la3430 Sanyo Semiconductor Corporation, la3430 Datasheet - Page 5

• Manufacturer Part Number: la3430
• Description: Pll Fm Mpx Stereo Demodulator With Pilot Canceler For Car Stereo Use
• Manufacturer: Sanyo Semiconductor Corporation

Cautions when employing sample application circuits
1. Pilot cancelling circuit
2. Separation adjustments
3. SNC (stereo noise control) and HCC (high-cut control)
· Adjust separation by 10k potentiometer in low pass filter.
· Adjust R
· Adjust noise AGC by C
· Adjust pilot cancellation by 50k potentiometer connected to pin 15 of LA2110.
· Reponse speeds of pilot cancellation to follow levels can be varied by adjusting capacitance value of 1 F capacitor
· Adjusting pilot cancellation.
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.
The LA3430 has separation parameters that have been set to provide maximum separation when used in conjunction
with the LA2110, a noise-canceler IC, or the equivalent. The LA3430 by itself exhibits separation only in a 25 to 30
dB range. If a phase correction circuit is provided in the LA3430 input circuit, it can exhibit intrinsic separation
charactersitics, typically 50 dB.
The LA3430 has SNC and HCC terminals for improved S/N ratios when operating in weak radio fields. By adjusting
the SNC terminal, noises unique to stereo FM in weak fields can be reduced. The HCC terminals permits further
improvement of effective S/N ratios by lowering treble levels of FM noises in weak fields. (See Fig. 2)
STEREO deteriorates approximately 21.7 dB (compared to MONO) in weak radio feilds (Fig. 2). Generally, when
S/N ratios deteriorate below 30 to 40 dB, noises become quite noticeable. Section (1) shows ways to set SNC and
HCC when radio field strenghs are divided into 3 regions, A, B, and C, (Fig. 2). SNC is expected to function in
region A, and HCC in region B. In region C, shallow muting is effected in the IF stage.
connected across pins 11 and 12 of LA3430. Distortion factors deteriorate with reduction in value.
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 LA2110. Set their ranges for V : 200mV/div. AC, H : 20 s/
div.
Then, adjust pilot cancel control to minimize indications of valve voltmeter.
When the LA3430 alone is used (sample application circuit 1), adjust cancel control through a 19kHz B.P.F. to
minimize carrier leakage level at output pins (pins 5 and 6).
S
for noise detection sensitivity under strong to medium radio fields. Set at adequate value.
Y
and R
Y
to enhance noise suppression in medium to weak radio fields.
LA3430
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