The scenario
A continuous 1 Hz pulse train feeds a retriggerable monostable built around a CD4538. Each valid pulse resets the timing, but if a pulse is missed the output falls to signal a watchdog timeout.
What is in this drawing
Read the decisions behind it.
01
Use a retriggerable monostable to reset timing on every input pulse
02
Include input RC coupling with diode clamp for clean edge triggering
03
Represent the CD4538 as an IC block with trigger input and output
Use for heartbeat monitoring, missing-pulse detection, or watchdog circuits where a periodic signal must be validated.
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