LM4910

Output Capacitor-less Stereo 35mW Headphone

Amplifier

General Description

The LM4910 is an audio power amplifier primarily designed

for headphone applications in portable device applications. It

is capable of delivering 35mW of continuous average power

toa32

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

3.3V

The LM4910 utilizes a new circuit topology that eliminates

output coupling capacitors and half-supply bypass capaci-

tors (patent pending). The LM4910 contains advanced pop &

click circuitry which eliminates noises caused by transients

that would otherwise occur during turn-on and turn-off.

Boomer audio power amplifiers were designed specifically to

provide high quality output power with a minimal amount of

external components. Since the LM4910 does not require

any output coupling capacitors, half-supply bypass capaci-

tors, or bootstrap capacitors, it is ideally suited for low-power

portable applications where minimal space and power con-

sumption are primary requirements.

The LM4910 features a low-power consumption shutdown

mode, activated by driving the shutdown pin with logic low.

Additionally, the LM4910 features an internal thermal shut-

down protection mechanism. The LM4910 is also unity-gain

stable and can be configured by external gain-setting resis-

tors.

Key Specifications

n

PSRR at f = 217Hz

65dB (typ)

n

Power Output at V

Ω, and THD ≤

1%

35mW (typ)

n

Shutdown Current

0.1µA (typ)

Features

n

Eliminates headphone amplifier output coupling

capacitors (patent pending)

n

Eliminates half-supply bypass capacitor (patent pending)

n

Advanced pop & click circuitry eliminates noises during

turn-on and turn-off

n

Ultra-low current shutdown mode

n

Unity-gain stable

n

2.2V - 5.5V operation

n

Available in space-saving MSOP, LLP, and SOIC

packages

Applications

n

Mobile Phones

n

PDAs

n

Portable eletronics devices

n

Portable MP3 players

Typical Application

20030565

FIGURE 1. Typical Audio Amplifier Application Circuit

February 2003

© 2003 National Semiconductor Corporation

DS200305

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