[time-nuts] crystal (or MEMS) oscillators with low hysteresis

[Bob Camp]

Hi

I'm guessing that power is also an issue, so cheap OCXO's are out. If that's
true, I believe you are already at the "cheap vs good" inflection point with
the cell phone TCXO. At < $2 they are pretty tough to beat. Just the fancy
crystal in something better is going to give you a big boost in the price. 

Bob 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jim Lux
Sent: Friday, September 07, 2012 11:36 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] crystal (or MEMS) oscillators with low hysteresis

Consulting the hive-mind here on the list..

If one were looking for small/cheap/mass produced oscillators which have 
decent phase noise..  what kind has the most repeatable frequency vs 
temperature curve.



The usual 1ppm TCXO has about 0.1 ppm hysteresis, while other less 
"stable" oscillators may have bigger variation with temperature 
(>1ppm/degree C isn't a problem) but be more repeatable (perhaps the 
kind that they use as a thermometer?)

And, then, are those available in an inexpensive mass produced form 
(e.g. the precision quartz thermometer is NOT inexpensive or mass produced)

Phase noise need (not a hard requirement) is not a big driver
-45 @ 1 Hz
-75 @ 10 Hz
-105 @ 100 Hz
-130 @ 1 kHz
-145 floor out to 15 MHz

The parts I use now are actually about 10 dB better than that (-58 at 1 
Hz, -90 @ 10 Hz, -117 at 100 Hz, and floor of -153)


Ideally, I'd like to find something that has zero hysteresis.. BUT, if 
there is an equation that can predict the hysteresis by knowing the 
temperature history, that would probably work (although that has a bunch 
of problems... what about temperature changes when power is off)



This isn't a spec that typically shows up in the mass produced XO 
catalog: they focus more on bounding the frequency error over some range 
of environments .. good to within 50 ppm from 10-55 C or something like 
that.  So I'm looking for practical experience.

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