LM4920 Datasheet, PDF (1/17 Pages) National Semiconductor (TI) – Ground-Referenced, Ultra Low Noise, Fixed Gain, 80mW Stereo Headphone Amplifier

March 2006
LM4920
Ground-Referenced, Ultra Low Noise, Fixed Gain, 80mW
Stereo Headphone Amplifier
General Description
The LM4920 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 LM4920 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.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4920 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 LM4920 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 LM4920 features an internal thermal
shutdown protection mechanism.
The LM4920 contains advanced pop & click circuitry that
eliminates noises which would otherwise occur during
turn-on and turn-off transitions.
The LM4920 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 Mobile Phones
n MP3 Players
n PDAs
n Portable electronic devices
n Notebook PCs
Boomer^® is a registered trademark of National Semiconductor Corporation.
© 2006 National Semiconductor Corporation DS201793
www.national.com