SL74HC221

System Logic

Semiconductor

SLS

Dual Monostable Multivibrator

The SL74HC221 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.

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 CLR input (positive-

edge) because of the Schmitt-trigger input; after triggering the output

maintains the MONOSTABLE state for the time period determined by

MONOSTABLE STATE. If the next trigger pulse occurs during the

MONOSTABLE period it makes the MONOSTABLE period longer.

• Outputs Directly Interface to CMOS, NMOS, and TTL

• Operating Voltage Range: 3.0 to 6.0 V

• Low Input Current: 1.0 µA

• High Noise Immunity Characteristic of CMOS Devices

ORDERING INFORMATION

SL74HC221N Plastic

SL74HC221D SOIC

° to 125° C for all packages

PIN ASSIGNMENT

LOGIC DIAGRAM

PIN 8 = GND

FUNCTION TABLE

Inputs

Outputs

Note

A

B

CLR

Q

Q

H

H

Output

Enable

X

L

H

L

*

H

*

Inhibit

H

X

H

L

*

H

*

Inhibit

L

H

Output

Enable

L

H

Output

Enable

X

X

L

L

H

Inhibit

X = don’t care

Note

state, i.e. no trigger. When the supply voltage is turned off

be some possibility of damaging the I.C. with a surge

current or latch-up. If the voltage supply filter capacitor is

automatically limited and damage the I.C. is avoided. The

maximum

forward

current

of

the

parasitic

diode

is

approximately 20 mA.