Brown-out conditions are handled quite robustly by many devices including many micro-controllers and at least some of the PMICs that I've used in other systems.... but apparently not the one used on the BBB.
The particular behavior about which I posted is not related to "graceful shutdown" but rather to coming back up when power returns. The TPS65217 part will apparently never re-enable its outputs after a brownout ...no matter how long the valid input voltage persists. There are a number of mitigation approaches which all require additional external circuitry but don't need additional backup power sources. Cheers, Jim On Wed, Apr 30, 2014 at 7:47 AM, Ulf Samuelsson <[email protected]>wrote: > So you generate a Brown-Out condition, which means that you operate the > part outside the spec. > Dont expect to get any electronic to work after you enter Brown-Out... > Once Brown-Out occurs, you typically have to recover by totally removing > power > until you are below certain thresholds which are chip dependent. > This can take a number of seconds. > > To protect agaist Brown-Out you need a backup battery (or a SuperCap) and > electronics > which shuts down the Beaglebone gracefully and keps the Beaglebone off > power until > nomal power is restored. > > Best Regards > Ulf Samuelsson > > > 28 apr 2014 kl. 16:39 skrev James Littlefield <[email protected]>: > > Hi Jay, > > I think this was covered in my original post.... > > "I'm working on a project using the BBB. Supplying +5V (up to 3A) > directly to the pins on P9 from a quality bench supply. I've found *that > briefly switching the +5V supply OFF and then back on* can pretty > reliably leave the BBB in an odd state characterized by... > a) No LEDs on > b) Very little current drawn from supply (10mA or less) > c) +5 present on P9.5 and P9.6 > d) 0.687V on P9.7 and P9.8 ( should be SYS_5V ). > e) P9.9 = 3.57V > f) P9.10 = 0V" > > The command line is not involved. > > I was using a lab supply and just switching it off for about 500ms then > back on. I have also been able to cause the problem using an adjustable > output supply by lowering the input voltage to around 2V then going back up > to 5V. > > Regards, > Jim > > > > > On Fri, Apr 25, 2014 at 7:58 PM, <[email protected]> wrote: > >> I just foolishly posted pretty much the same question... >> >> I'm seeing very similar behavior, I also noticed that it can still be >> powered from the USB when in this state but not VDD_5V. >> >> Can you please elaborate on the brownouts that you're seeing. You said >> they're occurring when "the power is switched off", is this in software, >> i.e. "shutdown -h now"? I haven't been able to see this on my scope but I >> also can't reliably recreate the situation in which it occurs. >> >> I know the PMICs are the same on RevA and RevB, but I believe I've only >> seen this on RevB boards. >> >> Thanks! >> jay >> >> >> On Monday, November 18, 2013 5:00:55 PM UTC-8, James Littlefield wrote: >>> >>> New to BBB but experienced with embedded systems. >>> >>> I'm working on a project using the BBB. Supplying +5V (up to 3A) >>> directly to the pins on P9 from a quality bench supply. I've found that >>> briefly switching the +5V supply OFF and then back on can pretty reliably >>> leave the BBB in an odd state characterized by... >>> a) No LEDs on >>> b) Very little current drawn from supply (10mA or less) >>> c) +5 present on P9.5 and P9.6 >>> d) 0.687V on P9.7 and P9.8 ( should be SYS_5V ). >>> e) P9.9 = 3.57V >>> f) P9.10 = 0V >>> >>> I've found that once the system is in this mode no amount of >>> pressing/holding the momentary BBB pushbuttons will get the system working >>> again. Removing input power, waiting 10 sec or so, then restoring power >>> will get things working again. >>> >>> Has anyone else seen this? It seems sort of like an issue with >>> the TPS65217C chip but I've not found any reported errata on that part. >>> >>> Thanks >>> Jim >>> >>> >>> -- >> 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/p0CwsGzNYNw/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 a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/p0CwsGzNYNw/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 a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/p0CwsGzNYNw/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. 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