LM4912

Stereo 40mW Low Noise Headphone Amplifier

General Description

The LM4912 is an stereo audio power amplifier capable of

delivering 40mW per channel of continuous average power

into a 16

Ω load or 25mW per channel into a 32Ω load at 1%

THD form a 3V power supply.

Boomer audio power amplifiers were designed specifically to

provide high quality output power with a minimal amount of

external components. Since the LM4912 does not require

bootstrap capacitors or snubber networks, it is optimally

suited for low-power portable systems.

The LM4912 features a low-power consumption shutdown

mode and a power mute mode that allows for faster turn on

time with less than 1mV voltage change at outputs on re-

lease. Additionally, the LM4912 features an internal thermal

shutdown protection mechanism.

The LM4912 is unity gain stable and may be configured with

external gain-setting resistors.

Key Specifications

n

PSRR at 217 Hz and 1kHz

65dB (typ)

n

Output Power at 1kHz with V

a16

Ω load

25mW (typ)

n

Output Power at 1kHz with V

16

Ω load

40mW (typ)

n

Shutdown Current

1.0µA (max)

n

Output Voltage change on release from Shutdown

V

Ω

1mV (max)

n

Output Noise, 20Hz to 20kHz, A-weighted

10µV (typ)

Features

n

External gain-setting capability

n

Available in space-saving MSOP package

n

Ultra low current shutdown mode

n

Mute mode allows fast turn-on (10ms) with less than

1mV change on outputs

n

2.0V - 5.5V operation

n

Ultra low noise

n

Operation at low supply voltages

Applications

n

Portable CD players

n

PDAs

n

Portable electronics devices

Typical Application

20048180

FIGURE 1. Typical Capacitive Coupled Output Configuration Circuit

June 2003

© 2003 National Semiconductor Corporation

DS200481

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