LA1781M_09 Datasheet, PDF (32/48 Pages) Sanyo Semicon Device – For Car Radios Single-Chip Tuner IC

LA1781M
Unique Featuers of the LA1781M Hall Detection circuit (1) Fig. 27
2
When the tuner is moved in 50kHz steps.
With a 51kΩ resistor between pins 37 and 34. ^f1
ANT
1 With the SD sensitivity adjusted to be 20dBμ.
f2
IN
0
Unique Featuers of the LA1781M Hall Detection circuit (2) Fig. 28
2
When the tuner is moved in 50kHz steps.
With a 51kΩ resistor between pins 37 and 34.
1 With the SD sensitivity adjusted to be 20dBμ.
0
--1
--1
6
6
4
4
2
2
0
0
6
6
4
4
2
2
0
f2 = 97.9MHz, 120dBμ
0
f2 = 97.9MHz, 40dBμ
fm = 400Hz, 22.5kHz dev.
fm = 400Hz, 22.5kHz dev.
8
f1 = 98.1MHz, 120dBμ
fm = 1kHz, 22.5kHz dev.
8
f1 = 98.1MHz, 40dBμ
fm = 1kHz, 22.5kHz dev.
6
6
4
4
2
0
97.7
97.8
97.9
98.0
98.1
98.2
98.3
Frequency, fr -- MHz
2
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 200mVrms 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 10kΩ resistor between pins 36 and 37.)
When the pin 36 input level falls below 160mVrms, the Hall detection circuit operates and the pin 33 mute drive
output voltage increases. Therefore, when pin 36 input is from 160 to under 200mV 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
200mVrms or higher.
Pin 33 VMute -- QD Input Level
6
With pins 34 and 37 shorted.
With 5V applied to pin 24.
5
Fig. 29
4
3
2
75Ω
75Ω
+
0.022μF
SG
1
10.7MHz
36
37 _LA1888M
0
92
94
96
98
100
102
104
106
QD input level -- dBμ
SA208 + LA1781M IF Input Characteristics Fig. 30
4 0.8
3 0.6
2 0.4
1 0.2
THD 1kHz
75kHz dev
--100 --80 --60 --40 --20 0
20 40 60 80 100 120
--120
Δf -- kHz
With the resistorbetween
pins 36 and 37 open.
--0.2
Δf = 0 →
With a 10kΩ resistor
--0.4
between pins 36 and 37
10.7kHz
--0.6
Voltage between pins 37 and 34
--0.8 ^{(referenced to the pin 37 voltage)}
No.6038-32/48