LA1781M_09 Datasheet, PDF (10/48 Pages) Sanyo Semicon Device – For Car Radios Single-Chip Tuner IC

Continued from preceding page.
Pin No.
Pin function
24
AM/FM signal meter
32
Dedicated FM signal meter
LA1781M
Pin description
Fixed-current drive signal meter
output.
In AM mode, pin 32 outputs a
1mA current. Thus the HCC
circuit is turned off.
26
Stereo indicator for the SD pin The voltage V23 switches between
three modes as follows.
FM reception :
5V : The SD pin operates linked
to the IF counter buffer.
2.5V : Forced SD mode: operates
as the SD pin.
0.7V : Reception mode: stereo
indicator
AM reception : (two modes : 0 and 5V)
5V : Operates as the seek SD pin.
0V : Reception mode. Not used.
27
MRC control voltage time
constant
The MRC detector time constant is
determined by a 100Ω resistor and C2
when discharging and by the 2μA
current and C2 when charging.
Equivalent circuit
VCC
FM
S-meter
AM
S-meter
AM/FM
SW
32
10kΩ
24
10kΩ
Outputs a 1-mA
current during AM
reception
MRC
AM/FM
SW
AM/FM Stereo
SD
indicator
Seek/stop
switching
26
100kΩ
VDD
VCC
2μA
VCC
C2
27
100Ω
Pin 28
28
SNC control input
The sub-output is controlled by a 0 to
1V input.
VREF
28
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