LA1787M Datasheet, PDF (36/54 Pages) Sanyo Semicon Device – Single-Chip Tuner IC for Car Radios

LA1787M
Unique Features of the LA1784M Hall Detection Circuit (1) Fig.27
2 _{When the tuner is moved in 50 kHz steps.}
With a 51 kΩ resistor between pins 37 and 34.
f1
ANT
1 With the SD sensitivity adjusted to be 20 dBµ.
f2
IN
0
Unique Features of the LA1784M Hall Detection Circuit (2) Fig.28
2 _{When the tuner is moved in 50 kHz steps.}
With a 51 kΩ resistor between pins 37 and 34.
With the SD sensitivity adjusted to be 20 dBµ.
1
0
–1
–1
6
6
4
4
2
2
0
0
6
6
4
4
2
2
0
f2 = 97.9 MHz, 120 dBµ
0
fm = 400 Hz, 22.5 kHz dev.
f2 = 97.9 MHz, 40 dBµ
8
f1 = 98.1 MHz, 120 dBµ
8
fm = 1 kHz, 22. 5kHz dev.
fm = 400 Hz, 22.5 kHz dev.
f1 = 98.1 MHz, 40 dBµ
fm = 1 kHz, 22.5 kHz dev.
6
6
4
4
2
2
0
97.7
97.8
97.9
98.0
98.1
98.2
98.3
Frequency, fr — MHz
0
97.7
97.8
97.9
98.0
98.1
98.2
98.3
Frequency, fr — MHz
• Notes on the quadrature input level
When a strong field is being received the quadrature signal input (pin 36) requires a 200 mV rms input, and the
detection transformer and the damping resistor between pins 36 and 37 must be designed.
(We recommend the Sumida SA-208 transformer and a 10 kΩ resistor between pins 36 and 37.)
When the pin 36 input level falls below 160 mV rms, the Hall detection circuit operates and the pin 33 mute drive
output voltage increases. Therefore, when pin 36 input is from 160 to under 200 mV rms during strong field
reception, the muting circuit may or may not operate due to sample-to-sample variations between individual ICs.
Furthermore, the SD function may not operate, and the audio output level may be reduced. Incorrect operation due
to sample-to-sample variations and temperature characteristics can be prevented by keeping the pin 36 voltage at
200 mVrms or higher.
Pin 33 VMute — QD Input Level
6
With pins 34 and 37 shorted.
With 5 V applied to pin 24.
5
Fig.29
SA208 + LA1787M IF Input Characteristics Fig.30
4 0.8
3 0.6
4
3
2
75 Ω
75 Ω
+
0.022 µF
SG
1
10.7 MHz
36
37 _LA1888M
0
92
94
96
98
100
102
104
106
QD input level — dBµ
2 0.4
1 0.2
THD 1 kHz
75 kHz dev
–100 –80 –60 –40 –20 0
–120
20 40 60 80 100 120
∆f — kHz
With the resistor between _–0.2
pins 36 and 37 open.
∆f=0→
With a 10 kΩ resistor
–0.4
10.7 MHz
between pins 36 and 37.
–0.6 _{Voltage between pins 37 and 34}
–0.8 ^{(referenced to the pin 37 voltage)}
No. 6655-36/54