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Pin No.
14
Video IF
AGC Filter
0.1
15
V CC
6.2 k
1.0 k
4.3 k
16
MOTOROLA ANALOG IC DEVICE DATA
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PIN FUNCTION DESCRIPTION (continued)
Equivalent Internal Circuit
V CC
V CC
14
V CC
V CC
RF AGC
Delay
15
0.01
Internal
IF AGC
V CC
V CC
0.4 mA
0.4 mA
Horizontal PLL Filter
16
0.68
1.5 k
0.05
MC44302A
Video IF AGC Filter
A capacitor connects from this pin to ground to control the video
IF AGC rate of change with respect to a change in input signal
level. An increase in input signal level causes an increase in the
voltage at Pin 14 which controls the internal AGC action. Pin 14
has an unsymmetrical source and sink current of 150 µA and 8.0 µA
respectively. The AGC filter voltage versus IF differential input
signal level is shown in Figure 1.
2.0 V
Horizontal
Gating
RF AGC Delay
A voltage applied to this input sets the video IF signal level
threshold before gain reduction of the tuner begins. The threshold
setting is tuner dependent but is usually in the range of 1.0 mV to
2.0 mV of signal at the antenna. Too low of a setting will cause
premature tuner gain reduction and a poor picture and sound
signal to noise ratio, while too high of a setting will cause tuner
overload and picture distortion. The IF differential input signal
level versus RF AGC takeover threshold is shown in Figure 2.
From Pin 14
AGC Filter
Voltage
Horizontal PLL Filter
This is a dual function pin. With the network shown, the horizontal
phase–locked loop oscillator provides a keying pulse to properly
gate the AGC when in PAL, SECAM, and NTSC modes. With
Pin 16 grounded, both the AM and FM sound IF and detectors are
inhibited. By placing Pin 3 in the Audio 2 mode, the variable audio
output at Pin 27 is active and can be used to control the level of
the externally processed digital sound. Refer to the description of
Pin 3.
Description
21
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