74LS221 Datasheet PDF

SN74LS221 Dual Monostable Multivibrators with Schmitt-Trigger Inputs Each multivibrator of the LS221 features a negative-transitiontriggered input and a positive-transition-triggered input either of which can be used as an inhibit input. Pulse triggering occurs at a voltage level and is not related to the transition time of the input pulse. Schmitt-trigger input circuitry for B input allows jitter-free triggering for inputs as slow as 1 volt / second, providing the circuit with excellent noise immunity. A high immunity to VCC noise is also provided by internal latching circuitry. Once triggered, the outputs are independent of further transitions of the inputs and are a function of the timing components. The output pulses can be terminated by the overriding clear. Input pulse width may be of any duration relative to the output pulse width. Output pulse width may be varied from 35 nanoseconds to a maximum of 70 s by choosing appropriate timing components. With Rext = 2.0 kΩ and Cext = 0, a typical output pulse of 30 nanoseconds is achieved.