LA3375 Datasheet, PDF (4/11 Pages) Sanyo Semicon Device – Pilot Cancel-Provided PLL FM MPX Demodulator for Car Stereos

LA3375
Cautions when employing sample application circuits
1) Adjust separation by 10kΩ potentiometer in low pass filter.
2) Adjust R_S for noise detection sensitivity under strong to medium radio fields. Set at appropriate value.
3) Adjust noise AGC by C_Y and R_Y to enhance noise suppression in medium to weak radio fields.
4) Adjust pilot cancellation by 50kΩ potentiometer connected to pin 15 of LA2110.
5) Reponse speeds of pilot cancellation to follow levels can be varied by adjusting capacitance value of 1µF capacitor
connected across pins 11 and 12 of LA3375. Distortion factors deteriorate with reduction in value.
6) Adjusting pilot cancellation.
For example consider the sample application circuit 2. Assume the input signal consists only of pilot signals. First
connect an oscilloscope and a valve voltmeter to pin 2 of the LA2110. Set their ranges for V : 200mV/div. AC, H :
20µs/div.
When oscilloscope waveform is
turn pilot cancel control to change it to the following :
Then, adjust pilot cancel control to minimize indications of valve voltmeter.
When the LA3375 alone is used (sample application circuit 1), adjust cancel control through a 19kHz BPF to
minimize carrier leakage level at output pins (pins 5 and 6).
*Refer to the LA2110 catalog for LA3375/LA2110 applications and characteristics.
1. Pilot cancelling circuit
A level-following type has been used. Once set, it can easily accommodate varying pilot modulation depths among
stations. Cancelling signal is a sawtooth wave obtained by integrating a square wave that is proportionate in ampli-
tude to pilot level with C and R.
2. Separation adjustments
The LA3375 has separation parameters that have been set to provide maximum separation when used in conjunction
with the LA2210, a noise-canceler IC, or the equivalent. The LA3375 by itself exhibits separation only in a 25 to 30
dB range. If a phase correction circuit is provided in the LA3375 input circuit, it can exhibit intrinsic separation
charactersitics, typically 50 dB.
3. Adjusting the free running frequency
Use a timing set resistor and a semi-set resistor, when connecting a frequency counter. Connect the counter with a
high impedance input to the connection between these resistors with a 100-kΩ resistor, as shown below.
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