Does a voltage reference continue drifting not powered?
What led to this question? Have you had problems in the past w/ a particular reference?
Do you want to build a product that has some stability requirement over a one month or
on year or ???
While developing an uncertainty budget for a new product, need to include stability drift of the voltage reference. Our calibration period is two years. The specification for the reference states, appropriately, x ppm/1000 hours. Hence, to comprehend the two years, that is 17,520 hours. Most unlikely the instrument will be on 24/7 for two years. Hence, my question: how shall the vref be quantified if not powered, as well as powered, in that period? Do voltage references continue do drift, as a square root of time, in not energized?
The short answer is yes, but the magnitude can vary depending on the mechanism. If it is an epoxy
package, the package stress will gradually relax over a period of years. Smaller packages have
more stress. We started doing a die overcoat years ago to reduce this effect. A ceramic DIP
or metal can package is the best for this. If it is loose ions in the lattice,
they will also move with time. But one effect that you can probabably observe in your lab today, is
simply to turn the digital voltmeter off and then back on after a few minutes. This can be a shift of
10 ppm or more. Talking to one of the engineers at a BIG test equipment company, he said his
HPnnnn has not been turned off in eight years. I'll ask one of the reference guys to comment
The semiconductor physics and mechanics at work? Interesting. Thank you.
I checked with the apps engineer for references, and he said some competitor's parts will shift/jump
if you turn them off and then turn them on a few minutes later. We looked at our newest family, the ADR4525 et al,
and the shift was in the noise, i.e., we couldn't tell if it was shift or a measurement error.
I forgot to mention the seminal overview article by Paul Rako. Make sure you read the comments.
Both Agilent and Fluke age the reference for 60 days before shipping......
Voltage references hold steady | EDN
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