Integrated Circuit


MM74HC221A Dual Non-Retriggerable Monostable Multivibrator

The MM74HC221A high speed monostable multivibrators (one shots) utilize advanced silicon-gate CMOS technol- ogy. They feature speeds comparable to low power Schot- tky TTL circuitry while retaining the low power and high noise immunity characteristic of CMOS circuits.

Each multivibrator features both a negative, A, and a posi- tive, 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 MM74HC221A can be triggered on the positive transition of the clear while A is held LOW and B is held HIGH.

The MM74HC221A is a non-retriggerable, and therefore cannot be retriggered until the output pulse times out. Pulse width stability over a wide range of temperature and supply is achieved using linear CMOS techniques. The out- put pulse equation is simply: PW = (REXT) (CEXT); where PW is in seconds, R is in ohms, and C is in farads. All
inputs are protected from damage due to static discharge by diodes to VCC and ground.




  1. 74HC221 Dual Non-Retriggerable Monostable Multivibrator