[time-nuts] A look inside the DS3231

[Pete Stephenson]

On Sun, Jul 30, 2017, at 03:37 PM, Mark Sims wrote:
> 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.

What's the motivation for this, other than "because we can"? Aren't
existing RTC chips capable of running 10+ years from a lithium coin cell
already, to the point where the cell's self-discharge is the limiting
factor?

Is there some application where exceptionally low power use for a clock
chip would be of interest?

I ask as an interested amateur not familiar with the subtleties of such
designs.

Cheers!
-Pete