TLH10789

December 1994

LMC1992 Digitally-Controlled Stereo Tone and Volume

Circuit with Four-Channel Input-Selector

General Description

The LMC1992 is a monolithic integrated circuit that provides

four stereo inputs bass and treble tone controls and vol-

ume balance and front-rear fader controls These functions

are digitally controlled through a three-wire communication

interface All of the LMC1992s functions are achieved with

only three external capacitors per channel It is designed for

gain of 0 dB

The internal design is optimized for external capacitors hav-

ing values of 01 mF or less This allows the use of chip

capacitors for coupling and tone control functions

Low noise and distortion result from using analog switches

and thin-film silicon-chromium resistor networks in the sig-

nal path

Volume and fader are at minimum and tone controls are flat

when supply voltage is first applied

Additional tone control can be achieved using the LMC835

stereo

7-band

graphic

equalizer

connected

to

the

LMC1992’s select-outselect-in external processor loop

Features

Y

Low noise and distortion

Y

Four stereo inputs

Y

40 volume levels including mute

Y

20 fader levels

Y

All attenuators havea2dBof attenuation per step

Y

Frontback fade control

Y

External processor loop

Y

Only three external components per channel

Y

interface

Y

Single supply operation 6V to 12V supply voltage

Y

Protection address (similar to DS8906)

Y

DC-coupled inputs

Y

Single supply operation

Applications

Y

Automotive audio systems

Y

Sound reinforcement systems

Y

Home entertainmentstereo television and music re-

production systems

Y

Electronic music (MIDI)

Block and Connection Diagrams

TLH10789 – 1

Left channel shown Pin numbers in parentheses are for the right channel

TLH10789 – 2

Order Number LMC1992CCN

See NS Package Number N28B

DNR

is a registered trademark of National Semiconductor Corporation

C1995 National Semiconductor Corporation

RRD-B30M75Printed in U S A