April 1994

Revised May 1999

© 1999 Fairchild Semiconductor Corporation

DS011680.prf

www.fairchildsemi.com

74VHC221A

Dual Non-Retriggerable Monostable Multivibrator

General Description

The VHC221A is an advanced high speed CMOS

Monostable Multivibrator fabricated with silicon gate CMOS

technology. It achieves the high speed operation similar to

equivalent Bipolar Schottky TTL while maintaining the

CMOS low power dissipation. Each multivibrator features

both a negative, A, and a positive, B, transition triggered

input, either of which can be used as an inhibit input. Also

included is a clear input that when taken LOW resets the

one-shot. The VHC221A can be triggered on the positive

transition of the clear while A is held LOW and B is held

HIGH. The VHC221A is non-retriggerable, and therefore

cannot be retriggered until the output pulse times out. The

output pulse width is determined by the equation:

PW

= (Rx)(Cx); where PW is in seconds, R is in ohms,

and C is in farads.

An input protection circuit ensures that 0 to 7V can be

applied to the input pins without regard to the supply volt-

age. This device can be used to interface 5V to 3V systems

and two supply systems such as battery back up. This cir-

cuit prevents device destruction due to mismatched supply

and input voltages.

Features

s Power down protection is provided on all inputs

s Pin and function compatible with 74HC221A

Ordering Code:

Surface mount packages are also available on Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.

Logic Symbol

IEEE/IEC

Connection Diagram

Order Number

Package Number

Package Description

74VHC221AM

M16A

16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow

74VHC221ASJ

M16D

16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide

74VHC221AMTC

MTC16

16-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide

74VHC221AN

N16E

16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide