Voltage hysteresis measurement procedure

Question

Voltage reference datasheets specify output voltage hysteresis by certain temperature cycle. 
 My questions are 
 1. What is the temperature curve used for testing Vref? - lets say 25&deg;C to 125&deg;C to 25&deg;C (half cycle) 
 - What is the ramp rate from 25->125 
 - How log must stay at 125? 
 - what is the ramp-down rate 125-> 25 
 - how long must stay back at 25C before taking measurement. 
 2. Is there an industrial standard defining the test procedure for voltage hysteresis? 
 
 I did caracterization of few voltage references. Results shows that they srongly depend on temerature curve - e.g. - tests 25->70->25 - gives anything between 2...90 ppm. I wonder how AD tests it and is numbers cross comparable between deferent manufacurers. 
 
 Best Regards, 
 Mirtcho

BrendanWhelan · Accepted Answer

There is no standard definition, which is why ADI gives so much information in the datasheet. In particular, the mean is not very useful without deviation data. As a rule, we try to emulate a real-world temperature excursion case, such that the part will tend to soak at a given temp extreme, rather than a thermal-shock, where soak tome is limited. We change temp fairly quickly, but soak on the order of 1 hour at any temp point. This has shown to give more repeatable results and smaller deviation vs. shorter soak times.)

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Voltage hysteresis measurement procedure