[time-nuts] A look inside the DS3231

Pete Stephenson pete at heypete.com
Sat Jul 29 14:32:30 EDT 2017

On Thu, Jul 27, 2017, at 09:46 PM, Trent Piepho wrote:
> Looks like it still says "DALLAS SEMICONDUCTOR" to the left of Maxim.
> Maybe Maxim only wanted to change the mask enough to find some empty
> space to sign it?

It does indeed say "DALLAS SEMICONDUCTOR".

I managed to get some high-quality photos using the microscope's
on-board camera and have updated the photo album at
https://imgur.com/a/0zudj with the newest ones (they're the
all-rectangular photos below the two circular photos). There's some
high-resolution composite images.

Some things I found interesting:
- There's a section just above the "Maxim" part that has several
snippets of text ("17A3", "16A3", etc.). In normal light, each of these
bits of text is a different color, where the colors correspond to
different layers of the chip. Each bit of text has a different depth of
focus, indicating they're physically closer or further from the lens.
Does anyone know what material the colors might correspond to?

- There's several square grids of circles-in-squares circuit elements. I
have no idea what these are.

- I find it remarkable that this circuit can operate on less than a
microamp during normal usage, including temperature conversion.

The DS3231 has on-board temperature monitoring to correct the crystal
frequency: is this something where they would have bothered putting a
separate sensor next to the crystal itself, or are the die and the
crystal are close enough and in the same package that they could use an
on-die sensor like a diode and call that "good enough"?


Pete Stephenson

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