LMC1983

Digitally-Controlled Stereo Tone and Volume Circuit with

Three Selectable Stereo Inputs

General Description

The LMC1983 is a monolithic integrated circuit that provides

volume, balance, tone (bass and treble), loudness controls

and selection between three pairs of stereo inputs. These

functions are digitally controlled through a three-wire com-

munication interface. There are two digital inputs for easy in-

terface to other audio peripherals such as stereo decoders.

The LMC1983 is designed for line level input signals

(300 mV–2V) and has a maximum gain of −0.5 dB. Volume

is set at minimum and tone controls are flat when supply volt-

age is first applied.

Low noise and distortion result from using analog switches

and poly-silicon resistor networks in the signal path.

Additional tone control can be achieved using the LMC835

stereo

7-band

graphic

equalizer

connected

to

the

LMC1983’s SELECT OUT/SELECT IN external processor

loop.

Features

n Low noise and distortion

n Three pairs of stereo inputs

n Loudness compensation

n 40 position 2 dB/step volume attenuator plus mute

n Independent left and right volume controls

reduction

n External processor loop

n Signal handling suitable for compact discs

n Pop-free switching

n Serially programmable: INTERMETAL bus (IM) interface

n 6V to 12V single supply operation

n 28 Pin DIP or PLCC Package

Applications

n Stereo television

n Music reproduction systems

n Sound reinforcement systems

n Electronic music (MIDI)

n Personal computer audio control

Block Diagram

DS011279-1

August 1992

© 1999 National Semiconductor Corporation

DS011279

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