NE555/SA555/NA555

PRECISION TIMERS

NE555/SA555/NA555

Document number: DS35112 Rev. 4 - 2

9 of 14

www.diodes.com

February 2012

© Diodes Incorporated

Missing Pulse Detector

The circuit shown in Figure 7 can be used to detect a missing pulse or abnormally long spacing between consecutive pulses

in a train of pulses. The timing interval of the monostable circuit is retriggered continuously by the input pulse train as long as

the pulse spacing is less than the timing interval. A longer pulse spacing, missing pulse, or terminated pulse train permits the

timing interval to be completed, thereby generating an output pulse as shown in Figure 8.

 

Fig. 7 Circuit for Missing Pulse Dectector

Fig. 8 Timing Waveforms for Missing Pulse

Dectector

Frequency Divider

By adjusting the length of the timing cycle, the basic circuit of Figure 1 can be made to operate as a frequency divider. Figure

9 shows a divide-by-three circuit that makes use of the fact that retriggering cannot occur during the timing cycle.

Fig. 9 Divide by Three Circuit Waveforms