LA1787M Datasheet, PDF (10/54 Pages) Sanyo Semicon Device – Single-Chip Tuner IC for Car Radios

LA1787M
Continued from preceding page.
Pin No.
Function
Description
This pin functions both as the IF
counter buffer (AC output) and as
the seek/stop switch pin.
The voltage V23 switches
between the following three
modes.
IF counter buffer seek/stop
During FM reception:
23
switching
5 V: Seek mode
2.5 V: Forced SD mode
0 V: Reception mode
AM reception
(two modes: 0 and 5 V)
5 V: Seek mode
0 V: Reception mode
4.9V
+
–
SW
+
–
SD
Equivalent circuit
50kΩ
10kΩ
AM MUTE
1.3V _{VCC IF counter}
buffer
150Ω
50F
23
51kΩ
IF
BUFF.
STOP
Forced SEEK
SD: 2.5V 5V
A13568
VCC
24
AM/FM signal meter
Fixed-current drive signal meter
output
In AM mode, pin 32 outputs a
32
Dedicated FM signal meter
1-mA current. Thus the HCC
circuit is turned off.
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
A13569
The voltage V23 switches
between three modes as follows.
FM reception:
5 V: The SD pin operates linked
to the IF counter buffer.
2.5 V: Forced SD mode: operates
26
Stereo indicator for the SD pin
as the SD pin.
0.7 V: Reception mode: stereo
indicator
AM reception: (two modes: 0 and 5 V)
5 V: Operates as the seek SD pin.
0 V: Reception mode. Not used.
AM/FM Stereo
SD
indicator
Seek/stop
switching
26
100kΩ
VDD
A13570
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