LM4906

1W, Bypass-Capacitor-less Audio Amplifier with Internal

Selectable Gain

General Description

The LM4906 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 1W of continuous average power to an 8

Ω BTL

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

supply.

The LM4906 is the first National Semiconductor Boomer

Power Amplifier that does not require an external PSRR

bypass capacitor. The LM4906 also has an internal select-

able gain of either 6dB or 12dB. In addition, no output

coupling capacitors or bootstrap capacitors are required

which makes the LM4906 ideally suited for cell phone and

other low voltage portable applications.

The LM4906 contains advanced pop and click circuitry that

eliminates noise, which would otherwise occur during

turn-on and turn-off transitions.

Boomer audio power amplifiers were designed specifically to

provide high quality output power with a minimal amount of

external components. The LM4906 features a low -power

consumption shutdown mode (the part is enabled by pulling

the SD pin high). Additionally, the LM4906 features an inter-

nal thermal shutdown protection mechanism.

Key Specifications

71dB

Ω

1.0W (typ)

Ω 390mW (typ)

0.1µA (typ)

Features

n

Selectable gain of 6dB (2V/V) or 12dB (4V/V)

n

No output or PSRR bypass capacitors required

n

Improved “Click and Pop” suppression circuitry

n

Very fast turn on time: 5ms (typ)

n

Minimum external components

n

2.6 - 5.5V operation

n

BTL output can drive capacitive loads

n

Ultra low current shutdown mode (SD Low)

Applications

n

Portable computers

n

Desktop computers

n

Multimedia monitors

Typical Application

200571B9

FIGURE 1. Typical Audio Amplifier Application Circuit

May 2003

© 2003 National Semiconductor Corporation

DS200571

www.national.com