TECHNICAL DATA
IN74HC221A
Dual Monostable Multivibrator
The IN74HC221A is identical in pinout to the LS/ALS221. The device
inputs are compatible with standard CMOS outputs; with pullup resistors,
they are compatible with LS/ALSTTL outputs.
N SUFFIX
PLASTIC
There are two trigger inputs, A INPUT (negative edge) and
B INPUT (positive edge). These inputs are valid for rising/falling signals
The device may also be triggered by using the RESET input (positive-
edge) because of the Schmitt-trigger input; after triggering the output
maintains the MONOSTABLE state for the time period determined by the
external resistor REXT and capacitor CEXT. Taking RESET low breaks this
MONOSTABLE STATE. If the next trigger pulse occurs during the
MONOSTABLE period it makes the MONOSTABLE period longer.
16
1
D SUFFIX
SOIC
16
1
ORDERING INFORMATION
IN74HC221AN Plastic
IN74HC221AD SOIC
•
•
•
•
Outputs Directly Interface to CMOS, NMOS, and TTL
Operating Voltage Range: 3.0 to 6.0 V
Low Input Current: 1.0 µA
TA = -55° to 125° C for all packages
High Noise Immunity Characteristic of CMOS Devices
PIN ASSIGNMENT
LOGIC DIAGRAM
1A
1B
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
CC
1REXT/CEXT
1CEXT
1RESET
1Q
DEXT
REXT
DEXT
1Q
CEXT
CEXT
REXT
2Q
2Q
2CEXT
2RESET
2REXT/CEXT
GND
2B
2A
FUNCTION TABLE
PIN 16 =VCC
PIN 8 = GND
Inputs
Outputs
Note
A
B
H
RESET
H
Q
Q
Note
(1) CEXT, REXT, DEXT are external components.
(2) DEXT is a clamping diode.
Output
Enable
The external capacitor is charged to VCC in the stand-by
state, i.e. no trigger. When the supply voltage is turned off
CX is discharged mainly through an internal parasitic diode.
If CX is sufficiently large and VCC decreases rapidy, there
will be some possibility of damaging the I.C. with a surge
current or latch-up. If the voltage supply filter capacitor is
large enough and VCC decrease slowly, the surge current is
automatically limited and damage the I.C. is avoided. The
maximum forward current of the parasitic diode is
approximately 20 mA.
X
H
L
L
H
H
H
L *
L *
H *
H *
Inhibit
Inhibit
X
Output
Enable
L
H
X
Output
Enable
X
L
L
H
Inhibit
X = don’t care
* - except for monostable period
Rev. 00
IKSEMICON [ IK SEMICON CO., LTD ]
