ba3430f ROHM Co. Ltd., ba3430f Datasheet - Page 7

• Manufacturer Part Number: ba3430f
• Description: Stereo Pre-amplifiers With Mute Detection Circuits For Car Stereos
• Manufacturer: ROHM Co. Ltd.

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)
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.
(1) Sensitivity switch circuit
This circuit switches the detection frequency and gain for
playback and fast forward.
A 10k 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.
Audio ICs
Sensitivity switch amplifier circuit
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 resistor which combines the left and right equal-
izer output and an external capacitor connected to Pin 5.
The cutoff frequency of the low pass filter f
f
H
=
2
BA3430S / BA3430F / BA3430FS
C = External capacitor connected to Pin 5
C 30k / / 30k
1
(Hz)
H
is
275