LM4891

1 Watt Audio Power Amplifier

General Description

The LM4891 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 watt of continuous average power to an 8

Ω BTL

load with less than 1% distortion (THD+N) from a 5V

DC

power supply.

Boomer audio power amplifiers were designed specifically to

provide high quality output power with a minimal amount of

external components. The LM4891 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 LM4891 features a low-power consumption shutdown

mode, which is achieved by driving the shutdown pin with

logic high. Additionally, the LM4891 features an internal ther-

mal shutdown protection mechanism.

The LM4891 contains advanced pop & click circuitry which

eliminates noises which would otherwise occur during

turn-on and turn-off transitions.

The LM4891 is unity-gain stable and can be configured by

external gain-setting resistors.

Key Specifications

Ω Load

62dB (typ)

1.0W (typ)

400mW (typ)

0.1µA (typ)

Features

n

Available in space-saving packages: micro SMD, MSOP,

SOIC, and LLP

n

Ultra low current shutdown mode

n

BTL output can drive capacitive loads

n

Improved pop & click circuitry eliminates noises during

turn-on and turn-off transitions

n

2.2 to 5.5V operation

n

No output coupling capacitors, snubber networks or

bootstrap capacitors required

n

Thermal shutdown protection

n

Unity-gain stable

n

External gain configuration capability

Applications

n

Mobile Phones

n

PDAs

n

Portable electronic devices

Typical Application

20007401

FIGURE 1. Typical Audio Amplifier Application Circuit

October 2002

© 2002 National Semiconductor Corporation

DS200074

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