Electronics > Metrology

MAX6226 voltage reference

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dietert1:
After three months of operation one could try correlation plots of each channel agains temperature in order to derive a TC, e.g. for the last data taking period. The resulting TC values will contain a common contribution from the DVM you use. If you then plot the residuals after numerically subtracting the average TC effect for each reference, unexpected changes will be much easier to pin down. I'd guess all your references together can make a sub-ppm voltage standard.

Regards, Dieter

exe:
My friends, on the latest plot I missed that ic1 went nuts. This is weird. I only see the jump correlates with drop of humidity. May be hermetic sealing is broken or something... Idk, 8 ppm sudden change is very suspicions, considering other references don't behave like that.

b_force:
Bit of an older topic, but I was just looking for some kind of affordable voltage reference myself.
There doesn't seem to be a whole lot of information shared about these things unfortunately. :(

I would still like to add some important points to the discussion, especially on the first couple of comments.
It all depends if you're looking for the best possible vs worst case scenario.

Unless I can really specify something, I would go for the last one.
Looking at the long term stability, this will eventually lead to say something like 15-20ppm or so.
Which is an equivalent of 0.002%.
Some devices seem to have an asymptote here, while others just seem to drift forever?

So instead of trying to bring that number down, one can also just use that number as a starting point.
Everything less will be just better in performance.
Obviously it depends on your application, but 0.022% total error is pretty good or very good in most cases.

Although there are two questions from my side;

1 - It seems a little unclear what they sometimes mean by the max accuracy?

According to this article; https://e2e.ti.com/blogs_/archives/b/precisionhub/posts/ic-long-term-stability-the-only-constant-is-change
They see it the rated accuracy as the max accuracy after x many years (see end of the article). While others sometimes seem to use this term as the initial value?
So in the case of the MAX6226, this 0.02% is worst case after many years.

2 - I assume that the long-term stability rating counts for when the device is powered on? Or is there also some natural drifting, even when the device is not being used at all? Certain epoxies and other bonds age over time as well for example.

exe:
Hi b_force!

Designing around worst-case scenario is a safe bet, but more often than not leads to unsatisfying guaranteed performance. This is why I made this experiment - to check what I can get in practice. As of ageing, its a good question. I contacted their support for that.

Andreas:

--- Quote from: exe on April 18, 2022, 09:47:06 am --- As of ageing, its a good question. I contacted their support for that.

--- End quote ---

Hello,

please let us know if you get a better/more detailed answer than the typical 11 ppm/1000hrs from the data sheet.

But keep in mind: this ageing drift is done under lab conditions (25 deg C constant over time).
So practically you might have different conditions.
An in my ageing experiment I see sometimes sudden drift steps which I cannot explain.

with best regards

Andreas

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