[time-nuts] ACAM GP22 Chip

Attila Kinali attila at kinali.ch
Wed Nov 25 18:46:25 EST 2015

On Wed, 25 Nov 2015 14:19:37 -0000
"Thomas Allgeier" <th.allgeier at gmail.com> wrote:

> It is not that I don't trust ACAM (we are one of their customers) but from 
> the source I am measuring I get a lot of what you guys probably call jitter. 
> So I want to be sure the jitter comes from the oscillator I am measuring and 
> not from the GP22.
> Absolute accuracy is not the problem here, unless the 32768 Hz clock on the 
> eval board actually drifts. 

Oh.. there is one thing i forgot to mention: 32kHz oscillators are usually
optimized for low power. Modern 32kHz oscillators can get below 1uA current
consumption. This optimization for power has of course consequences, one
of them is that these oscillators are fairly noisy. People using 32kHz
oscillators usually don't care as they use these to count seconds anyways,
where the instability is dominated by the temperature coefficient of the
crystall and noise mostly averages out. I wouldn't expect the noise to
be in the ns range, but i wouldn't surprised if it was a few 10ps.
I have never done any measurements though, and I don't think i've
ever seen any jitter measurements for 32kHz oscillators, so take
this value as rough guestimate.

				Attila Kinali

Reading can seriously damage your ignorance.
		-- unknown

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