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:
t
W
= 0.7(Rext)(Cext)
Features
High Speed Operation
High Output Current: Fanout of 10 LSTTL Loads
Wide Operating Voltage: V
CC
= 2 to 6 V
Low Input Current: 1 A max
Low Quiescent Supply Current
Function Table
Inputs
Outputs
Clear
A
B
Q
Q
L
X
X
L
H
X
H
X
L
H
X
X
L
L
H
H
L
H
H
L
H
HD74HC221
4
AC Characteristics (C
L
= 50 pF, Input t
r
= t
f
= 6 ns)
Ta = 25
C
Ta = 40 to
+85
C
Item
Symbol
V
CC
(V) Min Typ Max Min
Max
Unit
Test Conditions
Trigger
t
PLH
2.0
--
--
210 --
265
ns
A, B or Clear to Q
propagation delay
4.5
--
--
42
--
53
time
6.0
--
--
36
--
45
t
PHL
2.0
--
--
240 --
300
ns
A, B or Clear to
Q
4.5
--
--
48
--
60
6.0
--
--
41
--
51
Propagation delay t
PHL
2.0
--
--
170 --
215
ns
Clear to Q
time
4.5
--
--
34
--
43
6.0
--
--
29
--
37
t
PLH
2.0
--
--
180 --
225
ns
Clear to
Q
4.5
--
--
36
--
45
6.0
--
--
31
--
38
Pulse width
t
w
2.0
80
--
--
100
--
ns
A, B, Clear
4.5
16
--
--
20
--
6.0
14
--
--
17
--
Minimum output
t
WQ (min)
2.0
--
1.5
--
--
--
s
Cext = 28 pF
Rext = 6 k
pulse width
4.5
--
450 --
--
--
ns
Rext = 2 k
6.0
--
380 --
--
--
Output pulse width t
WQ
4.5
0.63 0.7
0.77 --
--
ms
Cext = 0.1
F
Rext = 10 k
Output rise/fall
t
TLH
2.0
--
--
75
--
95
ns
time
t
THL
4.5
--
--
15
--
19
6.0
--
--
13
--
16
Input capacitance
Cin
--
--
5
10
--
10
pF
Caution in use:
In order to prevent any malfunctions due to noise, connect a high-frequency performance
capacitor between V
CC
and GND, and keep the wiring between the external components
and Cext, Rext/Cext pins as short as possible.