battery life. Shutdown is controlled by a hardware or
software interface. Driving SHDN low disables the drive
amplifiers, bias circuitry, charge pump, and sets the headphone amplifier output impedance to 20kΩ. Similarly, the MAX9723 enters shutdown when bit seven (B7) in
the control register is reset. SHDN and B7 must be high
to enable the MAX9723. The I2C interface is active and
the contents of the command register are not affected
when in shutdown. This allows the master to write to the
Figure 1. Traditional Amplifier Output vs. MAX9723 DirectDrive
Output
VDD
+VDD
-VDD
VDD/2
GND
SGND
CONVENTIONAL AMPLIFIER BIASING SCHEME
DirectDrive BIASING SCHEME
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
Click-and-Pop Suppression
The output-coupling capacitor is a major contributor of
audible clicks and pops in conventional single-supply
headphone amplifiers. The amplifier charges the coupling
capacitor to its output bias voltage at startup. During shut-
down the capacitor is discharged. This charging and dis-
charging results in a DC shift across the capacitor, which
appears as an audible transient at the speaker. Since the
MAX9723 headphone amplifier does not require output-
coupling capacitors, no audible transients occur.
Additionally, the MAX9723 features extensive click-and-
pop suppression that eliminates any audible transient sources internal to the device. The Power-Up/Power-
Down Waveform in the Typical Operating Characteristics
shows that there are minimal transients at the output upon
startup or shutdown.
In most applications, the preamplifier driving the MAX9723
has a DC bias of typically half the supply. The input-coupling
capacitor is charged to the preamplifier’s bias voltage
through the MAX9723’s input impedance (RIN) during start-
up. The resulting voltage shift across the capacitor creates
an audible click/pop. To avoid clicks/pops caused by the
input filter, delay the rise of SHDN by at least 4 time con-
stants, 4 x RIN x CIN, relative to the start of the preamplifier.
BassMax (Bass Boost)
Typical headphones do not have a flat-frequency response. The small physical size of the diaphragm does not allow the
headphone speaker to efficiently reproduce low frequen-
cies. This physical limitation results in attenuated bass
response. The MAX9723 includes a bass boost feature
that compensates for the headphone’s poor bass response
by increasing the amplifier gain at low frequencies.
The DirectDrive output of the MAX9723 has more head-
room than typical single-supply headphone amplifiers.
This additional headroom allows boosting the bass fre-
quencies without the output-signal clipping.
Program the BassMax gain and cutoff frequency with external components connected between OUT_ and BB_
(see the Functional Diagram/Typical Operating Circuit). Use the I2C-compatible interface to program the com-
mand register to enable/disable the BassMax circuit.
BB_ is connected to the noninverting input of the output
amplifier when BassMax is enabled. BB_ is pulled to SGND when BassMax is disabled. The typical application
of the BassMax circuit involves feeding a lowpass version of the output signal back to the amplifier. This is realized
using positive feedback from OUT_ to BB_. Figure 2
shows the connections needed to implement BassMax.
Maximum Gain Control
The MAX9723A and MAX9723B have selectable maxi-mum gains of -5dB or 0dB (see Table 5) while the
MAX9723C and MAX9723D have selectable maximum gains of +1dB or +6dB (see Table 6). Bit 5 in the command
register selects between the two maximum gain settings.
Volume Control
The MAX9723 includes a 32-level volume control that
adjusts the gain of the output amplifiers according to
the code contained in the command register. Volume is programmed through the command register bits [4:0]. Tables 7–10 show all of the available gain settings for the
MAX9723A–MAX9723D. The mute attenuation is typically better than 100dB when driving a 32Ω load.
Serial Interface
The MAX9723 features an I2C/SMBus-compatible, 2-wire serial interface consisting of a serial data line (SDA) and a serial clock line (SCL). SDA and SCL facilitate commu-
nication between the MAX9723 and the master at clock rates up to 400kHz. Figure 3 shows the 2-wire interface
timing diagram. The MAX9723 is a receive-only slave
device relying on the master to generate the SCL signal.
The MAX9723 cannot write to the SDA bus except to
acknowledge the receipt of data from the master. The
Figure 2. BassMax External ConnectionsR2
OUT_
BB_
AUDIO
INPUT
BassMax
ENABLE
MAX9723
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
master, typically a microcontroller, generates SCL and
initiates data transfer on the bus.
A master device communicates to the MAX9723 by trans-
mitting the proper address followed by the data word. Each transmit sequence is framed by a START (S) or REPEATED START (Sr) condition and a STOP (P) condi-tion. Each word transmitted over the bus is 8 bits long and
is always followed by an acknowledge clock pulse.
The MAX9723 SDA line operates as both an input and an open-drain output. A pullup resistor, greater than 500Ω, is
required on the SDA bus. The MAX9723 SCL line oper-ates as an input only. A pullup resistor, greater than 500Ω,
is required on SCL if there are multiple masters on the bus,
or if the master in a single-master system has an open-
drain SCL output. Series resistors in line with SDA and
SCL are optional. Series resistors protect the digital inputs
of the MAX9723 from highvoltage spikes on the bus lines, and minimize crosstalk and undershoot of the bus signals.
Bit Transfer
One data bit is transferred during each SCL cycle. The
data on SDA must remain stable during the high period
of the SCL pulse. Changes in SDA while SCL is high are
control signals (see the START and STOP Conditions sec-
tion). SDA and SCL idle high when the I2C bus is not busy.
Start and Stop Conditions
SDA and SCL idle high when the bus is not in use. A mas-
ter device initiates communication by issuing a START
on SDA with SCL high. A STOP condition is a low-to-high transition on SDA while SCL is high (Figure 4). A START
condition from the master signals the beginning of trans-
mission to the MAX9723. The master terminates trans-
mission and frees the bus by issuing a STOP condition. The bus remains active if a REPEATED START condition
is generated instead of a STOP condition.
Early STOP Conditions
The MAX9723 recognizes a STOP condition at any point
during data transmission except if the STOP condition
occurs in the same high pulse as a START condition.
Slave Address
The MAX9723 is available with one of two preset slave addresses (see Table 1). The address is defined as the seven most significant bits (MSBs) followed by the Read/
Write (R/W) bit. The address is the first byte of informa-
tion sent to the MAX9723 after the START condition. The
MAX9723 is a slave device only capable of being written
to. The sent R/W bit must always be a zero when config-
uring the MAX9723.
The MAX9723 acknowledges the receipt of its address
even if R/W is set to 1. However, the MAX9723 will not
drive SDA. Addressing the MAX9723 with R/W set to 1
causes the master to receive all 1’s regardless of the
contents of the command register.
Acknowledge
The acknowledge bit (ACK) is a clocked 9th bit that the
Figure 3. 2-Wire Serial-Interface Timing Diagram
SCL
SDA
START
CONDITION
STOP
CONDITION
REPEATED
START
CONDITION
START
CONDITION
tHD, STA
tSU, STA
tHD, STAtSP
tBUF
tSU, STOtLOW
tSU, DAT
tHD, DAT
tHIGHtF
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C
data (see Figure 5). The MAX9723 pulls down SDA dur-
ing the master-generated 9th clock pulse. The SDA line
must remain stable and low during the high period of the
acknowledge clock pulse. Monitoring ACK allows for detec-
tion of unsuccessful data transfers. An unsuccessful data
transfer occurs if a receiving device is busy or if a system
fault has occurred. In the event of an unsuccessful data
transfer, the bus master may reattempt communication.
Write Data Format
A write to the MAX9723 includes transmission of a START
condition, the slave address with the R/W bit reset to 0 (see Table 1), one byte of data to configure the command
register, and a STOP condition. Figure 6 illustrates the
proper format for one frame.
The MAX9723 only accepts write data, but it acknowl-
edges the receipt of its address byte with the R/W bit set
high. The MAX9723 does not write to the SDA bus in the
event that the R/W bit is set high. Subsequently, the mas-
ter reads all 1’s from the MAX9723. Always reset the R/W bit to 0 to avoid this situation.
Command Register
The MAX9723 has one command register that is used to
enable/disable shutdown, enable/disable BassMax, and
set the maximum gain and volume. Table 2 describes the
function of the bits contained in the command register.
Reset B7 to 0 to shut down the MAX9723. The MAX9723
wakes up from shutdown when B7 is set to 1 provided
SHDN is high. SHDN must be high and B7 must be set to 1 for the MAX9723 to operate normally (see Table 3).
Set B6 to 1 to enable BassMax (see Table 4). The output
signal’s low-frequency response will be boosted accord-ing to the external components connected between OUT_
and BB_. See the BassMax Gain-Setting Components
section in the Applications Information section for details
on choosing the external components.
Figure 4. START, STOP, and REPEATED START ConditionsFigure 5. Acknowledge
Table 1. MAX9723 Address Map
Table 2. MAX9723 Command Register
Table 3. Shutdown Control, SHDN = 1
Table 4. BassMax Control
PARTMAX9723 SLAVE ADDRESSA5A4A3A2A1A0R/W
MAX9723A10011000
MAX9723B10011010
MAX9723C10011000
MAX9723D10011010B6B5B4B3B2B1B0
SHUTDOWNBassMax ENABLEMAXIMUM GAINVOLUME
MODEB7
MAX9723 Disabled0
MAX9723 Enabled1
MODEB6
BassMax Disabled0
BassMax Enabled1
SCL
SDASrPSCL
START
CONDITION
SDA89
CLOCK PULSE FOR
ACKNOWLEDGMENT
ACKNOWLEDGE
NOT ACKNOWLEDGE
MAX9723Stereo DirectDrive Headphone Ampliier
with BassMax, Volume Control, and I2C

Partno	Mfg	Dc	Qty	Available	Descript
MAX9723AETE+	MAIXM	N/a	2500	avai	Stereo DirectDrive® Headphone Amplifier with BassMax, Volume Control, and I²C
MAX9723DEBE+T	MAXIM Pb-free	N/a	20000	avai	Stereo DirectDrive® Headphone Amplifier with BassMax, Volume Control, and I²C
MAX9723DETE+ \|MAX9723DETE	MAXIM	N/a	1966	avai	Stereo DirectDrive® Headphone Amplifier with BassMax, Volume Control, and I²C
MAX9723DETE+T	MAXIM ?	N/a	45000	avai	Stereo DirectDrive® Headphone Amplifier with BassMax, Volume Control, and I²C
MAX9723DETE+TCJ6	MAXIM	N/a	2500	avai	Stereo DirectDrive® Headphone Amplifier with BassMax, Volume Control, and I²C