Threshold
7
6
R-S
Flip Flop
1.90V
Reference
Voltage
Each
Bias
Circuit
1
2
3
Output Circuit
15
1.90V
4
GND
Reference Voltage
Current Output
Frequency Output
Timer
Comparator
Fig. 4
Operation of F/V converter circuit using this IC are as
follows.
When horizontal sync signal is input to pin 6 of IC through
QH03, this performs as a trigger, charge of capacitor CH13
which is connected to pin 5 begins. Voltage at pin 5 is
compared with reference voltage(Vcc x 2/3) by the comparater
inside IC, and the voltage finally reaches the reference
voltage to reverse the comparater. This reverse operation
discharges the capacitor rapidly. Next, when hor sync signal
comes, this operation is again repeated.
The period that this capacitor is being charged is constant, in
spite of input signal.
Hor. Sync
pulse
Voltage
of pin6
Voltage
of pin5
0
0
Current
of pin1
0
Vcc
2
3
1.9V
RH16+RH17
Tc
TH
Fig. 5
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