On Wednesday, 29 April 2015 14:00:17 UTC+2, Andrew Bradford wrote:
>
> You seem to be talking about the BBB, correct?
>

Correct, though it seems nearly all posts in this thread are referring to 
the BBB issue?

My initial work was on BBW back in 2012 (prior to BBB release). 
>
> It sounds like BBB has similar issues to BBW with running on battery but 
> that the issues are slightly different.
>

Well the similarity is that the regulator was being kept alive by leakage 
currents.

Your original question is actually very easy to answer: disabling 3V3A like 
you were is really really not allowed, and if leakage currents didn't keep 
it logic-high then the result would have been pulling nRESET low, game over.

Shutting down 3V3B is something you may be able to do if appropriate pad 
configuration is done (high-Z with receiver disabled, pull-up disabled, 
maybe pull-down enabled) depending a bit on the rest of the BBW schematic 
(I didn't study it in any detail), but that doesn't help you since it 
doesn't control 3V3EXP.

Bottom line: shutting down 3V3EXP on the BBW (other than in off-state or 
rtc-only sleep) is not going to happen without a hardware patch.

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