LA1787M Datasheet, PDF (37/54 Pages) Sanyo Semicon Device – Single-Chip Tuner IC for Car Radios

LA1787M
R_36-37
Open
10 kΩ
Detector output Pin 36 AC level
MPX OUT
Vo
QDIN
330 mVrms
235 mVrms
280 mVrms
200 mVrms
• Band Muting Adjustment Procedure
The muting bandwidth can be modified as shown in figure 31 with the resistor R_BW between pin 34 and 37.
R_BW — Muting Bandwidth
Fig.31
280
RBW
240
+
+
1 µF
0.47 µF
200
SA208
10 kΩ
Sumida
37 36 35 34
160
ANT IN 98 MHz 100 dBµ
120
80
40
0
1.0
2 3 5 7 ₁₀
2 3 5 7 ₁₀₀
2
Resistor RBW between pins 34 and 37 — kΩ
3. AM
• AM AGC system
The LA1787M RF AGC circuit takes its input from three sources: the WIDE AGC pin (pin 46), the MIDDLE
AGC pin (pin 49) and NARROW AGC. There is also an IF AGC circuit.
RW
1st MIX 10.7MHz CF
2nd MIX 450kHz CF
IF Amp.
DET
RF
62
49
52
31
1st OSC
X'tal
46
Middle AGC IN
Wide AGC IN
ANT
damping
RF AGC
Narrow AGC IN
Amp.
IF AGC
VCC
42
240 kΩ
VCC
44
2.2 µF
57
+
47 µF
48
+
3.3 µF
Fig. 32
A11762
No. 6655-37/54