max9721aetct Maxim Integrated Products, Inc., max9721aetct Datasheet - Page 6

• Manufacturer Part Number: max9721aetct
• Description: Max9721 1v, Fixed-gain, Directdrive, Stereo Headphone Amplifier With Shutdown
• Manufacturer: Maxim Integrated Products, Inc.

The MAX9721 stereo headphone driver features Maxim’s
patented DirectDrive architecture, eliminating the large
output-coupling capacitors required by conventional sin-
gle-supply headphone drivers. The MAX9721 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
(PV
Powering the drivers from V
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 MAX9721 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.
1V, Fixed-Gain, DirectDrive, Stereo Headphone
Amplifier with Shutdown
6
THIN
QFN
PIN
EP
10
11
12
SS
1
2
3
4
5
6
7
8
9
_______________________________________________________________________________________
) is created by inverting the positive supply (V
BUMP
UCSP
C4
C3
C2
C1
A1
A2
A3
A4
B4
B3
B1
B2
—
NAME
SGND
PGND
SHDN
OUTR
OUTL
PV
C1N
C1P
V
INR
V
INL
EP
DD
SS
SS
Detailed Description
Flying Capacitor Negative Terminal. Connect a 1µF capacitor from C1P to C1N.
Inverting Charge-Pump Output. Bypass with 1µF from PV
Left-Channel Audio Input
Right-Channel Audio Input
Amplifier Negative Power Supply. Must be connected to PV
Signal Ground. SGND must be connected to PGND. SGND is the ground reference for the input and
output signal.
Right-Channel Output
Left-Channel Output
Positive Power-Supply Input. Bypass with a 1µF capacitor to PGND.
Flying Capacitor Positive Terminal. Connect a 1µF capacitor from C1P to C1N.
Power Ground. Ground reference for the internal charge pump. PGND must be connected to SGND.
Active-Low Shutdown. Connect to V
charge pump.
Exposed Paddle. Internally connected to V
DD
and PV
SS
increases the
DD
).
DD
for normal operation. Pull low to disable the amplifier and
Conventional 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 MAX9721 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 16Ω load. The
MAX9721 provides 25mW to a 16Ω load. The
DirectDrive architecture eliminates the need for two
large (220µF, typ) DC-blocking capacitors on the out-
put. The MAX9721 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-
SS
. Leave paddle unconnected or solder to V
FUNCTION
SS
SS
to PGND. PV
.
SS
must be connected to V
Pin Description
SS
DirectDrive
.
SS
.