About SN74AHC123 datasheet page-10, Is tMIR require spec more than tMIR = 0.3 × tw, correct?
For example, tw: 500ms ⇒ tMIR: 150ms.
In that case, input frequency is less than 6.6Hz required, is it correct?
I think that it is very restricted.
Best regards,
Satoshi
Hello Satoshi-san,
The tMIR is relative to the pulse width of the output due to the way that these devices work.
So in this case, yes you are correct that to retrigger the 500ms output, the retriggering signal would have to come at least 150ms later to ensure that the output is retriggered to extend the pulse width beyond 500ms. Retriggering is shown in the image below for reference.
As for your comment about 6.6Hz, I don't understand specifically how this is restrictive? Are you concerned that your retriggering could happen earlier and you want to ensure that the time is extended further?
For example the retriggering could happen 50ms later and you want to ensure that the tw is 550ms instead of 500ms? What is the application?
Please help me to understand what exactly your concern might be and I would be happy to help try to alleviate the issues that you foresee in the design.
Best,
Michael
