Barry,
Yes, indeed you'll need a lot of gates to provide a 1us tpd.

Alan,
Your method crossed my mind too, but I didn't expect it would work
with a 20kHz PWM signal. I will at least need an antiparallel diode
across the resistor of the RC to let the capacitor discharge
immediately at low state of the PWM signal. Else, the delayed pulse on
the output of the AND gate will have the same delay at turnoff too. Or
am I missing something here?

Thanks!

Daniel...

----- Original Message -----
From: Barry Gershenfeld <barry@ZMICRO.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, August 30, 2001 19:26
Subject: Re: [EE]: Creating 1us pulse delay in hardware


> >>It may be possible to create this by using the propagation
> >>delay of a logic gate(s). e.g. using an AND gate, simply
>  ...
> >The trouble is that he only needs the delay in the turn-on
direction, it
> >will need to turn off immediately.
>
> Well the other problem is that gates provide delays of a few ns, so
> you would need to string a LOT of them together to get up to
> a microsecond.  But I suspect the RC delay as suggested is quite
> good enough since the rise time of something like that is
> fast enough not to be noise sensitive or require a schmitt-trigger
> (though you could throw one in for good measure).
>
> If that one-direction thing is true, that can be solved with
> another gate (or with Alan's method, for minimum parts count).
>
> Barry
>
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