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Hitachi Semiconductor |
HD74HC221
Dual Monostable Multivibrators (with Schmitt Trigger Input)
Description
Each multivibrator features both a negative, A, and a positive, B, transition triggered input, either of which
can be used as an inhibit. Also included is a clear inpt that when taken low resets the one shot. The
HD74HC221 can be triggered on the positive transition of teh clear while A is held low and B is held high.
This device is a non-retriggerable, and therefore cannot be retriggered until the output pulse times out.
The output pulse equation is simply:
tW = 0.7·(Rext)·(Cext)
Features
• High Speed Operation
• High Output Current: Fanout of 10 LSTTL Loads
• Wide Operating Voltage: VCC = 2 to 6 V
• Low Input Current: 1 µA max
• Low Quiescent Supply Current
Function Table
Inputs
Outputs
Clear
A
B
Q
Q
LX X L H
XH X L H
XX L L H
HL
HH
LH
HD74HC221
Pin Arrangement
Logic Diagram
A
B
Clear
1A 1
1B 2
CLR1 3
1Q 4
2Q 5
Cext 2 6
2 Rext/
Cext
7
GND 8
CLR
Q
Q
QQ
CLR
(Top view)
16 VCC
15
1 Rext/
Cext
14 1 Cext
13 1Q
12 2Q
11 2CLR
10 2B
9 2A
VCC
Rext
Cext
Cext Rext
/Cext
Clear
Q
Q
Q
2
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