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Pin No.
1
2
3
V
4
18
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Equivalent Internal Circuit
V CC
V CC
V CC
1
0.01
From Ceramic Sound
IF Filter at Pin 28
2
Sound Input (FM)
V CC
V CC
2.2 k
V CC
15.5 k
C4
0.0033
4
Sound De–Emphasis (FM)
V CC
V CC
100 µA
18 k
200 µA
MC44302A
PIN FUNCTION DESCRIPTION
DC Volume Control
A potentiometer of 20 kΩ or less, connected as shown, is used to
adjust the audio output level at Pin 27. There is no audio signal
Volume
10 k
present at this pin, allowing the use of unshielded wire between
Control
the IF board and the potentiometer. To prevent hum and noise
pickup, a bypass capacitor connects from this pin to ground. Refer
to Figure 17.
Sound Input (FM)
This pin is the input of the FM IF. The intercarrier sound output at
Pin 28 connects to this input through a ceramic bandpass filter.
The FM detector is active in PAL 1, PAL 2, and NTSC modes.
Refer to Table 2.
Audio Input/Audio–Video Switch
This is a multifunction input that selects the audio source that
appears at Pin 27, and the video polarity at Pins 5 and 6. Audio 1
Audio Input/
is without a dc path from Pin 3 to ground. Internally demodulated
Audio–Video
audio (AM of FM) appears at Pins 24 and 27, negative video at
Switch
Pin 5, and positive video at Pin 6. The audio source at Pin 3 is
From External
internally disconnected. Audio 2 is with the 22 kΩ resistor
Audio Source
connected. Internally demodulated audio (AM or FM) appears at
0.1
3
Pin 24, negative video at Pin 5, positive video at Pin 6, and the
27 k
audio source at Pin 3 appears at Pin 27. Video 1 is with the 3.3 kΩ
Audio 1
resistor connected. Internally demodulated audio (AM or FM)
Audio 2
appears at Pins 24 and 27, negative video at Pin 5, and positive
Video 1
video at Pin 6. Video 2 is with Pin 3 grounded. Internally
22 k
demodulated audio (AM of FM) appears at Pins 24 and 27,
positive video at Pin 5, and negative video at Pin 6. Refer to
Video 2
3.3 k
Table 1.
Sound De–Emphasis (FM)
A capacitor is connected from this pin to ground. It is used in
conjunction with internal 18 kΩ resistor to set the FM sound
de–emphasis time constant. The typical de–emphasis time
constant required for a flat audio response is 75 µs in the United
States and 50 µs in Europe. The FM sound detector frequency
response for different de–emphasis capacitor values is shown in
Figure 12.
Description
MOTOROLA ANALOG IC DEVICE DATA
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