[time-nuts] Multiple Time Interval Counters to measure Transients?

[Florian Teply]

Hello,

Am Sat, 8 Sep 2012 19:41:28 +0200 (CEST)
schrieb Marek Peca <marek at duch.cz>:

> > (..) But then I'll have to throw a few hundred Time Interval
> > Counters at the problem in order to get the information on the
> > duration of the transients.  So in general, amplitude  information
> > comes from the comparator trigger levels, time information from the
> > TICs.
> >
> > What I expect from the DUTs is transients in the range between 1 and
> > maybe 50 nanoseconds duration, but on some circuits they may be a
> > lot quicker as the bipolars are wicked fast (about 3-5 ps gate
> > delay in ECL inverters).
> >
> > What do you guys think, would a truckload of TICs do the job? Maybe
> > not on the Bipolars, but at the plain CMOS this should do.
> 
> 
> It depends on how much precise you need the TICs (TDCs) to be. If it
> may be around +-100ps..1ns, the solution is simple enough and some
> hundreds of channels are feasible.
> 
Well, for the CMOS stuff 100ps should do just fine. Of course, less
is better, but there's only so much one can reasonably do for so many
channels... Even a PICTIC should be able to do better than 500 ps for 
a single channel. From what I've read, a few hundred units of HP5370
should solve the problem as well, but then there's only so much space...

> If you need units of ps, the challenge is big, IMHO. Currently, we
> are testing our Time-to-Digit Converter within single FPGA, out last
> design exhibited 7ps RMS of accuracy. In case you were interested, I
> expect finishing of demo board during October. It would be more
> FPGA-resources consuming, though.
>
I'd be very much interested. 7ps to me seems to be even more than I'd
need for the CMOS stuff. Just out of curiosity: Does this work already
from 0ps on or is the minimum count higher than that? And what's the
limiting factor to accuracy you experience with your current design? Is
it actually the FPGA and its properties or something else?

Best regards,
Florian