[sdiy] measuring pulse width with ns accuracy...

[Bert Schiettecatte]

Hi Julien,

I tried a regular OR gate (74hc32???) and it seemed to work only 
from 3ns up to 9ns (spice simulation in orcad). beyond 9ns 
the output remained high all the time, so I suspect this is because
of the propagation delay. i'm looking at a NC7SZ32 from fairchild now,
an OR gate with 4.1ns worst case propagation delay. Maybe this will work? 

I'm also trying to figure out how to delay a signal in phase by 3ns 
for example, for testing purposes.. or how to make a variable phase delay 
that works from 3ns to 10ns ... :-)

thanks,
bert

-----Original Message-----
From: Julien Heurtebize [mailto:julien.heurtebize at tiscali.fr]
Sent: maandag 21 april 2003 0:47
To: Bert Schiettecatte
Subject: Re: [sdiy] measuring pulse width with ns accuracy...


Hi Bert
Well, in my opinion, the propagation delay in logic device is too important
to mesure your signal
phase difference...
Sorry, I don't have any ideas for the moment...
:'(

Best Regards,
Julien.

----- Original Message -----
From: "Bert Schiettecatte" <bert.schiettecatte at esat.kuleuven.ac.be>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Monday, April 21, 2003 12:36 AM
Subject: [sdiy] measuring pulse width with ns accuracy...


> hi all,
>
> i'm trying to find a way to measure phase difference
> between 2 clock signals. They have a phase difference
> anywhere between 3ns and 10ns. I thought about OR-ing
> these 2 signals and then using the result to charge
> a capacitor. I could then measure the voltage across
> the cap. Does anybody here have any idea if this will
> work? If yes, are there certain recommendations you could
> give me concerning what OR gate to use (I suppose the
> one with the shortest propagation delay I can find...)
> and what capacitor type and size?
>
> Thanks,
> bert
>