1

2

π

C

30k / / 30k

(Hz)

C = External capacitor connected to Pin 5

275

Audio ICs

BA3430S / BA3430F / BA3430FS

FMute detection circuit

(1) Mute detection based on noise and music signals

The signals of each block in the mute detection circuit are

shown in the diagram below.

(2)

Sensitivity switch amplifier circuit

The noise level and signal frequency of the tape differ

during playback and fast forward. Therefore, this signal

amplifier includes a circuit for switching the detection fre-

quency and gain for playback and fast forward.

This circuit switches the detection frequency and gain for

playback and fast forward.

A 10k

Ω or less resistor must be connected to the input pin

to limit the input current. The electrolytic capacitor be-

tween the input pin and ground is for preventing incorrect

detection. Without this capacitor, sensitivity switch noise

may cause incorrect detection of songs.

Input switch truth table

2) Input low pass filter

High frequency noise increases during fast forward. This

filter reduces high frequency noise. It consists of an inter-

nal 30k

Ω resistor which combines the left and right equal-

izer output and an external capacitor connected to Pin 5.