MAX4409ETP ,1.8 to 3.6 V, 80 mW, directdrive, stereo headphone amplifier with common-mode senseFeaturesThe MAX4409 stereo headphone amplifier combines ♦ No Bulky DC-Blocking Capacitors RequiredM ..
MAX4409ETP+ ,80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode SenseELECTRICAL CHARACTERISTICS(V = V = 3V, V = V = 0, SHDN = SV , C1 = C2 = 2.2µF, R = R = R1 = R2 = 10 ..
MAX4409ETP+T ,80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode SenseApplications Functional DiagramNotebooksDirectDrive OUTPUTS Desktop PCs ELIMINATE DC-BLOCKING MAX44 ..
MAX4409EUD+ ,80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode SenseFeaturesThe MAX4409 stereo headphone amplifier combines♦ No Bulky DC-Blocking Capacitors Required®M ..
MAX440CPI ,High-Speed Video Multiplixer/AmplifierELECTRICAL CHARACTERISTICS
(V+ = 5V, V- = -5V, VNS = -5V, RL = 1500, TA = +25'C. unless otherwise ..
MAX440EPI ,High-Speed Video Multiplixer/AmplifierFeatures
. 160MHz Unity Galn Bandwidth
. 110MHz Bandwidth (Av = 6dB)
. 0.037004% Differential ..
MAX823REUK+T ,5-Pin Microprocessor Supervisory Circuits with Watchdog Timer and Manual ResetFeaturesThe MAX823/MAX824/MAX825* microprocessor (µP) ♦ Precision Monitoring of +2.5V, +3V, +3.3V, ..
MAX823REXK+T ,5-Pin Microprocessor Supervisory Circuits with Watchdog Timer and Manual ResetELECTRICAL CHARACTERISTICS(V = +4.75V to +5.5V for MAX82_L, V = +4.5V to +5.5V for MAX82_M, V = +3. ..
MAX823SEUK ,Microprocessor supervisory circuit. Reset threshold 2.93V. Active-low reset. Watchdog input. Manual reset input.FeaturesThe MAX823/MAX824/MAX825* microprocessor (µP) ' Precision Monitoring of +3V, +3.3V, and +5V ..
MAX823SEUK+T ,5-Pin Microprocessor Supervisory Circuits with Watchdog Timer and Manual ResetMAX823/MAX824/MAX82519-0487; Rev 5; 12/055-Pin Microprocessor Supervisory Circuits WithWatchdog Tim ..
MAX823SEUK-T ,5-Pin Microprocessor Supervisory Circuits with Watchdog Timer and Manual ResetMAX823/MAX824/MAX82519-0487; Rev 5; 12/055-Pin Microprocessor Supervisory Circuits WithWatchdog Tim ..
MAX823SEXK+ ,5-Pin Microprocessor Supervisory Circuits with Watchdog Timer and Manual ResetMAX823/MAX824/MAX82519-0487; Rev 5; 12/055-Pin Microprocessor Supervisory Circuits WithWatchdog Tim ..
MAX4409ETP
1.8 to 3.6 V, 80 mW, directdrive, stereo headphone amplifier with common-mode sense
General DescriptionThe MAX4409 stereo headphone amplifier combines
Maxim’s DirectDrive architecture and a common-mode
sense input, which allows the amplifier to reject com-
mon-mode noise. Conventional headphone amplifiers
require a bulky DC-blocking capacitor between the
headphone and the amplifier. DirectDrive produces a
ground-referenced output from a single supply, elimi-
nating the need for large DC-blocking capacitors,
which saves cost, board space, and component height.
The common-mode voltage sensing corrects for any
difference between SGND of the amplifier and the
headphone return. This feature minimizes ground-loop
noise when the HP socket is used as a line out connec-
tion to other grounded equipment, for example, a PC
connected to a home hi-fi system.
The MAX4409 draws only 5mA of supply current, deliv-
ers up to 80mW per channel into a 16Ωload, and has a
low 0.002% THD+N. A high 86dB power-supply rejec-
tion ratio allows this device to operate from noisy digital
supplies without additional power-supply conditioning.
The MAX4409 includes ±8kV ESD protection on the
headphone outputs. Comprehensive click-and-pop cir-
cuitry eliminates audible clicks and pops on startup
and shutdown. A low-power shutdown mode reduces
supply current draw to only 6µA.
The MAX4409 operates from a single 1.8V to 3.6V sup-
ply, has short-circuit and thermal overload protection,
and is specified over the extended -40°C to +85°C tem-
perature range. The MAX4409 is available in tiny 20-pin
thin QFN (4mm x 4mm x 0.8mm) and 14-pin TSSOP
packages.
Applications
FeaturesNo Bulky DC-Blocking Capacitors RequiredGround-Referenced Outputs Eliminate DC-Bias
Voltages on Headphone Ground PinCommon-Mode Voltage Sensing Eliminates
Ground-Loop Noise96dB CMRRNo Degradation of Low-Frequency Response Due
to Output Capacitors80mW per Channel into 16ΩLow 0.002% THD+NHigh 86dB PSRRIntegrated Click-and-Pop Suppression1.8V to 3.6V Single-Supply OperationLow Quiescent CurrentLow-Power Shutdown ModeShort-Circuit and Thermal-Overload Protection±8kV ESD-Protected Amplifier Outputs
Available in Space-Saving Packages
14-Pin TSSOP
20-Pin Thin QFN (4mm x 4mm x 0.8mm)
MAX4409
80mW, DirectDrive, Stereo Headphone
Amplifier with Common-Mode Sense
Functional Diagram
Ordering Information19-2842; Rev 1; 6/04
Notebooks
Desktop PCs
Cellular Phones
PDAs
MP3 Players
Tablet PCs
Portable Audio Equipment
Pin Configurations and Typical Application Circuit appear
at end of data sheet.*EP = Exposed paddle.
MAX4409
80mW, DirectDrive, Stereo Headphone
Amplifier with Common-Mode Sense
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(PVDD= SVDD= 3V, PGND = SGND = 0V, SHDN= SVDD, C1 = C2 = 2.2µF, RIN= RF= R1 = R2 = 10kΩ, RL= ∞, TA= TMINto TMAX,
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.
PGND to SGND.....................................................-0.3V to +0.3V
PVDDto SVDD.................................................................-0.3V to +0.3V
PVSSto SVSS.........................................................-0.3V to +0.3V
PVDDand SVDDto PGND or SGND.........................-0.3V to +4V
PVSSand SVSSto PGND or SGND..........................-4V to +0.3V
IN_ and COM to SGND.................................SVSSto (SVDD- 1V)
IN_ to COM.....................................(COM + 2V) to (COM - 0.3V)
SHDN_to SGND........................(SGND - 0.3V) to (SVDD+ 0.3V)
OUT_ to SGND............................(SVSS- 0.3V) to (SVDD+ 0.3V)
C1P to PGND.............................(PGND - 0.3V) to (PVDD+ 0.3V)
C1N to PGND.............................(PVSS- 0.3V) to (PGND + 0.3V)
Output Short Circuit to GND or VDD...........................Continuous
Continuous Power Dissipation (TA= +70°C)
14-Pin TSSOP (derate 9.1mW/°C above +70°C)..........727mW
20-Pin Thin QFN (derate 16.9mW/°C above +70°C)..1349mW
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
MAX4409
80mW, DirectDrive, Stereo Headphone
Amplifier with Common-Mode Sense
ELECTRICAL CHARACTERISTICS (continued)(PVDD= SVDD= 3V, PGND = SGND = 0V, SHDN= SVDD, C1 = C2 = 2.2µF, RIN= RF= R1 = R2 = 10kΩ, RL= ∞, TA= TMINto TMAX,
unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
Note 2:Inputs are connected to ground and COM.
Note 3:Inputs are AC-coupled to ground. COM is connected to ground.
ypical Operating Characteristics(C1 = C2 = 2.2µF, RIN= RF= R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
MAX4409
80mW, DirectDrive, Stereo Headphone
Amplifier with Common-Mode Sense
Typical Operating Characteristics (continued)(C1 = C2 = 2.2µF, RIN= RF= R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
MAX4409
80mW, DirectDrive, Stereo Headphone
Amplifier with Common-Mode Sense
Typical Operating Characteristics (continued)(C1 = C2 = 2.2µF, RIN= RF= R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
MAX4409
80mW, DirectDrive, Stereo Headphone
Amplifier with Common-Mode Sense
Typical Operating Characteristics (continued)(C1 = C2 = 2.2µF, RIN= RF= R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
MAX4409
80mW, DirectDrive, Stereo Headphone
Amplifier with Common-Mode Sense
Typical Operating Characteristics (continued)(C1 = C2 = 2.2µF, RIN= RF= R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
MAX4409
80mW, DirectDrive, Stereo Headphone
Amplifier with Common-Mode Sense
Typical Operating Characteristics (continued)(C1 = C2 = 2.2µF, RIN= RF= R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
MAX4409
80mW, DirectDrive, Stereo Headphone
Amplifier with Common-Mode Sense
Detailed DescriptionThe MAX4409 stereo headphone driver features Maxim’s
patented DirectDrive architecture, eliminating the large
output-coupling capacitors required by traditional single-
supply headphone drivers. The device consists of two
80mW Class AB headphone drivers, undervoltage lock-
out (UVLO)/shutdown control, charge-pump, and com-
prehensive click-and-pop suppression circuitry (see
Typical Application Circuit). The charge pump inverts the
positive supply (PVDD), creating a negative supply
(PVSS). The headphone drivers operate from these bipo-
lar supplies with their outputs biased about GND (Figure
1). The drivers have almost twice the supply range com-
pared to other 3V single-supply drivers, increasing the
available output power. The benefit of this GND bias is
that the driver outputs do not have a DC component typi-
cally VDD/2. Thus, the large DC-blocking capacitors are
unnecessary, improving frequency response while con-
serving board space and system cost.
The MAX4409 also features a common-mode voltage
sense input that corrects for mismatch between the
SGND of the device and the potential at the headphone
jack return. A low-power shutdown mode reduces sup-
ply current to 6µA. The device features an undervoltage
lockout that prevents operation from an insufficient
power supply and click-and-pop suppression that elim-
inates audible transients on startup and shutdown.
Additionally, the MAX4409 features thermal overload
and short-circuit protection and can withstand ±8kV
ESD strikes on the output pins.
Common-Mode SenseWhen the headphone jack is used as a line out to inter-
face between other equipment (notebooks, desktops,
and stereo receivers), potential differences between
the equipment grounds can create ground loops and
excessive ground current flow. The MAX4409 COM
input senses and corrects for the difference between
the headphone return and device ground. Connect
COM through a resistive voltage-divider between the
headphone jack return and SGND of the device (see
Typical Application Circuit). For optimum common-
mode rejection, use the same value resistors for R1 and
RIN, and R2 and RF. Improve DC CMRR by adding a
capacitor in between with SGND and R2 (see Typical
Application Circuit). If ground sensing is not required,
connect COM directly to SGND through a 5kΩresistor.
DirectDriveTraditional 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 this DC bias
from the headphone. Without these capacitors, a signif-
icant amount of DC current flows to the headphone,
resulting in unnecessary power dissipation and possi-
ble damage to both headphone and headphone driver.
Maxim’s patented DirectDrive architecture uses a
charge pump to create an internal negative supply volt-
age. This allows the outputs of the MAX4409 to be
biased about GND, almost doubling dynamic range
while operating from a single supply. With no DC com-
ponent, there is no need for the large DC-blocking
capacitors. Instead of two large (220µF, typ) tantalum
capacitors, the MAX4409 charge pump requires two
small ceramic capacitors, thereby conserving board
space, reducing cost, and improving the frequency
response of the headphone driver. See the Output
Power vs. Charge-Pump Capacitance and Load
Resistance graph in the Typical Operating Char-
acteristicsfor details of the possible capacitor sizes.
There is a low DC voltage on the driver outputs due to
amplifier offset. However, the offset of the MAX4409 is
MAX4409
80mW, DirectDrive, Stereo Headphone
Amplifier with Common-Mode Sensetypically 0.5mV, which, when combined with a 32Ω
load, results in less than 16µA of DC current flow to the
headphones.
Previous attempts to eliminate the output-coupling capac-
itors involved biasing the headphone return (sleeve) to
the DC-bias voltage of the headphone amplifiers. This
method raises some issues:When combining a microphone and headphone on
a single connector, the microphone bias scheme
typically requires a 0V reference.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. Thus, 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 con-
flict with the ground potential from other equipment,
resulting in possible damage to the drivers.
Low-Frequency ResponseIn addition to the cost and size disadvantages of the DC-
blocking capacitors required by conventional head-
phone amplifiers, these 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 form a highpass filter with the
-3dB point set by:
where RLis the headphone impedance and COUTis
the DC-blocking capacitor value. 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 larg-
er, more expensive capacitors. Figure 2 shows the
relationship between the size of COUTand the result-
ing 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 as a function of the
voltage change across the capacitor. At low fre-
quencies, the reactance of the capacitor dominates
at frequencies below the -3dB point and the voltage
coefficient appears as frequency-dependent distor-
tion. Figure 3 shows 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-
