[time-nuts] A look inside the DS3231

[Mark Sims]

A friend of mine is an engineer for one of the biggest manufacturers  of clock chips and has worked quite a bit on their clock chips and is quite familiar with the issues of building consistent ultra low power oscillators in a production product.   Getting nanowatt (and now sub-nanowatt) level oscillators to do their thing consistently is not easy.   Getting them to do it with customer supplied crystals is a big thing.   Variations by the crystal maker regularly cause previously working products to stop working.  Also they are notoriously sensitive to PCB layout issues.  Older, higher power clock chips don't have nearly as many problems as the newer ultra low power designs.   Competition to see who can make the lowest power clock chips seems to be one of the biggest drivers for new clock chip designs.

Oh, and although the clock chip oscillators have good long term accuracy they tend to have lots of jitter and poor ADEVs.