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555 Timer Help

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RATabora

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Hey all,

This is my first post. Here we go!

I have about a 25ns pulse of 3.3V, that I want to delay to a 200ms pulse with a 555 timer. The problem I am having is that the 555 timer only accepts <2/3 of Vcc as a high output. I want to have anything >2/3 Vcc to give a high output. Does anyone know how to do that without introducing too many complicated parts?

Thank you!!
 

Hero999

Banned
I think a 25ns pulse is too short to trigger a 555.
 

Boncuk

New Member
Invert the +3.3V to trigger the timer at its trigger input with a low going pulse edge. Supply the timer with any voltage up to 14V to get the desired output level.
 

Hero999

Banned
Last edited:

RATabora

New Member
Wow thank you all! I will be looking into the 74LV123 for sure as it DOES seem that a 25ns pulse is too short for a 555 timer. Unfortunately I was basing the fact that it would work on a Multisim simulation.

I'll let you know how it goes! :)
 

RATabora

New Member
Hmm, it appears that the 74LV123 will be perfect for what I need. But I can't find the spice model to simulate it!

I did however find the CD4538BC Dual Precision Monostable Multivibrator in Multisim. However, the min spec on pulse width on input is 35ns, so I believe the 74LV123 would be better.
 
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