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I need to create a shorter pulse based on a trigger signal. Trigger signal has a duration between 1 to 10 ms and the desired output should be 0.5 ms.

To do the opposite (longer output pulse than input trigger) one can use a 555 as monostable (shown on the left) but what I need is the situation shown on the right. Is it possible to this with a 555 or with other monolitic IC?

enter image description here

Many thanks in advance!

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  • \$\begingroup\$ With a 555, your option is limited to adding a differentiator on the input. Otherwise you're looking for an edge triggered, non-retriggerable (74xx123 etc) as in teh answers. \$\endgroup\$ Apr 28, 2020 at 11:42

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If I understand your application correctly you can use an edge-triggered monostable multivibrator, for example 74LVC1G123.

As shown in the TI datasheet, figure 2, it is possible to have an output pulse shorter than the input pulse:

enter image description here

If the timing jitter (delay from the input to output) isn't too critical, you could also consider using a tiny microcontroller.

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  • \$\begingroup\$ Hi Photon, thanks for your answer but I read the datasheet of the 74LVC1G123 and there it says "the output pulse length only has to be longer than the longest individual bounce" so the output length is longer than the input. I need an generate an output shorter than the input \$\endgroup\$
    – Ken Grimes
    Apr 28, 2020 at 0:27
  • \$\begingroup\$ @KenGrimes, that is referring to the debouncing application. The "bounce" is when the input is de-asserted and then asserted again. Not the duration when the input is asserted. See my edit for where they explicitly show an output pulse narrower than the input pulse. \$\endgroup\$
    – The Photon
    Apr 28, 2020 at 0:33
  • \$\begingroup\$ Oh OK thanks, that looks useful! \$\endgroup\$
    – Ken Grimes
    Apr 28, 2020 at 1:11
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You could use a Monostable Pulse Generator like the LTC6993, which generates a programmable pulse width of 1 us to 33.6 s, which covers the 500 us that you need. Check pages 12 and 13 of the datasheet to program the pulse width.

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When you pass the button trigger through a capacitor, and pull it up on both sides like this, you can quite easily generate a short pulse. enter image description here enter image description here This way, when the button (red) is low for a longer time, the trigger level (green) will pull up instantly. This results in a short pulse and a desired output (blue). Of course, values should be changed when the timings are different.

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