Thanks for your reply. How does this issue damage the processor?
Jason Op woensdag 21 december 2016 14:08:47 UTC+1 schreef Gerald: > > 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] > <javascript:>> 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/msgid/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] <javascript:>. >> 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] <javascript:> > http://beagleboard.org/ > [email protected] <javascript:> > > -- 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/f4612892-76f9-4d83-bdbd-8072af11b172%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
