[time-nuts] injection locking crystal oscillator

[Dana Whitlow]

Hello Thomas,

What you ask is possible, but only if the native crystal oscillator
frequency is close enough to the signal from the GPSDO.  You
may have to tune the oscillator yourself to get it to lock, and you
may or may not find that the result is predictable from day to day.
This would depend on how much signal you inject from the GPSDO,
and other, largely imponderable factors.

I think all you can do is try it, understanding that there is also some
risk of damaging the chip if you try to inject too much in search of
success.

If you have a signal gen that you can fine tune around 10 MHz, it
would probably be worth setting it to the same output level as your
GPSDOs output and using it at first.  That way you can explore the
parameters more rapidly without (initially) bothering to retune the
oscillator on the chip.

Dana



On Thu, Feb 28, 2019 at 6:00 PM Thomas S. Knutsen <la3pna at gmail.com> wrote:

> Hello.
>
> I have a device that consists of a PLL, that has as its reference a
> 10MHz crystal.
> What I would like to do, is to inject this with 10MHz from a GPSDO,
> when that is available, and to use the internal crystal when that is
> not available.
>
> Would it be feasible to just connect it to one leg of the crystal
> oscillator with a small capacitor, and with that get injection
> locking?
> The crystal oscillator is on chip, there is a couple capacitors that
> allow for frequecy adjustments, other than that, I know nothing about
> what is on the chip. The PLL is SP5769.
>
> Br.
>
> Thomas
>
> --
> With Best regards, Thomas S. Knutsen.
>
>  Please  avoid sending  me  Word  or  PowerPoint  attachments.
>
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