Overview
The LA75691 is a PAL/NTSC multichannel audio VIF/SIF signal-processing IC that makes the minimum number of adjustments possible. The system is designed so that VCO adjustment makes AFT adjustment unnecessary, thus simplifying the adjustment steps in endproduct manufacturing. PLL detection is adopted in the FM detector, allowing the LA75691 to support multichannel detection for the audio signal. In addition, it also incorporates a buzz canceller that suppresses Nyquist buzz for improved audio quality.

FEATUREs
• Excellent buzz and buzz/beating characteristics provided by a PLL detection technique that includes a buzz canceller.
• The second IF AGC filter is built in.
• No coils are used in the AFT and SIF circuits, making them adjustment free.

Functions
[VIF Block]
    • PLL detector with minimum number of adjustments
    • AFT
    • Equalizer amplifier
    • RF AGC
[First SIF BLOCK]
    • First SIF detector
    • HPF
[SIF Block]
    • PLL-based FM detector
[Muting Block]
    • AV muting