Do you mean one should use SiGe ECL (or CML) D flipflops or higher performance devices for the output synchronisers? It would surely be a little difficult to justify this given the relatively noisy outputs of most rubidium sources.
A 74HC4017 has a symmetric 1:1 mark space ratio divide by ten output. So in this respect its just as suitable as a 74XX90 for this task. Bruce [email protected] wrote: > In my opinion the best way is still to use two 74xx90 connected divide by > five and divide by two. That gives a symmetrical output. That is why you can > not > use a 390. The A output should subsequently be applied to a D or JK flip > flop with the clock input connected to the 10 MHz. The D or JK F/F should be > as > fast as what is presently still available. > Bert Kehren Miami WB5MZJ > > > In a message dated 3/30/2009 1:10:57 A.M. Eastern Daylight Time, > [email protected] writes: > > > >> What would be a "through the hole" type of IC that would have less >> jitter than a 74xx90. I CAN do surface mount if I have to. >> > > In general, I think faster logic families have lower jitter. I'm not sure > I > could prove that or find a good paper. There may be counter-examples. > > If you want low jittter, I think the right approach is to divide by X/2 and > then do the final divide by 2 in a separate chip. There are several logic > families that have only one gate or one FF in a package. They are usually > SMT, typically SP-23 type packages with fairly big pins so hand soldering > with old-fart eyes is not that hard. > > Prop time with multiple outputs in a package depends on how many outputs are > switching. In the case of a divide by 10, the pattern is stable. If you > look at the divide by 2 output pin, I'd expect more jitter since sometimes > lower order bits are switching and sometimes they are not. > > > Another approach is to use a CPLD. Clock the main divide by 10 or 100 on > the > wrong edge, and then buffer the final output on the right edge. Some CPLDs > are targeted at low power. It'd expect them to have more jitter than the > ones targeted at high-speed. There may not be much choice. > > > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
