I have no plans to fix this. If you need battery operation, which the BBB does not really support as it needs 5V for the USB, then you need to modify the board design for your usage.
Gerald On Wed, Dec 21, 2016 at 7:03 AM, Jason van Belzen <[email protected]> wrote: > 3v3 regulator bug: > > https://groups.google.com/forum/#!msg/beagleboard/7sxPePT7wkM/3vFMPydR20IJ > > The issue is the interconnection of the 3v3a and 3v3b power domains, >> resulting in significant leakage current between them (e.g. via protection >> diodes) whenever one is powered while the other is not. The 3v3b -> 3v3a >> leakage was of course exactly the reason for moving the enable-signal of >> the 3v3b regulator (U4) from 3v3aux (LDO2) to 3v3a. However, while this >> resolved the issue at boot, it did not resolve it at shutdown when running >> on dc power, and made it far worse when running on battery. >> >> The problem is that when the 3v3a supply (LDO4) is disabled, the 3v3b >> regulator remains enabled until 3v3a drops below the threshold voltage of >> the enable-input of U4, which is far below 3.3V (specified to be somewhere >> between 0.4V (at 25 ͏°C) and 2V). As a result, current will start to flow >> from 3v3b to 3v3a, and apparently enough current to keep it logic-high in >> the opinion of the 3v3b-regulator (despite the ~375 ohm discharge resistor >> the PMIC applies when LDO4 is disabled!). >> >> Thus, once turned on, the 3v3b regulator manages to keep itself enabled >> indefinitely as long as it is supplied from SYS_5V. When entering >> off-state, the PMIC automatically connects SYS to battery power rather than >> DC- or USB-supply. If there's no battery, then the capacitors on SYS will >> drain pretty fast hence the 3v3b shutdown is not delayed much. If there's a >> battery, then you're pretty screwed. >> >> It is very important to note that this issue is not merely one of battery >> lifetime; this leakage current may *damage the processor*. >> >> > > Op woensdag 21 december 2016 13:55:57 UTC+1 schreef Gerald: >> >> And what is the 3.3V bug? >> >> Gerald >> >> >> On Wed, Dec 21, 2016 at 6:54 AM, Jason van Belzen <[email protected]> >> wrote: >> >>> Hi, >>> We are planning to build an IoT gateway based on a Beagle Bone Black. >>> Till now we were experimenting with the Beagle Bone Black Rev C. >>> Since we need to protect the filesystem, we want to use a battery so we >>> can detect a power failure and nicely shutdown the system. >>> >>> Unfortunaletly we encountered a problem. >>> After shutting down the system with a battery connected, the 3v3 >>> regulator bug is triggered. >>> The BeagleBone Black is a good board for our purpose, so we really want >>> to use this board. >>> >>> A few questions come up in our minds. >>> 1. How bad is this bug? Is it really gonna damage the processor? >>> 2. Are there any other solutions than patching to an unified 3v3 rail? >>> 3. Are there any next revisions planned for the BeagleBone Black? And if >>> they are planned, will this bug be fixed in the next revision? >>> >>> Thanks. >>> >>> Regards Jason >>> >>> -- >>> 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]. >>> To view this discussion on the web visit https://groups.google.com/d/ms >>> gid/beagleboard/a3dea840-c1cf-4dad-a0dc-b19ba9936504%40googlegroups.com >>> <https://groups.google.com/d/msgid/beagleboard/a3dea840-c1cf-4dad-a0dc-b19ba9936504%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> >> >> -- >> Gerald >> >> [email protected] >> http://beagleboard.org/ >> [email protected] >> >> -- > 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]. > To view this discussion on the web visit https://groups.google.com/d/ > msgid/beagleboard/bbbedc74-a881-4c4e-84f5-0897b8ea8372%40googlegroups.com > <https://groups.google.com/d/msgid/beagleboard/bbbedc74-a881-4c4e-84f5-0897b8ea8372%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- Gerald [email protected] http://beagleboard.org/ [email protected] -- 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CAHK_S%2BcosJJBtXdcnt3KuhF%2BeDUCpU49EEKRNawFZvBAeeJ2xw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
