SN54LS221J

The LS221 multivibrator has two types of trigger inputs: a negative-transition-triggered input and a positive-transition-triggered input.

The output pulse width in the LS2 multivibrator is determined by the formula tW = RextCextIn2, as long as Rext and Cext are within their minimum and maximum values and the duty cycle is less than 50%. The pulse width is essentially independent of VCC and temperature variations, with output pulse widths varying typically no more than ±0.5% from device to device. If the duty cycle rises above 50%, the output pulse width will become shorter. Varying the duty cycle between low and high values causes the output pulse width to vary in length or jitter. To reduce jitter, Rext should be as large as possible, with jitter being independent of Cext. With Rext = 100K, jitter is not appreciable until the duty cycle approaches 90%. Pulse width stability is achieved through internal compensation and is virtually independent of VCC and temperature. Pulse width can be varied by choosing appropriate timing components, with output rise and fall times being independent of pulse length.

The Schmitt-trigger input circuitry for the B input provides noise immunity by allowing jitter-free triggering for inputs as slow as 1 volt/second .