Thanks, all. Another observation is if I remove the OPT3001 from the circuit, there is no corruption of the DS1307 , no matter how many times I cycle the power.
So adding the OPT3001 is somehow affecting the DS1307 (maybe writing garbage to it) at power on or off ? On Thu, 19 Aug 2021, 19:11 Bill Gatliff, <[email protected]> wrote: > > > On Thu, Aug 19, 2021, 6:33 AM Bill Gatliff <[email protected]> wrote: > >> >> OH, ... make doubly sure the circuitry around the '1307 is right. IIRC, >> it's easy to accidentally end up with the backup battery trying to power >> the rest of your board when you pull the mains plug. That inevitably drags >> the backup voltage down to zero even if you've got a good battery. >> > > In particular, make sure your grounding and decoupling is good. If your > ground line goes missing or (has nonzero impedance during transients), that > can cause supply issues at the chip too. > > If you're powering directly from a wall-wart, unplug it from the board > instead of from the mains supply. Otherwise, the large capacitors in the > brick will slowly discharge into your circuit, causing an extended brownout. > > $0.02. > > b.g. > >>
