MC74HC4020A_01 查看數據表（PDF） - ON Semiconductor
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MC74HC4020A_01 Datasheet PDF : 8 Pages
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Clock
Reset
Q4
Q5
Q6
Q7
Q8
Q9
Q10
Q12
Q13
Q14
MC74HC4020A
12
4
8
16
32
64 128 256 512 1024 2048 4096 8192 16384
Figure 6. Timing Diagram
APPLICATIONS INFORMATION
Time–Base Generator
A 60Hz sinewave obtained through a 1.0 Megohm resistor
connected directly to a standard 120 Vac power line is
applied to the input of the MC54/74HC14A, Schmitt-trigger
inverter. The HC14A squares–up the input waveform and
feeds the HC4020A. Selecting outputs Q5, Q10, Q11, and
Q12 causes a reset every 3600 clocks. The HC20 decodes the
counter outputs, produces a single (narrow) output pulse,
and resets the binary counter. The resulting output frequency
is 1.0 pulse/minute.
VCC
VCC
120Vac
60Hz
1.0M
≥20pF
1/6 of HC14A
NOTE:
Ground MUST be isolated
by a transformer or
opto–isolator for safety
reasons.
HC4020A
13
Clock
Q5
12
Q10
10
Q11
9
Q12
1.0 Pulse/Minute
1
1/2
HC20
8
2
4
5
1/2
HC20
6
Output
Figure 7. Time–Base Generator
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