Hi I think the gotcha is that the PLL (where one is involved) may be in a dynamic state a good percentage of the time. Eventually it gets close to setting and then it’s time to hop yet again. That would make the “back out” process pretty involved.
Bob > On May 15, 2019, at 1:15 PM, jimlux <[email protected]> wrote: > > Has anyone measured the details of the spread spectrum clocks used to help > meet emission limits (like FCC Part 15)? > > It seems, superficially, that they do this with some sort of deterministic > process (like a linear feedback shift register), and so, one might be able to > "back out" the (Pseudo)randomization to get better timing performance. > > > https://www.maximintegrated.com/en/app-notes/index.mvp/id/3503 > seems to indicate that they use a up/down sweep approach. > > https://www.maximintegrated.com/en/products/all-products/archive/MAX9492.html > > https://www.idt.com/products/clocks-timing/application-specific-clocks/spread-spectrum-clocks/180-01-low-emi-clock-generator > "IDT's proprietary blend of analog and digital PLL technology" > > https://www.idt.com/document/dst/idt5p50911-2-3-4-datasheet > > seems to show a triangle wave frequency modulation > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
