[time-nuts] PLL behavior

Azelio Boriani azelio.boriani at screen.it
Tue Sep 18 16:15:13 UTC 2012


Usually in a regular PLL the missing reference should pull the output at
the lowest voltage: as if the input frequency is too high. It helps if the
charge pump output can be disabled when the reference stops: in this case
the output voltage will go down following the droop of the
integrator/filter.

On Tue, Sep 18, 2012 at 5:39 PM, Don Latham <djl at montana.com> wrote:

> won't it depend almost entirely on the charge pump filter?
> Don
>
> Jim Lux
> > I'm looking for info on behavior of a PLL (with VCXO) when the reference
> > comes and goes periodically. When the reference is gone, the PLL will
> > "flywheel" according to whatever the loop filter does. (we can turn off
> > the "input" to the filter, so we're not trying to track noise)..
> >
> > What I'm particularly interested in is the behavior in the PLL when the
> > reference returns.
> >
> > The overall situation is where we are trying to make a frequency/phase
> > measurement over 10-100 seconds, where the reference has a 50% duty
> > cycle, and is on for a second, off for a second.
> >
> >
> > I can fairly simply model this, or just try it, but I'm looking for some
> > references to an analytical approach.
> >
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at febo.com
> > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
>
>
> --
> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> De Erroribus Medicorum, R. Bacon, 13th century.
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
>
>
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> www.lightningforensics.com
> www.sixmilesystems.com
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>


More information about the time-nuts mailing list