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High accuracy clock/Freq source
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High accuracy clock/Freq source

by diracdeltafunct on Tue Jul 28, 2020 10:20 am

I was curious if anyone had any product recommendations.

Currently I have a project that is in need of a very high accuracy 10 Hz square(ish) wave source (+/-1ppm, ideally better). I already have a Rb standard in the project so if anything (microcontroller etc) can accept that as its clock input thats even better.

Happy to share some more info if needed.
Thanks

diracdeltafunct
 
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Re: High accuracy clock/Freq source

by adafruit_support_mike on Wed Jul 29, 2020 1:39 am

The DS3231 might be able to do the job:

https://www.adafruit.com/?q=DS3231

It's spec'd for +/-2ppm over the 0C to 40C temperature range, with some additional drift factors also in the 1ppm range. If you control temperature, supply voltage, and the other major sources of drift in its operating environment, it should be pretty good.

If you already have a rubidium standard, you might be able to use a simple count register, like the 74x161 or 74x163. Those are 4-bit synchronous counters, so all their output pins change at the same time, as clocked by the input. The highest bit goes high and low at 1/16th the frequency of the input, and can be used to clock another counter for another x16 division:

https://octopart.com/search?q=74x161&cu ... SD&specs=0
https://octopart.com/search?q=74x163&cu ... SD&specs=0

Cascading several chips that way will introduce some propagation lag, so the final output won't be exactly in sync with the original clock, but the offset should be reasonably constant if you control the operating conditons (stable supply voltage, lots of bypass capacitors, etc).

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Please be positive and constructive with your questions and comments.