October 2004
LM4879
1.1 Watt Audio Power Amplifier
General Description
Key Specifications
The LM4879 is an audio power amplifier primarily designed
for demanding applications in mobile phones and other por-
table communication device applications. It is capable of
delivering 1.1 watt of continuous average power to an 8Ω
BTL load with less than 1% distortion (THD+N) from a 5VDC
power supply.
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PSRR: 5V, 3V 217Hz
62dB (typ)
1.1W (typ)
Power Output at 5V & 1% THD+N
Power Output at 3V & 1% THD+N
Shutdown Current
350mW (typ)
0.1µA (typ)
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4879 does not require output
coupling capacitors or bootstrap capacitors, and therefore is
ideally suited for lower-power portable applications where
minimal space and power consumption are primary require-
ments.
Features
n No output coupling capacitors, snubber networks or
bootstrap capacitors required
n Unity gain stable
n Ultra low current shutdown mode
n Fast turn on: 80ms (typ), 110ms (max) with 1.0µF
capacitor
n BTL output can drive capacitive loads up to 100pF
n Advanced pop & click circuitry eliminates noises during
turn-on and turn-off transitions
n 2.2V - 5.0V operation
n Available in space-saving µSMD, LLP, and MSOP
packages
The LM4879 features a low-power consumption global shut-
down mode, which is achieved by driving the shutdown pin
with logic low. Additionally, the LM4879 features an internal
thermal shutdown protection mechanism.
The LM4879 contains advanced pop & click circuitry which
eliminates noises which would otherwise occur during
turn-on and turn-off transitions.
The LM4879 is unity-gain stable and can be configured by
external gain-setting resistors.
Applications
n Mobile Phones
n PDAs
n Portable electronic devices
Typical Application
20024301
FIGURE 1. Typical Audio Amplifier Application Circuit
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2004 National Semiconductor Corporation
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