Thanks for the advice, guys. I actually had a couple of relays attached to this without flyback diodes, so that may be causing voltage spikes on the 5V input line.
I'll take a look at the un-loaded startup of my regulator tomorrow and see how it looks. The regulator portion of the schematic is: [image: Inline image 2] Best, Morgan On Fri, Dec 11, 2015 at 9:15 PM, Graham <[email protected]> wrote: > Morgan: > > It is likely a transient voltage spike that can come out of your switcher. > > The BBB does not turn on it's power supply until it thinks the incoming > voltage is stable, which means that your 12V to 5V switcher is starting up > without a load. If it overshoots badly in that start-up period, it could > kill something. Or if it overshoots when the BBB load is finally applied > > I would start by repetitively starting up your 12V to 5V switcher, without > a load on it, and watching what the output does on a storage (memory) > oscilloscope, so that you can see the worst case startup condition. Then > repetitively add a load equal to the BBB and all its input capacitance, and > watch what happens. > > What were you controlling with the BBB/Cape? Things like relays or > stepper motors generate inductive spikes that can easily kill > semiconductors, if the spikes are not managed correctly. > > --- Graham > > == > > > On Friday, December 11, 2015 at 7:14:38 PM UTC-6, Morgan Redfield wrote: >> >> I think I managed to burn out the TPS65217 on the BBB using a custom cape >> that I designed. The cape has a DCDC switching regulator that I'm using to >> drop a 12V supply down to 5V for the beagle bone. I have the 5V from that >> switching regulator connected to pins P9.6 and P9.5. >> >> I've now had two BBBs fail while powering them from the board. I left >> both on for a couple of days, and at some point the BBB just died. After >> that, the BBB don't boot at all, even with the cape unplugged. >> >> When I apply 5V from a benchtop supply to P9.6, I only see 1.1V on P9.7 >> (system 5V). >> If I hit the power button (S3), then the voltage on P9.7 will jump up to >> around 2.5V before falling back to 1.1V over around 20s. >> >> I'm not sure what's going on here, since the power supply I'm using looks >> pretty clean to me. It's an average of 5.14V with max 150mVpp noise. It's >> rated to 2A current draw. Switching frequency is 150kHz. >> >> Does anyone have any idea what might be happening here? Any ideas about >> what I should try next? >> >> Thanks, >> Morgan >> > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/hpHmvGR3cGU/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
