Retriggerable one-shot timing — extending pulse width with a second trigger A retriggerable monostable has nominal pulse width 10 ms. It is triggered, and 3 ms later another trigger arrives. What is the resulting total output pulse width (in ms)?

Introduction / Context:
Retriggerable one-shots (retriggerable monostables) produce an output pulse of fixed nominal width T after each valid trigger. If a new trigger arrives while the output is still active, the timing interval restarts, effectively extending the pulse. Understanding this behavior is important for pulse stretching and missing-pulse detection.

Given Data / Assumptions:

• Nominal width T = 10 ms per trigger.
• First trigger at t = 0 ms; second trigger at t = 3 ms.
• Device is retriggerable (new triggers restart the timing window).

Concept / Approach:
For a retriggerable device, the output stays high for T after the most recent trigger. Each time a new trigger arrives during the active pulse, the expiration time becomes (time of latest trigger + T).

Step-by-Step Solution:
Initial trigger at 0 ms starts a 10 ms pulse, scheduled to end at 10 ms.Second trigger at 3 ms restarts timing; new planned end time = 3 ms + 10 ms = 13 ms.No further triggers occur; therefore, the total high time since t = 0 ms is 13 ms.Hence, the resulting pulse width is 13 ms.

Verification / Alternative check:
Draw a time line: high from 0–13 ms with a restart at 3 ms; waveform matches vendor timing diagrams for retriggerable monostables (e.g., 74HC123).

Why Other Options Are Wrong:
3 and 7 ms confuse remaining time vs. total. 10 ms ignores the retrigger. Only 13 ms reflects the restart behavior.

Common Pitfalls:
Mixing retriggerable with non-retriggerable behavior; forgetting that the second trigger must meet minimum pulse width and re-arm conditions.

Final Answer:
13