Would an « AVRDIV » have similar performances, with similar 8 pins processors such as the Attiny13a ? Advantage : it features one cycle instructions, so possible to divide by many other factors (including odd numbers) GC
> Le 8 janv. 2022 à 04:05, Tom Van Baak <t...@leapsecond.com> a écrit : > > All -- The 2012 test results for the T2-mini, which contains a PIC divider > chip, is here: > > http://leapsecond.com/pic/jitter/ > > It's about 1 ps, or sqrt(2) less because it was comparing two T2-mini against > each other with a common reference. Also note that this measurement is the > sum total of the Wenzel sine-to-square circuit onboard the T2mini, the PIC > divider chip itself, and the 74AC04 buffer chip. > > I also included some plots of a baseline test to show that the Wenzel ULN > (Ultra Low Noise) reference and the Miles' TimePod analyzer are not the > limiting factor in the test. > > Hal -- The pD17 PIC divider used in the T2-mini has a single output. See > T2-mini schematic in the above URL. The PIC code is here: > > http://leapsecond.com/pic/src/pd17.asm > > Bruce -- I agree with your comments. Thanks for posting that. > > Attila -- I have not measured the voltco. Note the T2-mini has an onboard > regulator. I also have not measured tempco. Although the jitter is about 1 ps > the wander over that 10 minute run is about ±6 ps (2.4 ps rms). Look at the > phase plot in the test results. This is also why the ADEV plot has that > characteristic plateau from tau 2 to 20 s. > > IIRC, the test was done causally on a floor in open air so walking, > breathing, drinking coffee, and checking email are known to wiggle things at > the picosecond level. Someone could look into this more if they wish. I would > be interested to know how much of the wandering is due to the voltage > regulator vs. Wenzel transistor circuit vs. the PIC vs. the 74AC chip. > > /tvb > > > On 1/7/2022 12:40 PM, Hal Murray wrote: >>> The two biggest outside influences on the PICDIV are supply voltage and >>> temperature. >> Another interesting influence is the number of outputs that are switching and >> the load on them. In particular, if you have several outputs running at >> different frequencies, the clock-out delay should be slightly longer when 2 >> outputs switch when compared to when only one is switching. >> >> Has anybody measured that on a PIC? (or similar chip) >> >> I think one of tvb's picDEVs has several outputs. >> > > On 1/7/2022 5:00 PM, Bruce Griffiths wrote: >> That entire thread is full of misinformation and should be ignored unless >> one understands the difference between random and data dependent jitter. >> >> For a well designed divider with a single output frequency only the random >> jitter spec is significant. >> >> One doesn't need a bunch of expensive LeCroy gear to measure RJ of such >> dividers as its PN manifestations are readily apparent and measurable. >> >> Using one of the supposedly super low jitter flipflops isn't a panacea. In >> practice unless an appropriately designed ZCD is used the wideband input >> noise of the very fast FF will dominate and produce much more jitter than >> expected due to the relatively slow slew rate of the outputs of most 10MHz >> sources. >> >> Bruce > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
