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Pin No.
10
3.0 k
2.4 k
5.1 k
11
V CC
12
V CC
13
AGC Input
20
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PIN FUNCTION DESCRIPTION (continued)
Equivalent Internal Circuit
10
Video Mode Switch
V CC
PAL 1
PAL 2
SECAM
NTSC
3.3
AFT Ouput
11
V CC
0 to 500 µA
or 2.0 mA
Digital Slew
Rate Control
AFT Mode Switch
12
V CC
V CC
24 k
5.1 k
24 k
V CC
V CC
10 k
13
To Tuner
RF AGC
Output
MC44302A
Video Mode Switch
V CC
A dc voltage at this input selects the proper video AGC and sound
demodulation technique for PAL, SECAM, and NTSC. With PAL
1 selected, AGC is keyed on the sync pulse by the horizontal PLL
which is locked to the flyback or video sync pulse present at Pin 17.
V2
The FM sound IF and detector is active. The PAL 2 selection is
identical to PAL 1 with the addition of sound muting when the
V1
acquisition circuit is unlocked or vertical sync is absent. With
SECAM selected, the video level is established by both, a long
time constant peak white detector, and a back porch keyed AGC
that corrects for transmitted black level errors while maintaining
fast AGC response. The AM sound detector is active. With NTSC
selected, AGC and sound muting is the same as in PAL 1 mode.
The FM and AM detectors are both active with the FM output at
Pin 27 and the AM output at Pin 24. Refer to Table 2.
To Tuner AFT Input.
AFT Output
I O must be externally
With detent type tuners, the automatic fine tuning output can be
limited < 4.0 mA.
used to directly control the tuner local oscillator varactor. The
varactor control input must be high impedance in order to maintain
high AFT loop gain with acceptable dynamic response. This
output has a linear sink and source current range of 0 to 500 µA,
and is digitally switched to 2.0 mA for large frequency errors. The
capacitor from Pin 11 to ground limits the bandwidth of the tuner
local oscillator loop. Digital phase–locked loop tuning systems
Variable
20
can also be controlled with the addition of a varactor diode used
Reference
to shift the PLL reference oscillator. Refer to Figures 6, 24, and 25.
Clamp Voltage
AFT Mode Switch
This input is used to activate the output of the AFT control amplifier
that appears at Pin 11, and to select the control voltage polarity
versus IF frequency. This feature allows the AFT output to work
with all types of varactor tuned local oscillators. With the AFT
Mode Switch input connected to V CC , Pin 11 is placed in a
sourcing mode when the IF carrier frequency is below nominal.
With the AFT Mode Switch input grounded, Pin 11 is placed in a
sinking mode when the IF carrier frequency is below nominal. With
the AFT Mode Switch input disconnected, Pin 11 is internally
clamped to one half of V CC , refer to Figures 6 and 25.
RF AGC Output
V CC
This output is designed to control a reverse AGC tuner. As the
antenna signal level increases, the voltage at Pin 13 decreases,
causing a gain reduction in the tuner RF stage. An external pull–up
resistor must be added if one is not provided in the tuner. Pin 13
is guaranteed to sink a minimum of 1.0 mA. Note that when
operating with a tuner that requires in excess of 5.6 V, current will
flow into Pin 13 due to conduction of the upper internal clamp
diode.
Description
MOTOROLA ANALOG IC DEVICE DATA
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