[time-nuts] More on SiLabs 5340

John Ackermann N8UR jra at febo.com
Mon Jan 29 15:38:33 EST 2018

I'm slowly learning how these ultra-low-jitter clock generators work. 
Yesterday I posted some phase noise results in "free run" mode where the 
48 MHz crystal on the evaluation board was the only reference.

Today I tried replacing the crystal with a 10 MHz input, and found that 
the evaluation board requires surgery to support that.  What I was able 
to do, though, was feed 10 MHz into the "Input 0" port which apparently 
disciplines the free-running crystal.  I used a 10811A fed into a 
T2-Mini with divider removed, so all it does is provide the Wenzel 
squaring circuit.  Results attached, added to the plots from yesterday. 
Also attached is an ADEV plot proving that the 10 MHz is in control.

The close-in phase noise is quite amazing, but the floor is much worse 
than in free-run mode.  This was a very hay-wire experiment, so there 
are lots of things that could be suboptimal.  It sure would be nice to 
get the best of both those plots!

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