MAX9724BEBC+TG45 ,60mW, DirectDrive, Stereo Headphone Amplifier with Low RF Susceptibility and ShutdownELECTRICAL CHARACTERISTICS (continued)(V = 5V, PGND = SGND, SHDN = 5V, C1 = C2 = 1µF, R = ∞, resist ..
MAX9724BETC+ ,60mW, DirectDrive, Stereo Headphone Amplifier with Low RF Susceptibility and ShutdownMAX9724A/MAX9724B19-3597; Rev 6; 3/0960mW, DirectDrive, Stereo Headphone Amplifierwith Low RF Susce ..
MAX9724BETC+T ,60mW, DirectDrive, Stereo Headphone Amplifier with Low RF Susceptibility and ShutdownBlock DiagramsMAX9724BMAX9724ADirectDrive OUTPUTSDirectDrive OUTPUTSLEFTELIMINATE DC-BLOCKINGLEFTEL ..
MAX9724BETC+T ,60mW, DirectDrive, Stereo Headphone Amplifier with Low RF Susceptibility and ShutdownBlock DiagramsMAX9724BMAX9724ADirectDrive OUTPUTSDirectDrive OUTPUTSLEFTELIMINATE DC-BLOCKINGLEFTEL ..
MAX9725CETC ,1V, Low-Power, DirectDrive, Stereo Headphone Amplifier with ShutdownApplications VDDAA OR AAABATTERYMP3 Players Smart PhonesMAX9725Cellular Phones Portable Audio Equip ..
MAX9725CETC+T ,1V, Low-Power, DirectDrive, Stereo Headphone Amplifier with ShutdownBlock Diagrams continued at end of data sheet.UCSP is a trademark of Maxim Integrated Products, Inc ..
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
MAX9724AEBC+T-MAX9724AEBC+TG45-MAX9724AETC+-MAX9724AETC+T-MAX9724BEBC+TG45-MAX9724BETC+-MAX9724BETC+T
60mW, DirectDrive, Stereo Headphone Amplifier with Low RF Susceptibility and Shutdown
General DescriptionThe MAX9724A/MAX9724B stereo headphone ampli-
fiers are designed for portable equipment where board
space is at a premium. These devices use a unique
DirectDrive®architecture to produce a ground-refer-
enced output from a single supply, eliminating the need
for large DC-blocking capacitors, saving cost, board
space, and component height. The MAX9724 sup-
presses RF radiation received by input and supply
traces acting as antennas and prevents the amplifier
from demodulating the coupled noise. The MAX9724A
offers an externally adjustable gain while the
MAX9724B has an internally preset gain of -1.5V/V. The
MAX9724A/MAX9724B deliver up to 60mW per channel
into a 32Ωload and have low 0.02% THD+N. An 80dB
at 1kHz power-supply rejection ratio (PSRR) allows
these devices to operate from noisy digital supplies
without an additional linear regulator. Comprehensive
click-and-pop circuitry suppresses audible clicks and
pops on startup and shutdown.
The MAX9724A/MAX9724B operate from a single 2.7V
to 5.5V supply, consume only 3.5mA of supply current,
feature short-circuit and thermal-overload protection,
and are specified over the extended -40°C to +85°C
temperature range. The devices are available in tiny 12-
bump UCSP™ (1.5mm x 2mm) and 12-pin thin QFN
(3mm x 3mm x 0.8mm) packages.
Applications
FeaturesImproved RF Noise Rejection (Up to 67dB Over
Typical Amplifiers)No Bulky DC-Blocking Capacitors RequiredLow-Power Shutdown Mode, < 0.1µAAdjustable Gain (MAX9724A) or Fixed -1.5V/V
Gain (MAX9724B)Low 0.02% THD+NHigh PSRR (80dB at 1kHz) Eliminates LDOIntegrated Click-and-Pop Suppression2.7V to 5.5V Single-Supply OperationLow Quiescent Current (3.5mA)Available in Space-Saving Packages
12-Bump UCSP (1.5mm x 2mm)
12-Pin Thin QFN (3mm x 3mm x 0.8mm)
MAX9724A/MAX9724B
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and Shutdown
Ordering Information19-3597; Rev 6; 3/09
EVALUATION KIT
AVAILABLE
PARTGAIN
(V/V)
PIN-
PACKAGE
TOP
MARKMAX9724AEBC+TG45Adj.12 UCSP+ADH
MAX9724AETC+Adj.12 TQFN-EP*+AAT
MAX9724BEBC+TG45-1.512 UCSP+ADI
MAX9724BETC+-1.512 TQFN-EP*+AAU
Note:All devices specified over the -40°C to +85°C operating
range.
+Denoteslead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed paddle.Cellular Phones
MP3 Players
Notebook PCs
Handheld Gaming Consoles
LEFT
AUDIO
INPUT
RIGHT
AUDIO
INPUT
SHDN
MAX9724A
LEFT
AUDIO
INPUT
RIGHT
AUDIO
INPUT
MAX9724B
SHDN
DirectDrive OUTPUTS
ELIMINATE DC-BLOCKING
CAPACITORS
DirectDrive OUTPUTS
ELIMINATE DC-BLOCKING
CAPACITORS
FIXED GAIN ELIMINATES
EXTERNAL RESISTOR
NETWORK
Block Diagrams
Pin Configurations appear at end of data sheet.DVD Players
Smart Phones
PDAs
UCSP is a trademark of Maxim Integrated Products, Inc.DirectDrive is a registered trademark of Maxim Integrated
Products, Inc.
MAX9724A/MAX9724B
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and Shutdown
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.
VDDto GND..............................................................-0.3V to +6V
PVSSto SVSS.........................................................-0.3V to +0.3V
PGND to SGND.....................................................-0.3V to +0.3V
C1P to PGND..............................................-0.3V to (VDD+ 0.3V)
C1N to PGND............................................(PVSS- 0.3V) to +0.3V
PVSSand SVSSto PGND..........................................-6V to +0.3V
IN_ to SGND (MAX9724A)..........................-0.3V to (VDD+ 0.3V)
IN_ to SGND (MAX9724B).............(SVSS- 0.3V) to (VDD+ 0.3V)
OUT_ to SVSS(Note 1)....-0.3V to Min (VDD- SVSS+ 0.3V, +9V)
OUT_ to VDD(Note 2)......+0.3V to Max (SVSS- VDD- 0.3V, -9V)
SHDNto _GND.........................................................-0.3V to +6V
OUT_ Short Circuit to GND........................................Continuous
Short Circuit between OUTL and OUTR....................Continuous
Continuous Input Current into PVSS..................................260mA
Continuous Input Current (any other pin).........................±20mA
Continuous Power Dissipation (TA= +70°C, Multilayer board)
12-Bump UCSP (derate 6.5mW/°C above +70°C)........519mW
θJA................................................................................154 C/W
12-Pin TQFN (derate 16.7mW/°C above +70°C).........1333mW
θJA..................................................................................60°C/W
θJC..................................................................................11°C/W
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s).................................+300°C
Bump Temperature (soldering) Reflow............................+235°C
ELECTRICAL CHARACTERISTICS(VDD
= 5V, PGND = SGND, SHDN= 5V, C1 = C2 = 1µF, RL= ∞, resistive load reference to ground; for MAX9724A gain = -1.5V/V
(RIN= 20kΩ, RF= 30kΩ); for MAX9724B gain = -1.5V/V (internally set), TA= -40°C to +85°C, unless otherwise noted. Typical values
are at TA= +25°C, unless otherwise noted.) (Note 3)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
GENERALSupply Voltage RangeVDDGuaranteed by PSRR test2.75.5V
Quiescent CurrentICC3.55.5mA
Shutdown CurrentISHDNSHDN = SGND = PGND0.11µA
Shutdown to Full OperationtSON180µs
Input ImpedanceRINMAX9724B, measured at IN_121928kΩ
Output Offset VoltageVOS(Note 4)±1.5±10mV
VDD = 2.7V to 5.5V, TA = +25°C6986
f = 1kHz, 100mVP-P (Note 4)80Power-Supply Rejection RatioPSRR
f = 20kHz, 100mVP-P (Note 4)65
RL = 32Ω, THD+N = 1%3063Output Power (TQFN)POUTRL = 16Ω, THD+N = 1%42mW
RL = 32Ω, THD+N = 1%2545Output Power (UCSP)POUTRL = 16Ω, THD+N = 1%35mW
Voltage GainAVMAX9724B (Note 5)-1.52-1.5-1.48V/V
Channel-to-Channel Gain TrackingMAX9724B±0.15%
RL = 1kΩ, VOUT = 2VRMS, fIN = 1kHz0.003
RL = 32Ω, POUT = 50mW, fIN = 1kHz0.02Total Harmonic Distortion Plus
Noise (TQFN) (Note 6)THD+N
RL = 16Ω, POUT = 35mW, fIN = 1kHz0.04
RL = 1kΩ, VOUT = 2VRMS, fIN = 1kHz0.003
RL = 32Ω, POUT = 45mW, fIN = 1kHz0.03Total Harmonic Distortion Plus
Noise (UCSP) (Note 6)THD+N
RL = 16Ω, POUT = 32mW, fIN = 1kHz0.05
BW = 22Hz to 22kHz102RL = 1kΩ,
VOUT = 2VRMSA-weighted105
BW = 22Hz to 22kHz98Signal-to-Noise RatioSNRRL = 32Ω,
Note 1:OUTR and OUTL should be limited to no more than 9V above SVSS, or above VDD+ 0.3V, whichever limits first.
Note 2:OUTR and OUTL should be limited to no more than 9V below VDD, or below SVSS- 0.3V, whichever limits first.
MAX9724A/MAX9724B
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and Shutdown
ELECTRICAL CHARACTERISTICS (continued)(VDD
= 5V, PGND = SGND, SHDN= 5V, C1 = C2 = 1µF, RL= ∞, resistive load reference to ground; for MAX9724A gain = -1.5V/V
(RIN= 20kΩ, RF= 30kΩ); for MAX9724B gain = -1.5V/V (internally set), TA= -40°C to +85°C, unless otherwise noted. Typical values
are at TA= +25°C, unless otherwise noted.) (Note 3)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSSlew RateSR0.5V/µs
Capacitive DriveCLNo sustained oscillations100pF
CrosstalkL to R, R to L, f = 10kHz, RL = 16Ω,
POUT = 15mW-70dB
Charge-Pump Oscillator
FrequencyfOSC190270400kHz
Into shutdown-67
Click-and-Pop LevelKCP
RL = 32Ω, peak voltage,
A-weighted, 32 samples per
second (Notes 4, 7)
Out of
shutdown-64dB
DIGITAL INPUTS (SHDN)Input-Voltage HighVINH(TQFN only)2V
Input-Voltage LowVINL(TQFN only)0.8V
Input-Voltage HighVINH(UCSP only)1.4V
Input-Voltage LowVINL(UCSP only)0.9V
Input Leakage Current±1µA
ELECTRICAL CHARACTERISTICS(VDD
= 3V, PGND = SGND, SHDN= 3V, C1 = C2 = 1µF, RL= ∞, resistive load reference to ground; for MAX9724A gain = -1.5V/V
(RIN= 20kΩ, RF= 30kΩ); for MAX9724B gain = -1.5V/V (internally set), TA= -40°C to +85°C, unless otherwise noted. Typical values
are at TA= +25°C, unless otherwise noted.) (Note 3)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSQuiescent CurrentICC3.0mA
Shutdown CurrentISHDNSHDN = SGND = PGND0.1µA
f = 1kHz, 100mVP-P80Power-Supply Rejection Ratio
(Note 4)PSRRf = 20kHz, 100mVP-P65dB
RL = 32Ω, THD+N = 1%20Output Power (TQFN)POUTRL = 16Ω, THD+N = 1%14mW
RL = 32Ω, THD+N = 1%17Output Power (UCSP)POUTRL = 16Ω, THD+N = 1%12mW
RL = 1kΩ, VOUT = 2VRMS, fIN = 1kHz0.05
RL = 32Ω, POUT = 15mW, fIN = 1kHz0.03Total Harmonic Distortion Plus
Noise (TQFN) (Note 6)THD+N
RL = 16Ω, POUT = 10mW, fIN = 1kHz0.06
RL = 1kΩ, VOUT = 2VRMS, fIN = 1kHz0.003
RL = 32Ω, POUT = 15mW, fIN = 1kHz0.04Total Harmonic Distortion Plus
Noise (UCSP) (Note 6)THD+N
RL = 16Ω, POUT = 10mW, fIN = 1kHz0.06
Note 3:All specifications are 100% tested at TA= +25°C; temperature limits are guaranteed by design.
Note 4:The amplifier inputs are AC-coupled to GND.
Note 5:Gain for the MAX9724A is adjustable.
Note 6:Measurement bandwidth is 22Hz to 22kHz.
Note 7:Test performed with a 32Ωresistive load connected to GND. Mode transitions are controlled by SHDN. KCPlevel is calculated
as 20log[(peak voltage during mode transition, no input signal)/(peak voltage under normal operation at rated power level)].
MAX9724A/MAX9724B
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and Shutdown
Typical Operating Characteristics(VDD= 5V, PGND = SGND = 0V, SHDN= VDD, C1 = C2 = 1µF, RL= ∞, gain = -1.5V/V (RIN= 20kΩ, RF= 30kΩfor the MAX9724A),
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA= +25°C, unless otherwise noted.)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (TQFN)
MAX9724 toc01
OUTPUT POWER (mW)
THD+N (%)
VDD = 3V
RL = 16Ω
fIN = 1kHz
fIN = 20Hz
fIN = 10kHz51525102030
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (UCSP)
MAX9724 toc02
OUTPUT POWER (mW)
THD+N (%)
VDD = 3V
RL = 16Ω
fIN = 1kHz
fIN = 20Hz
fIN = 10kHz
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (TQFN)
MAX9724toc03
OUTPUT POWER (mW)
THD+N (%)
VDD = 3V
RL = 32Ω
fIN = 1kHz
fIN = 20Hz
fIN = 10kHz15102025303540
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (USCP)
MAX9724toc04
OUTPUT POWER (mW)
THD+N (%)
VDD = 3V
RL = 32Ω
fIN = 1kHzfIN = 10kHz
fIN = 20Hz
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (TQFN)
MAX9724 toc05
OUTPUT POWER (mW)
THD+N (%)
VDD = 5V
RL = 16Ω
fIN = 1kHz
fIN = 20Hz
fIN = 10kHz
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (UCSP)
MAX9724 toc06
OUTPUT POWER (mW)
THD+N (%)
VDD = 5V
RL = 16Ω
fIN = 1kHz
fIN = 20Hz
fIN = 10kHz
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (TQFN)
MAX9724 toc07
THD+N (%)
VDD = 5V
RL = 32Ω
fIN = 1kHz
fIN = 20Hz
fIN = 10kHz
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (UCSP)
MAX9724 toc08
THD+N (%)
VDD = 5V
RL = 32Ω
fIN = 1kHz
fIN = 20Hz
fIN = 10kHz1k10010k100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (TQFN) MAX9724 toc09
THD+N (%)
VDD = 3V
RL = 16Ω
POUT = 5mW
POUT = 10mW
MAX9724A/MAX9724B
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and Shutdown
Typical Operating Characteristics (continued)(VDD= 5V, PGND = SGND = 0V, SHDN= VDD, C1 = C2 = 1µF, RL= ∞, gain = -1.5V/V (RIN= 20kΩ, RF= 30kΩfor the MAX9724A),
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA= +25°C, unless otherwise noted.)1k10010k100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (UCSP) MAX9724 toc10
FREQUENCY (Hz)
THD+N (%)
VDD = 3V
RL = 16ΩPOUT = 5mW
POUT = 10mW1k10010k100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (TQFN)MAX9724 toc11
FREQUENCY (Hz)
THD+N (%)
VDD = 3V
RL = 32Ω
POUT = 8mW
POUT = 15mW1k10010k100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (UCSP)MAX9724 toc12
FREQUENCY (Hz)
THD+N (%)
VDD = 3V
RL = 32Ω
POUT = 8mW
POUT = 13mW1k10010k100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (TQFN) MAX9724 toc13
FREQUENCY (Hz)
THD+N (%)
VDD = 5V
RL = 16Ω
POUT = 20mW
POUT = 37mW1k10010k100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (UCSP) MAX9724 toc14
FREQUENCY (Hz)
THD+N (%)
VDD = 5V
RL = 16Ω
POUT = 20mW
POUT = 32mW1k10010k100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (TQFN) MAX9724 toc15
FREQUENCY (Hz)
THD+N (%)
VDD = 5V
RL = 32Ω
POUT = 50mW
POUT = 30mW1k10010k100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (UCSP) MAX9724 toc16
THD+N (%)
VDD = 5V
RL = 32Ω
POUT = 45mW
POUT = 20mW
OUTPUT POWER
vs. SUPPLY VOLTAGE (TQFN)
MAX9724 toc17
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
fIN = 1kHz
RL = 16Ω
1% THD+N
10% THD+N
OUTPUT POWER
vs. SUPPLY VOLTAGE (UCSP)
MAX9724 toc18
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
fIN = 1kHz
RL = 16Ω
1% THD+N
10% THD+N
MAX9724A/MAX9724B
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and Shutdown
Typical Operating Characteristics (continued)(VDD= 5V, PGND = SGND = 0V, SHDN= VDD, C1 = C2 = 1µF, RL= ∞, gain = -1.5V/V (RIN= 20kΩ, RF= 30kΩfor the MAX9724A),
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA= +25°C, unless otherwise noted.)
OUTPUT POWER
vs. SUPPLY VOLTAGE (TQFN)
MAX9724 toc19
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
fIN = 1kHz
RL = 32Ω
1% THD+N
10% THD+N
OUTPUT POWER
vs. SUPPLY VOLTAGE (UCSP)
MAX9724 toc20
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
fIN = 1kHz
RL = 32Ω
1% THD+N
10% THD+N1001000
OUTPUT POWER
vs. LOAD RESISTANCE (TQFN)MAX9724 toc21
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
VDD = 3V
fIN = 1kHz
1% THD+N
10% THD+N1001000
OUTPUT POWER
vs. LOAD RESISTANCE (UCSP)MAX9724 toc22
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
VDD = 3V
fIN = 1kHz
THD+N = 1%
THD+N = 10%
OUTPUT POWER
vs. LOAD RESISTANCE (TQFN)
MAX9724 toc23
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)30
THD+N = 1%
VDD = 5V
fIN = 1kHz
THD+N = 10%
OUTPUT POWER
vs. LOAD RESISTANCE (UCSP)
MAX9724 toc24
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)30
THD+N = 1%
VDD = 5V
fIN = 1kHz
THD+N = 10%
POWER DISSIPATION
vs. OUTPUT POWER (TQFN)
MAX9724t oc25
POWER DISSIPATION (mW)
VDD = 3V
fIN = 1kHz
POUT = POUTL + POUTR
OUTPUTS IN PHASE
RL = 16Ω
RL = 32Ω
POWER DISSIPATION
vs. OUTPUT POWER (UCSP)
MAX9724t oc26
POWER DISSIPATION (mW)
VDD = 3V
fIN = 1kHz
POUT = POUTL + POUTR
OUTPUTS IN PHASE
RL = 16Ω
RL = 32Ω
-12010010k100k
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCYMAX9724 toc27
PSRR (dB)
VDD = 5V
VDD = 3V
RL = 32Ω
MAX9724A/MAX9724B
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and Shutdown-12010010k100k
CROSSTALK vs. FREQUENCYMAX9724 toc28
FREQUENCY (Hz)
CROSSTALK (dB)
RIGHT TO LEFT
LEFT TO RIGHT
POUT = 15mW
RL = 16Ω10015050
OUTPUT POWER vs. LOAD RESISTANCE AND
CHARGE-PUMP CAPACITOR SIZE (TQFN)MAX9724 toc29
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
VDD = 5V
fIN = 1kHz
THD+N = 1%
C1 = C2 = 2.2μFC1 = C2 = 1μF
C1 = C2 = 0.47μF10015050
OUTPUT POWER vs. LOAD RESISTANCE AND
CHARGE-PUMP CAPACITOR SIZE (UCSP)MAX9724 toc30
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
VDD = 5V
fIN = 1kHz
THD+N = 1%
C1 = C2 = 2.2μF
C1 = C2 = 1μF
C1 = C2 = 0.47μF
OUTPUT SPECTRUM vs. FREQUENCY
MAX9724 toc31
FREQUENCY (kHz)
AMPLITUDE (dBV)
RL = 32Ω
VDD = 3V
fIN = 1kHz
VOUT = -60dBV
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9724 toc32
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
NO LOAD
INPUTS
GROUND
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE (TQFN)MAX9724 toc33
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT (nA)
NO LOAD INPUTS GND
Typical Operating Characteristics (continued)(VDD= 5V, PGND = SGND = 0V, SHDN= VDD, C1 = C2 = 1µF, RL= ∞, gain = -1.5V/V (RIN= 20kΩ, RF= 30kΩfor the MAX9724A),
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA= +25°C, unless otherwise noted.)
MAX9724A/MAX9724B
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and Shutdown
Pin Description
PIN
TQFNUCSP
NAMEFUNCTIONC1C1PFlying Capacitor Positive Terminal. Connect a 1µF ceramic capacitor from C1P to C1N.C2PGNDPower Ground. Connect to SGND.C3C1NFlying Capacitor Negative Terminal. Connect a 1µF ceramic capacitor from C1P to C1N.
4C4PVSSCharge-Pump Output. Connect to SVSS and bypass with a 1µF ceramic capacitor to PGND.
5A2SHDNActive-Low Shutdown InputB3INLLeft-Channel InputA1SGNDSignal Ground. Connect to PGND.B2INRRight-Channel Input
9B4SVSSAmplifier Negative Supply. Connect to PVSS.A3OUTRRight-Channel OutputA4OUTLLeft-Channel OutputB1VDDPositive Power-Supply Input. Bypass with a 1µF capacitor to PGND.—EPExposed Paddle. Internally connected to SVSS. Connect to SVSS or leave unconnected.
EXITING SHUTDOWNMAX9724 toc34VSHDN
5V/div
VOUT_
500mV/div
VIN_
1V/div
40μs/div
ENTERING SHUTDOWNMAX9724 toc35VSHDN
5V/div
VOUT_
500mV/div
VIN_
1V/div
20μs/div
Typical Operating Characteristics (continued)(VDD= 5V, PGND = SGND = 0V, SHDN= VDD, C1 = C2 = 1µF, RL= ∞, gain = -1.5V/V (RIN= 20kΩ, RF= 30kΩfor the MAX9724A),
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA= +25°C, unless otherwise noted.)
MAX9724A/MAX9724B
Detailed DescriptionThe MAX9724A/MAX9724B stereo headphone ampli-
fiers feature Maxim’s DirectDrive architecture, eliminat-
ing the large output-coupling capacitors required by
conventional single-supply headphone amplifiers. The
device consists of two 60mW Class AB headphone
amplifiers, undervoltage lockout (UVLO)/shutdown con-
trol, charge pump, and comprehensive click-and-pop
suppression circuitry (see the Functional
Diagram/Typical Operating Circuits). The charge pump
inverts the positive supply (VDD), creating a negative
supply (PVSS). The headphone amplifiers operate from
these bipolar supplies with their outputs biased about
PGND (Figure 1). The benefit of this PGND bias is that
the amplifier outputs do not have a DC component. The
large DC-blocking capacitors required with convention-
al headphone amplifiers are unnecessary, conserving
board space, reducing system cost, and improving fre-
quency response. The MAX9724A/MAX9724B feature
an undervoltage lockout that prevents operation from
an insufficient power supply and click-and-pop sup-
pression that eliminates audible transients on startup
and shutdown. The MAX9724A/MAX9724B also feature
thermal-overload and short-circuit protection.
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 headphone. Without these capacitors, a
significant amount of DC current flows to the head-
phone, 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, allowing
the MAX9724A/MAX9724B outputs to be biased about
GND. With no DC component, there is no need for the
large DC-blocking capacitors. The MAX9724A/
MAX9724B charge pumps require two small ceramic
capacitors, conserving board space, reducing cost,
and improving the frequency response of the head-
phone amplifier. See the Output Power vs. Load
Resistance and Charge-Pump Capacitor Size graph in
the Typical Operating Characteristicsfor details of the
possible capacitor sizes. There is a low DC voltage on
the amplifier outputs due to amplifier offset. However,
the offsets of the MAX9724A/MAX9724B are typically
1.5mV, which, when combined with a 32Ωload, results
in less than 47µA of DC current flow to the head-
phones.
Charge PumpThe MAX9724A/MAX9724B feature a low-noise charge
pump. The 270kHz switching frequency is well beyond
the audio range and does not interfere with audio sig-
nals. The switch drivers feature a controlled switching
speed that minimizes noise generated by turn-on and
turn-off transients. The di/dt noise caused by the para-
sitic bond wire and trace inductance is minimized by
limiting the switching speed of the charge pump.
Although not typically required, additional high-fre-
quency noise attenuation can be achieved by increas-
ing the value of C2 (see the Functional Diagram/Typical
Operating Circuits).
RF SusceptibilityModern audio systems are often subject to RF radiation
from sources like wireless networks and cellular phone
networks. Although the RF radiation is out of the audio
band, many signals, in particular GSM signals, contain
bursts or modulation at audible frequencies. Most ana-
log amplifiers demodulate the low-frequency envelope,
adding noise to the audio signal. The architecture of
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and ShutdownVDD
-VDD
GND
VOUT
CONVENTIONAL DRIVER-BIASING SCHEME
DirectDrive BIASING SCHEME
VDD/2
VDD
VDD
GND
VOUT
2VDD
Figure1. Conventional Driver Output Waveform vs.
MAX9724A/MAX9724B Output Waveform
MAX9724A/MAX9724Bthe MAX9724 addresses the problem of the RF suscep-
tibility by rejecting RF noise and preventing it from cou-
pling into the audio band.
The RF susceptibility of an amplifier can be measured
by placing the amplifier in an isolated chamber and sub-
jecting it to an electric field of known strength. If the
electric field is modulated with an audio band signal, a
percentage of the modulated signal will be demodulat-
ed and amplified by the device in the chamber. Figure 2
shows the signal level at the outputs of an unoptimized
amplifier and the MAX9724. The test conditions are
shown in Table 1.
Click-and-Pop SuppressionIn conventional single-supply audio amplifiers, the out-
put-coupling capacitor contributes significantly to audi-
ble clicks and pops. Upon startup, the amplifier charges
the coupling capacitor to its bias voltage, typically half
the supply. Likewise, on shutdown, the capacitor is dis-
charged. This results in a DC shift across the capacitor,
which appears as an audible transient at the speaker.
Since the MAX9724A/ MAX9724B do not require output-
coupling capacitors, this problem does not arise.
Additionally, the MAX9724A/MAX9724B feature exten-
sive click-and-pop suppression that eliminates any audi-
ble transient sources internal to the device.
Typically, the output of the device driving the
MAX9724A/MAX9724B has a DC bias of half the supply
voltage. At startup, the input-coupling capacitor, CIN, is
charged to the preamplifier’s DC bias voltage through
the MAX9724A/MAX9724B input resistor, RIN, and a
series 15kΩresistor. This DC shift across the capacitor
results in an audible click-and-pop. Delay the rise of
SHDN4 to 5 time constants based on RINx 15kΩx CIN
to eliminate clicks-and-pops caused by the input filter.
ShutdownThe MAX9724A/MAX9724B feature a < 0.1µA, low-
power shutdown mode that reduces quiescent current
consumption and extends battery life for portable appli-
cations. Drive SHDNlow to disable the amplifiers and
the charge pump. In shutdown mode, the amplifier out-
put impedance is set to 14kΩ||RF(RFis 30kΩfor the
MAX9724B). The amplifiers and charge pump are
enabled once SHDNis driven high.
Applications Information
Power DissipationUnder normal operating conditions, linear power ampli-
fiers can dissipate a significant amount of power. The
maximum power dissipation for each package is given
in the Absolute Maximum Ratingssection under
Continuous Power Dissipation or can be calculated by
the following equation:
where TJ(MAX) is +150°C, TAis the ambient tempera-
ture, and θJAis the reciprocal of the derating factor inTT
DISSPKGMAXMAXA()=−
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and Shutdown
TEST PARAMETERSETTINGRF Field Strength50V/m
RF Modulation TypeSine wave
RF Modulation Index100%
RF Modulation Frequency1kHz
Table 1. RF Susceptibility Test ConditionsMAX9724 fig02
RF CARRIER FREQUENCY (MHz)
AMPLIFIER OUTPUT AMPLITUDE (dBV)
RF SUSCEPTIBLE
AMPLIFIER
MAX9724
62dB IMPROVEMENT
AT 850MHz
39dB IMPROVEMENT
AT 900MHz
67dB IMPROVEMENT
AT 1800MHz
49dB IMPROVEMENT
AT 1900MHz
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