[time-nuts] 1 pps Sync'ing

Hal Murray hmurray at megapathdsl.net
Sun Jun 24 20:47:31 UTC 2018


> I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs to
> be aligned with the GPS 1 pps (UTC) to within 1 ns. 

That will be interesting.   You may have to get your cables and distribution 
amplifier inside the PLL.

How good is your GPS?  What's the night/day difference in GPS timing?  (after 
sawtooth correction)

What is your application?  What sort of noise/jitter/wander are you sensitive 
to and/or what can you tolerate?

One thing you can do is to derive the 10 MHz from the 100 MHz with a simple 
divide by 10.  Then run both through reclocking FFs.  If they are in the same 
package with the same clock, they will be closely aligned, but there will be 
"noise" from the 10MHz on the 100 MHz due to different loads on the power 
supply wiring.  That's probably sub ns.

Do you need your PPS to be aligned to UTC?  If not, divide down to make your 
own PPS and run it through the same reclocking.

If you do need your PPS aligned to UTC, you can PLL your PPS with the PPS from 
GPS.  The S part of PPS means that things are slow so a software/DAC solution 
will probably be appropriate.





-- 
These are my opinions.  I hate spam.






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