la3430 Sanyo Semiconductor Corporation, la3430 Datasheet - Page 7

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

(4) SNC and HCC connection circuits when coupled with the IF stage
(5) S/N improvements in region C of Fig. 1
(6) Using the HCC terminal for muting
(7) VCO damping
(8) Forced monaural
Fig. 8 shows the relation between voltages impressed on pin 7 and rates (%) of high cut (HCC). When IF meter
output voltage characteristics and region B, S/N characteristics, of Fig. 2 have been obtained, S/N improvement
by HCC can be drawn in a way similar to drawing SNC characteristics.
Fig. 2 shows typical meter outputs of a quadrature detection IF amplifier IC. (Fig. 1 shows data for the LA1140,
LA1230, and LA1231N) HCC characteristics have been designated to permit region B improvements when the IC
is directly connected to HCC (pin 7) terminal of the LA3430. The infinitesmal control currents at pin 7, similar to
pin 8, do not affect meter outputs.
Fig. 1 shows sample S/N characteristics vs. antenna inputs when SNC and HCC are connected with the IF stage
by an external circuit.
Because S/N ratios deteriorate even further in the region C of Fig. 1, it is better to improve the S/N in this region
with IF mutings. The LA1140 is available to linearly vary the IF muting. Employment of the LA3430 together
with the LA1140 further enhances S/N improvement.
Mutings in the neighborhood of 37dB are feasible by utilizing HCC functions as muting functions when used in
home stereos and no need exists to suppress treble noises. Fade-in and fade-out of mutings, permitting delightful,
shock-noise-free muting, are possible by providing a time constant to the pin 7 control.
VCO oscillations can be damped by applying a voltage not less than 7V to the HCC terminal (pin 7) to induce a
monaural mode. At this time, both SNC and HCC are in an off mode. Fig. 9 shows flow-in current by voltages
applied to pin 7.
By disconnecting LED lamp at pin 10 from VCC lamp, reception mode forced monaural function can be attained.
(Stereo lamp is turned OFF. Pilot cancel and HCC function are held.)
LA3430
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