LMC1992 Digitally-Controlled Stereo Tone and
Volume Circuit with Four-Channel Input Selector
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
line level input signals (300 mV
b
2V) and has a maximum
gain of 0 dB
The internal design is optimized for external capacitors hav-
ing values of 0 1
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鈥檚 select-out select-in external processor loop
Features
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Low noise and distortion
Four stereo inputs
40 volume levels including mute
20 fader levels
All attenuators have a 2 dB of attenuation per step
Front back fade control
External processor loop
Only three external components per channel
Serial programmable standard MICROWIRE
TM
interface
Single supply operation 6V to 12V supply voltage
Protection address (similar to DS8906)
DC-coupled inputs
Single supply operation
Applications
Y
Y
Y
Y
Automotive audio systems
Sound reinforcement systems
Home entertainment stereo television and music re-
production systems
Electronic music (MIDI)
Block and Connection Diagrams
TL H 10789 鈥?2
Order Number LMC1992CCN
See NS Package Number N28B
TL H 10789 鈥?1
Left channel shown Pin numbers in parentheses are for the right channel
DNR is a registered trademark of National Semiconductor Corporation
COPS
TM
and MICROWIRE
TM
are trademarks of National Semiconductor Corporation
C
1995 National Semiconductor Corporation
TL H 10789
RRD-B30M75 Printed in U S A