LM4991

3W Audio Power Amplifier with Shutdown Mode

General Description

The LM4991 is a mono bridged audio power amplifier ca-

pable of delivering 3W of continuous average power into a

3

Ω load with less than 10% THD when powered by a 5V

power supply (Note 1). To conserve power in portable appli-

cations, the LM4991’s micropower shutdown mode (I

0.1µA, typ) is activated when V

DOWN pin.

Boomer audio power amplifiers are designed specifically to

provide high power, high fidelity audio output. They require

few external components and operate on low supply volt-

ages from 2.2V to 5.5V. Since the LM4991 does not require

output coupling capacitors, bootstrap capacitors, or snubber

networks, it is ideally suited for low-power portable systems

that require minimum volume and weight.

Additional LM4991 features include thermal shutdown pro-

tection, unity-gain stability, and external gain set.

Note 1: An LM4991LD that has been properly mounted to a circuit board will

deliver 3W into 3

Ω (at 10% THD). The other package options for the LM4991

will deliver 1.5W into 8

Ω (at 10% THD). See the Application Information

sections for further information concerning the LM4991LD and LM4991M.

Key Specifications

n

Improved PSRR at 217kHz and 1kHz

64dB (typ)

n

P

n

LM4991LD (only), 3

Ω,4Ω

3W (typ), 2.5W (typ)

n

All packages, 8

Ω load

1.5W (typ)

n

Shutdown current

0.1µA (typ)

Features

n

Available in space-saving LLP and MA packages

n

Ultra low current shutdown mode

n

Can drive capacitive loads up to 500pF

n

Improved pop & click circuitry reduces noises during

turn-on and turn-off transitions

n

2.2 - 5.5V operation

n

No output coupling capacitors, snubber networks,

bootstrap capacitors or gain-setting resistors required

n

Unity-gain stable

Applications

n

Wireless and cellular handsets

n

PDA’s

n

Portable computers

n

Desktop computers

Connection Diagrams

Small Outline Package

LLP Package

20074002

Top View

Order Number LM4991MA

See NS Package Number M08A

20074039

Top View

Order Number LM4991LD

See NS Package Number LDC08A

May 2003

© 2003 National Semiconductor Corporation

DS200740

www.national.com