[time-nuts] trimble Thunderbolt, how to get 25 or 27 mHz from it??

Attila Kinali attila at kinali.ch
Mon Jan 8 09:12:07 EST 2018


On Mon, 8 Jan 2018 13:14:16 +0000
Chris Wilson <chris at chriswilson.tv> wrote:

> Thanks for the very fast reply! Would it be possible to use one of
> these frequency multiplier IC's? Sounds simpler, but maybe there are
> down sides?
> 
> http://uk.farnell.com/on-semiconductor/nb3n502dg/pll-clock-multiplier-8soic/dp/2101849

Bruce's idea is much lower noise. The NB3N502 datasheet states
an typical output jitter of 15ps. That's HUGE for a normal VCXO
output that is usually below 1ps. The low-noise OCXOs have something
in the order of 100fs. Alternatively, you can use something like
an ADF4002 and an VCXO with 25/27MHz. That should give you a much
better performance, mostly limited by the VCXO. But you will need
to have a sine-to-square conversion of the 10MHz output of the
Thunderbolt first, as the ADF4002 has a slew-rate limit on its
reference input.

BTW: stay away from any VCXO that mentiones "programable" in its datasheet.
These are XO + fractional PLL combinations where the PLL allows quick
and cheap realization of odd frequencies. But their spurs and noise floor
is much worse than normal XOs.

			Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson



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