On 20 May 2015 at 13:55, Maximiliano O. Sonnaillon <msonnail...@gmail.com> wrote:
> I was considering that one because it's a 3.3V logic signal. PGOOD is a > 1.8V signal and the EN pin of U4 has a minimum of 2V to consider it high. Ick, I completely overlooked that. So it seems there's no single simple solution... my cape (it's actually more like a motherboard). Same here, that's actually why we can get away with removing U4 and tying 3v3a and 3v3b together: power-hungry stuff on our board is supplied separately anyway. Perhaps the same could work in your case? LDO4 is rated for 400 mA, about half of which can be consumed by eMMC + ethernet, which leaves about 200 mA for basically just communication between the BBB and the cape. This is really a quick back-of-envelope estimate which will need more careful analysis of course. Having a unified 3.3V supply on the BBB really does make things a lot easier. If your cape uses the same supply (or one that tracks its voltage) for its IO drivers towards the BBB, the problem of current flowing through protection diodes due to uneven 3.3V supplies during power-up/down should be solved entirely. You can ignore PGOOD and reset signals in that case. The reason I'm investigating these PMIC details is that I'm using a custom > BBB for am industrial application, and we had a couple boards (BBB and > custom one) fail. I recently found warnings in new BBBs to avoid "damage in > the board".https://groups.google.com/forum/#!topic/beaglebone/CKuTbHepHYE I'm investigating the PMIC details basically to avoid similar things happening to us ;-) Especially since there's no way in hell our end-users are going to perform clean shutdowns. The quirky PMIC and the power supply structure of the BBB are both headache-inducing material. When I find a moment I'll be sure to post some observations on shutdown behaviour in that thread. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
