LM4830

Two-Way Audio Amplification System

with Volume Control

General Description

The LM4830 is an integrated solution for two-way audio am-

plification. It contains a bridge-connected audio power ampli-

fier capable of delivering 1W of continuous average power to

an 8

Ω load with less than 1% THD from a 5V power supply.

It also has the capability of driving 100 mW into a

single-ended 32

Ω impedance for headset operation. There

is a 30 dB attenuator in front of a bridged power amplifier

with 6 dB of gain. The attenuation is controlled through 4 bits

of parallel digital control; 15 steps of 2 dB each.

The device also contains a microphone preamp with two se-

lectable inputs. Mic2 is selected when HS is high and A1 is in

single-ended mode. Mic1 is selected when HS is low and A1

is in bridged mode. This configuration is optimum for switch-

ing between an internal system speaker and external head-

set with microphone. The device also incorporates a buffer

used for driving capacitive loads.

The LM4830 also provides a low-current consumption shut-

down mode making it optimally suited for low-power portable

systems. In addition, the device has an internal thermal shut-

down protection mechanism.

Key Specifications

n Instantaneous peak output power:

1.4W

n Shutdown current:

0.5 µA (typ)

n Supply voltage range:

2.7V

≤ V

Features

n 4-bit digital control for 30 dB of volume attenuation

n Two selectable microphone inputs

n High performance microphone preamp

n Extra buffer for driving long cables

n No bootstrap capacitors or snubber circuits are

necessary

n Small Outline (SO) packaging

n Thermal shutdown protection circuitry

Applications

n Hands-free phone systems

n Mobile phone accessories

n Desktop conference phones

n Portable computers

n Teleconference computer applications

Connection Diagram

Dual-In-Line and

Small Outline Packages

DS012677-2

Top View

Order Number LM4830M

See NS Package Number M24B for SO

Order Number LM4830N

See NS Package Number N24A for DIP

January 1999

© 1999 National Semiconductor Corporation

DS012677

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