LMC1982 Datasheet, PDF (7/14 Pages) National Semiconductor (TI) – Digitally-Controlled Stereo Tone and Volume Circuit with Two Selectable Stereo Inputs

Pin Description (Continued)
Address
(A7–A0)
01000000
01000001
01000010
01000011
01000100
01000101
01000110
01000111
TABLE 1. IM Bus Programming Codes for LMC1982
Function
Input Select + Mute
Loudness, Enhanced Stereo
Bass
Treble
Left Volume
Right Volume
Mode Select
Read Digital Input 1
or
Digital Input 2
on IM Bus
Data
XXXXXX00
XXXXXX01
XXXXXX10
XXXXXX11
XXXXXX00
XXXXXX01
XXXXXX10
XXXXXX11
XXXX0000
XXXX0011
XXXX0110
XXXX1001
XXXX11XX
XXXX0000
XXXX0011
XXXX0110
XXXX1001
XXXX11XX
XX000000
XX010100
XX101XXX
XX11XXXX
XX000000
XX010100
XX101XXX
XX11XXXX
XXXXX100
XXXXX101
XXXXX11X
XXXXXXD1D0
Function
Selected
INPUT1
INPUT2
N/A
MUTE
Loudness OFF
Enhanced Stereo OFF
Loudness ON
Enhanced Stereo OFF
Loudness OFF
Enhanced Stereo ON
Loudness ON
Enhanced Stereo ON
−12 dB
−6 dB
FLAT
+6 dB
+12 dB
−12 dB
−6 dB
FLAT
+6 dB
+12 dB
0 dB
−40 dB
−80 dB
−80 dB
0 dB
−40 dB
−80 dB
−80 dB
Left Mono
Stereo
Right Mono
D0 = Digital Input 1
D1 = Digital Input 2
General Information
The LMC1982 is a CMOS/bipolar building block intended for
high fidelity audio signal processing. It is designed for line
level inputs signals (300 mV − 2V) and has a maximum gain
of −0.5 dB. While the LMC1982 is manufactured with CMOS
processing, NPN transistors are used to build low noise op
amps. The combination of CMOS switches, bipolar op amps,
and poly-silicon resistors make it possible to achieve an or-
der of magnitude quality improvement over other bipolar cir-
cuits that use analog multipliers to accomplish gain adjust-
ment. Internal circuits set the volume to minimum, tone
controls to flat, the mute to on, and all other functions off
when power is first applied. Individual left and right volume
controls are software programmed to achieve the stereo bal-
ance function. Figure 1 shows the connection diagram of a
typical LMC1982 application.
The LMC1982 has internal decoding logic that allows a mi-
croprocessor (µP) or microcontroller (µC) to communicate di-
rectly to the audio control circuitry through an INTERMETAL
(IM) Bus interface. This three-wire interface consists of a
bi-directional DATA line, a Clock (CLK) input line, and an
Identity (ID) line. Address and function selection data (8 bits)
7
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