LM4922 Datasheet, PDF (1/21 Pages) National Semiconductor (TI) – Ground-Referenced, Ultra Low Noise, Fixed Gain, 80mW Stereo Headphone Amplifier

December 2005
LM4922
Ground-Referenced, Ultra Low Noise, Fixed Gain, 80mW
Stereo Headphone Amplifier
General Description
The LM4922 is a ground referenced, fixed-gain audio power
amplifier capable of delivering 80mW of continuous average
power into a 16Ω single-ended load with less than 1%
THD+N from a 3V power supply.
The LM4922 features a new circuit technology that utilizes a
charge pump to generate a negative reference voltage. This
allows the outputs to be biased about ground, thereby elimi-
nating output-coupling capacitors typically used with normal
single-ended loads.
The LM4922 features an Automatic Standby Mode circuitry
(patent pending). In the absence of an input signal, after
approximately 12 seconds, the LM4922 goes into low cur-
rent standby mode. The LM4922 recovers into full power
operating mode immediately after a signal is applied to either
the left or right input pins. This feature saves power supply
current in battery operated applications.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4922 does not require output
coupling capacitors or bootstrap capacitors, and therefore is
ideally suited for mobile phone and other low voltage appli-
cations where minimal power consumption is a primary re-
quirement.
The LM4922 features a low-power consumption shutdown
mode selectable for either channel separately. This is ac-
complished by driving either the SD_RC (Shutdown Right
Channel) or SD_LC (Shutdown Left Channel) (or both) pins
with logic low, depending on which channel is desired shut-
down. Additionally, the LM4922 features an internal thermal
shutdown protection mechanism.
The LM4922 contains advanced pop & click circuitry that
eliminates noises which would otherwise occur during
turn-on and turn-off transitions.
The LM4922 has an internal fixed gain of 1.5V/V.
Key Specifications
j Improved PSRR at 217Hz
j Power Output at V_DD = 3V,
R_L = 16Ω, THD % 1%
j Shutdown Current
j Internal Fixed Gain
j Operating Voltage
70dB (typ)
80mW (typ)
0.01µA (typ)
1.5V/V (typ)
1.6V to 4.2V
Features
n Fixed Logic Levels
n Ground referenced outputs
n High PSRR
n Available in space-saving micro SMD package
n Ultra low current shutdown mode
n Improved pop & click circuitry eliminates noises during
turn-on and turn-off transitions
n No output coupling capacitors, snubber networks,
bootstrap capacitors, or gain-setting resistors required
n Shutdown either channel independently
Applications
n Notebook PCs
n Mobile Phone
n PDAs
n Portable electronic devices
n MP3 Players
Boomer^® is a registered trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation DS201582
www.national.com