LMC1992CCN National Semiconductor, LMC1992CCN Datasheet - Page 8

• Manufacturer Part Number: LMC1992CCN
• Description: IC CTRLR DGTL STEREO 4CHAN 28DIP
• Manufacturer: National Semiconductor
• Type: Tone and Volume Controlr

Specifications of LMC1992CCN

• Applications: Audio Systems
• Mounting Type: Through Hole
• Package / Case: *
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *LMC1992CCN

3 utilizes the external loop to include DNR and a multi-band
Applications Information
The SELECT OUT pins (8 and 22) enable greater system
design flexibility by providing a means to implement an ex-
ternal processing loop This loop can be used for noise re-
duction circuits such as DNR (LM1894) or mulit-band graph-
ic equalizers (LMC835) It is important to ensure that if both
are used the noise reduction circuitry precede the equaliza-
tion circuits Failure to do so will result in improper operation
of the noise reduction circuits The system shown in Figure
equalizer
AUDIO MUTE
A mute function with attenuation of 100 dB is possible with
the volume control set to
code set to 01000XX0000 (open circuit)
TONE CONTROL RESPONSE
Base and treble tone controls are included in the LMC1992
The tone controls use just two external capacitors for each
stereo channel Each has a corner frequency determined by
the value of C2 and C3 (Figure 4) and internal resistors in
the feedback loop of the internal tone amplifier The maxi-
mum amplitude boost or cut is determined by the data sent
to the LMC1992 (see Table I)
Reduction (LM1894) and Equalizer (LMC835) (One Channel Only LMC1992)
FIGURE 3 System Block Diagram Showing Inclusion of DNR Noise
b
80 dB and the INPUT select
(Continued)
8
The typical tone control response shown in the Typical Per-
formance Curves were generated with C2
0 0082
modifying the tone control response it is important to note
that the ratio of C3 and C2 sets the mid-frequency gain
Symmetrical tone response is achieved when C2
However with C2
‘‘flat’’ the frequency response will be flat at 20 Hz and 20
kHz and
The frequency where a tone control begins to deviate from
a flat response will be referred to as the turn-over frequen-
cy With C
frequency is nominally
The base turn-over frequency is nominally
when maximum boost is chosen The inflection points (the
frequencies where the boost or cut is within 3 dB of the final
value) are for treble and bass
F and show the response for each step When
a
6 dB at 1 kHz
e
C2
e
f
f
e
f
BI
TT
BT
f
TI
e
C3 the LMC1992’s treble turn-over
2(C3) and the tone controls set to
e
e
e
2 C(164 1 k )
2 C(14 2 k )
2 C(27 7 k )
2 C(2 3 k )
1
1
1
1
TL H 10789 – 19
e
C3
e
C3
e