LA1781M_09 Datasheet, PDF (16/48 Pages) Sanyo Semicon Device – For Car Radios Single-Chip Tuner IC

Continued from preceding page.
Pin No.
Pin function
54
Mixer output : 130μA
49
Mixer input
LA1781M
Pin description
The mixer coil connected to the pin 54
mixer output must be wired to VCC
(pin 40).
The pin 49 mixer input
Impedance is 330Ω
Pin 40 VCC
Equivalent circuit
Pin 40 VCC
54
OSC
49
330Ω
55
W-AGC IN
AM SD ADJ
58
N-AGC IN
Muting attenuation
adjustment pin
59, 60
63, 64
Mixer output
Mixer input
Pins 55 and 58 include built-in DC cut
capacitors.
The AGC on level is determined by
the values of the capacitors C1 and
C2.
Pin 55 functions as the SD sensitivity
adjustment pin in AM mode.
The output current I55 is 50μA, and
V55 varies depending on the value of
the external resistor.
The SD function operates by
comparing V55 with the S-meter
voltage.
Double balanced mixer.
Pins 59 and 60 are the mixer
10.7MHz output
Pins 63 and 64 are the mixer input.
This is an emitter insertion type
circuit, and the amount of insertion is
determined by the capacitors C1 and
C2.
Note :The lines for pins 63 and 64
must be kept separated from
the lines for pins 59 and 60.
Pin 62
VCC
W-AGC
N-AGC
55
C1
30pF
50pF
MIX ₅₈
IN
C2
MIX
OUT
50μA
AM SD
Signal meter
1ST.IF
OSC
59
60
30Ω
VCC
C1
63
5pF
RF AMP ^C2
64
5pF
VCC
620Ω
620Ω
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