Mohammad The LTC6957-4 is inputs are intended to be AC coupled.
With AC coupling a variable rate pulse will experience varying switching thresholds. A constant fraction discriminator minimises timing walk when the pulse amplitude varies whilst the ristetime remains constant. If the pulse risetime also varies a more complex amplitude and risetime compensated discriminator is necessary to minimise timing walk. For minimum timing jitter there will be an optimum zero crossing detector bandwidth. Bruce > > On 26 March 2017 at 05:32 Mohammad-Hadi Sohrabi <mhsohr...@ucdavis.edu> > wrote: > > Hello, > I have been following the posts here for a while and learned alot. I > thought I could get some help as well. > I need to detect less than 20 ps between two incoming pulses from a > detector. pulses are 5ns wide and the rise time and fall time is around > 2ns > each. > I am planning to use a constant fraction discriminator, simply a fast > comparator with less than 500 MHz bandwidth for zero crossing detection > and > providing a very sharp edge. Then this can be fed into a TDC such as GPX2 > or anything of this sort. I think these can be fairly easily implemented > on > FR4. > Recently I stumbled upon LTC6957-4 logic converter from another > discussion. > Can anyone guide me if this can be used for producing a sharp edge from a > pulse that I mentioned? Datasheet suggests 0.5 ns rise time is possible > but > I think this is for single tone sine wave and not a short pulse. > > Bests, > Mohammad > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
