I'm DFAE. I have a question about Unit of Long-Term Drift specification.
The unit of Long-Term Drift is ppm/√kHr according to the datasheet of LTC6655. What's the meading of ppm/√kHr? Is it ppm/31.6hr?
I wouldn't take it as that. Lets just take 20ppm/√kHr of the LS8 package as an example, if we compute for the drift @3000 hour, we can compute it like this:
(20ppm/√kHr ) * √3kHr = 34ppm
which also can be seen at figure 10b. Also if we ever change it, it will only go as 0.63ppm/√Hr. The square root of time only signifies that the effect of LTD will be lesser and lesser as the time goes by.