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 ..
MAX9725EEBC+TG45 ,1V, Low-Power, DirectDrive, Stereo Headphone Amplifier with ShutdownFeatures♦ Low Quiescent CurrentThe MAX9725A–MAX9725D fixed-gain, stereo head-2.1mA (MAX9725A–MAX972 ..
MAX9726AETP+ ,DirectDrive, Headphone Amplifier with BassMax, I²C, Volume and Gain ControlELECTRICAL CHARACTERISTICS (5V Supply)(V = SHDN = 5V, PGND = SGND = 0V, C1 = C2 = 1µF, C = C = 1µF, ..
MAX9726AETP+T ,DirectDrive, Headphone Amplifier with BassMax, I²C, Volume and Gain ControlApplicationsBassMaxBMLSCL2I C SDAINTERFACEFBLINLOUTLΣVOLUMECONTROLOUTRΣINRFBRMAX9726BMRBassMaxSMBus ..
MAX9726BETP+T ,DirectDrive, Headphone Amplifier with BassMax, I²C, Volume and Gain Controlfeatures Maxim’s♦ Short-Circuit and Thermal-Overload Protectionindustry-leading click-and-pop suppr ..
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
MAX9725CETC
1V, Low-Power, DirectDrive, Stereo Headphone Amplifier with Shutdown
General DescriptionThe MAX9725 fixed-gain, stereo headphone amplifier
is ideal for portable equipment where board space is at a
premium. The MAX9725 uses a unique, patented
DirectDriveTMarchitecture to produce a ground-referenced
output from a single supply, eliminating the need for large
DC-blocking capacitors, saving cost, board space, and
component height. Fixed gains of -2V/V (MAX9725A),
1.5V/V (MAX9725B), -1V/V (MAX9725C), and -4V/V
(MAX9725D) further reduce external component count.
The MAX9725 delivers up to 20mW per channel into a
32Ωload and achieves 0.006% THD+N. An 80dB at 1kHz
power-supply rejection ratio (PSRR) allows the MAX9725
to operate from noisy digital supplies without an additional
linear regulator. The MAX9725 includes ±8kV ESD protec-
tion on the headphone output. Comprehensive click-and-
pop circuitry suppresses audible clicks and pops at
startup and shutdown. A low-power shutdown mode
reduces supply current to 0.6µA (typ).
The MAX9725 operates from a single 0.9V to 1.8V supply,
allowing the device to be powered directly from a single
AA or AAA battery. The MAX9725 consumes only
2.1mA of supply current, provides short-circuit protection,
and is specified over the extended -40°C to +85°C tem-
perature range. The MAX9725 is available in a tiny
(1.54mm x 2.02mm x 0.6mm) 12-bump chip-scale
package (UCSP™) and a 12-pin thin QFN package
(4mm x 4mm x 0.8mm).
Applications
FeaturesLow Quiescent Current (2.1mA)Single-Cell, 0.9V to 1.8V Single-Supply OperationFixed Gain Eliminates External Feedback Network
MAX9725A: -2V/V
MAX9725B: -1.5V/V
MAX9725C: -1V/V
MAX9725D: -4V/VGround-Referenced Outputs Eliminate DC BiasNo Degradation of Low-Frequency Response Due
to Output Capacitors20mW per Channel into 32ΩLow 0.006% THD+NHigh PSRR (80dB at 1kHz)Integrated Click-and-Pop SuppressionLow-Power Shutdown ControlShort-Circuit Protection±8kV ESD-Protected Amplifier Outputs
Available in Space-Saving Packages
12-Bump UCSP (1.54mm x 2.02mm x 0.6mm)
12-Pin Thin QFN (4mm x 4mm x 0.8mm)
MAX9725, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown19-3465; Rev 0; 11/04
Ordering InformationUCSP is a trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.*Future product—contact factory for availability.
**EP = Exposed paddle.
MP3 Players
Cellular Phones
PDAs
Smart Phones
Portable Audio Equipment
Block Diagram
MAX9725, Low-Power, DirectDrive, Stereo Headphone
Amplifier with 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.
SGND to PGND.....................................................-0.3V to +0.3V
VDDto SGND or PGND............................................-0.3V to +2V
VSSto PVSS...........................................................-0.3V to +0.3V
C1P to PGND..............................................-0.3V to (VDD+ 0.3V)
C1N to PGND............................................(PVSS- 0.3V) to +0.3V
VSS, PVSSto GND....................................................+0.3V to -2V
OUTR, OUTL, INR, INL to SGND.....(VSS- 0.3V) to (VDD+ 0.3V)
SHDNto SGND or PGND.........................................-0.3V to +4V
Output Short-Circuit Current......................................Continuous
Continuous Power Dissipation (TA= +70°C)
12-Bump UCSP (derate 6.5mW/°C above +70°C)....518.8mW
12-Pin Thin QFN (derate 16.9mW/°C above +70°C)..1349.1mW
Junction Temperature......................................................+150°C
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Bump Temperature (soldering) Reflow............................+230°C
Lead Temperature (soldering, 10s).................................+300°C
ELECTRICAL CHARACTERISTICS(VDD= 1.5V, PGND = SGND = 0V, VSHDN= 1.5V, VSS= PVSS, C1 = C2 = 1µF, CIN= 1µF, RL= ∞, TA= TMINto TMAX, unless otherwise
noted. Typical values are at TA= +25°C.) (See the Functional Diagram.)
MAX9725, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
Note 2:fIN= 1kHz, TA= +25°C, THD+N < 1%, both channels driven in-phase.
Note 3:Testing performed with 32Ωresistive load connected to outputs. Mode transitions controlled by SHDN. KCPlevel calculated
as 20 log [peak voltage under normal operation at rated power level / peak voltage during mode transition]. Inputs are AC-
grounded.
Typical Operating Characteristics(VDD= 1.5V, PGND = SGND = 0V, VSHDN= 1.5V, VSS= PVSS, C1 = C2 = 1µF, CIN= 1µF, THD+N measurement bandwidth = 22Hz
ELECTRICAL CHARACTERISTICS (continued)(VDD= 1.5V, PGND = SGND = 0V, VSHDN= 1.5V, VSS= PVSS, C1 = C2 = 1µF, CIN= 1µF, RL= ∞, TA= TMINto TMAX, unless otherwise
noted. Typical values are at TA= +25°C.) (See the Functional Diagram.)
MAX9725, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
Typical Operating Characteristics (continued)(VDD= 1.5V, PGND = SGND = 0V, VSHDN= 1.5V, VSS= PVSS, C1 = C2 = 1µF, CIN= 1µF, THD+N measurement bandwidth = 22Hz
to 22kHz, TA= +25°C, unless otherwise noted.) (See the Functional Diagram.)
MAX9725, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown1020304050
POWER DISSIPATION
vs. OUTPUT POWERMAX9725 toc16
OUTPUT POWER (mW)
POWER DISSIPATION (mW)5101520
POWER DISSIPATION
vs. OUTPUT POWERMAX9725 toc17
OUTPUT POWER (mW)
POWER DISSIPATION (mW)10010k1k100k
GAIN FLATNESS
vs. FREQUENCYFREQUENCY (Hz)
AMPLITUDE (dB)
MAX9725 toc1820304050
OUTPUT POWER vs. CHARGE-PUMP
CAPACITANCE AND LOAD RESISTANCEMAX9725 toc19
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
OUTPUT SPECTRUM
vs. FREQUENCY
MAX9725 toc20
FREQUENCY (kHz)
AMPLITUDE (dB)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX9725 toc21
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGEMAX9725 toc22
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT (
EXITING SHUTDOWN
MAX9725 toc23
200µs/div
OUT_
1V/div
SHDN
500mV/div
POWER-UP/-DOWN WAVEFORMMAX9725toc24
200ms/div
OUT_
10mV/div
VDD
1V/div
Typical Operating Characteristics (continued)(VDD= 1.5V, PGND = SGND = 0V, VSHDN= 1.5V, VSS= PVSS, C1 = C2 = 1µF, CIN= 1µF, THD+N measurement bandwidth = 22Hz
to 22kHz, TA= +25°C, unless otherwise noted.) (See the Functional Diagram.)
MAX9725
Detailed DescriptionThe MAX9725 stereo headphone driver features Maxim’s
patented DirectDrive architecture, eliminating the large
output-coupling capacitors required by conventional sin-
gle-supply headphone drivers. The MAX9725 consists of
two 20mW class AB headphone drivers, shutdown con-
trol, inverting charge pump, internal gain-setting resistors,
and comprehensive click-and-pop suppression circuitry
(see the Functional Diagram). A negative power supply
(PVSS) is created by inverting the positive supply (VDD).
Powering the drivers from VDDand PVSSincreases the
dynamic range of the drivers to almost twice that of other
1V single-supply drivers. This increase in dynamic range
allows for higher output power.
The outputs of the MAX9725 are biased about GND
(Figure 1). The benefit of this GND bias is that the driver
outputs do not have a DC component, thus large DC-
blocking capacitors are unnecessary. Eliminating the
DC-blocking capacitors on the output saves board
space, system cost, and improves frequency response.
DirectDriveConventional single-supply headphone drivers have their
outputs biased about a nominal DC voltage (typically half
the supply) for maximum dynamic range. Large coupling
capacitors are needed to block the DC bias from the
headphones. 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 driver.
Maxim’s DirectDrive architecture uses a charge pump
to create an internal negative supply voltage. This
allows the MAX9725 outputs to be biased about GND,
increasing the dynamic range while operating from a
single supply. A conventional amplifier powered from
1.5V ideally provides 18mW to a 16Ωload. The
MAX9725 provides 25mW to a 16Ωload. The
DirectDrive architecture eliminates the need for two
large (220µF, typ) DC-blocking capacitors on the out-
put. The MAX9725 charge pump requires two small
ceramic capacitors, conserving board space, reducing
cost, and improving the frequency response of the
headphone driver. See the Output Power vs. Charge-
, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
Pump Capacitance and Load Resistance graph in the
Typical Operating Characteristics for details of the possi-
ble capacitor sizes.
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 raises 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 driver’s ESD structures
are the only path to system ground. The driver must
be able to withstand the full ESD strike.When using the headphone jack as a line out to
other equipment, the bias voltage on the sleeve may
conflict with the ground potential from other equip-
ment, resulting in possible damage to the drivers.
Low-Frequency ResponseLarge DC-blocking capacitors limit the amplifier’s low-
frequency response and can distort the audio signal:The impedance of the headphone load and the DC-
blocking capacitor forms a highpass filter with the
-3dB point set by:
where RLis the impedance of the headphone and
COUTis the value of the DC-blocking capacitor. The
highpass filter is required by conventional single-
ended, single power-supply headphone drivers to
block the midrail DC-bias component of the audio
signal from the headphones. The drawback to the
filter is that it can attenuate low-frequency signals.
Larger values of COUTreduce this effect but result
in physically larger, more expensive capacitors.
Figure 2 shows the relationship between the size of
COUTand the resulting low-frequency attenuation.
Note that the -3dB point for a 16Ωheadphone with
a 100µF blocking capacitor is 100Hz, well within the
normal audio band, resulting in low-frequency
attenuation of the reproduced signal.The voltage coefficient of the DC-blocking capacitor
contributes distortion to the reproduced audio signal
as the capacitance value varies when the function of
the voltage across the capacitor changes. At low
frequencies, the reactance of the capacitor domi-
nates at frequencies below the -3dB point and the
voltage coefficient appears as frequency-dependent
distortion. Figure 3shows the THD+N introduced by
two different capacitor dielectric types. Note that
below 100Hz, THD+N increases rapidly.
The combination of low-frequency attenuation and fre-
quency-dependent distortion compromises audio
reproduction in portable audio equipment that empha-
sizes low-frequency effects such as multimedia lap-
tops, as well as MP3, CD, and DVD players. These
low-frequency, capacitor-related deficiencies are elimi-
nated by using DirectDrive technology.
Charge PumpThe MAX9725 features a low-noise charge pump. The
580kHz 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. The di/dt noise caused by the parasitic bond
wire and trace inductance is minimized by limiting the
turn-on/off speed of the charge pump. Additional high-
MAX9725, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
