MAX4410 Maxim, MAX4410 Datasheet - Page 12

• Manufacturer Part Number: MAX4410
• Description: 80mW / DirectDrive Stereo Headphone Driver with Shutdown
• Manufacturer: Maxim

80mW, DirectDrive Stereo Headphone Driver
with Shutdown
The MAX4410 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 (PV
(PV
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 V
unnecessary, improving frequency response while con-
serving board space and system cost.
Each channel has independent left/right, active-low
shutdown controls, making it possible to optimize
power savings in mixed-mode, mono/stereo operation.
The device features an undervoltage lockout that pre-
vents operation from an insufficient power supply and
click-and-pop suppression that eliminates audible tran-
sients on startup and shutdown. Additionally, the
MAX4410 features thermal overload and short-circuit
protection and can withstand ±8kV ESD strikes on the
output pins.
Traditional 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 MAX4410 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 MAX4410 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-Pump Capacitance and Load Resistance
graph in the Typical Operating Characteristics for
12
SS
______________________________________________________________________________________
). The headphone drivers operate from these bipo-
DD
/2. Thus, the large DC-blocking capacitors are
DD
Detailed Description
), creating a negative supply
DirectDrive
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 MAX4410 is typically 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:
1) When combining a microphone and headphone on
2) The sleeve is typically grounded to the chassis.
3) During an ESD strike, the driver’s ESD structures
Figure 1. Traditional Driver Output Waveform vs. MAX4410
Output Waveform
a single connector, the microphone bias scheme
typically requires a 0V reference.
Using this biasing approach, the sleeve must be
isolated from system ground, complicating product
design.
are the only path to system ground. Thus, the driver
must be able to withstand the full ESD strike.
V
V
OUT
OUT
CONVENTIONAL DRIVER-BIASING SCHEME
DirectDrive BIASING SCHEME
GND
V
V
GND
+V
-V
DD
DD
DD
DD
/2