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LA1784M Datasheet, PDF (12/50 Pages) Sanyo Semicon Device – Single-Chip Tuner IC for Car Radios | |||
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Continued from preceding page.
Pin No.
Function
30
Noise canceller input
31
AM/FM detector output
LA1784M
Description
Pin 30 is the noise canceller input.
The input impedance is 50 kâ¦.
Pin 31 is the AM and FM detector
output
In FM mode, this is a low-
impedance output.
In AM mode, the output
impedance is 10 kâ¦.
To improve the low band
separation, use a coupling
capacitor of over 10 µF.
Equivalent circuit
VCC
FM
detector
output
31
10 kâ¦
VCC
AM
detector
1 µF
+
30
Noise
canceller
50 kâ¦
4.2 V
VCC
A11730
FM S-meter output block
MRC AC input block
32
IF S-meter output and MRC
DC input
Adjust the external 1-k⦠resistor
to attenuate the MRC AC input
and control the circuit.
33
Mute drive output
â¢The muting time constant is
determined by an external RC
circuit as described below.
Attack time: TA = 10 k⦠à C1
Release time: TR = 50 k⦠à C1
â¢Noise convergence adjustment
The noise convergence can be
adjusted when there is no input
signal by inserting a resistor
between pin 33 and ground.
â¢Muting off function
Ground pin 33 through a 4-kâ¦
resistor.
10 kâ¦
32
+
1 µF
1 kâ¦
MRC input
C1
+
0.1 µF
A11731
SEEK
OFF
VCC
33
50 kâ¦
10 kâ¦
MUTE
AMP.
SOFT HOLE Band
MUTE DET muting
50 kâ¦
SD circuit
A11732
Continued on next page.
No. 6039-12/50
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