I ran into a similar finding on the A6 board. Interestingly, the A5C works correctly. These are with a battery connected.
I'm investigating a proper shutdown and power-off if the main 5V is removed. I have a Li-Ion battery connected to keep everything running until a proper shutdown/power-off can occur. Using the method in "Re: [beagleboard] Chip power down and PMIC_POWER_EN" while in Uboot, I can see that the A5C shuts everything down including the VDD_3V3B supply (see schematic). The A6 does not. Now if there is no battery connected, they both power-off. So what's happening? Brad On Thursday, October 25, 2012 2:23:40 PM UTC-7, Andrew Bradford wrote: > > On Thu, 25 Oct 2012 16:13:48 -0500 > Gerald Coley <[email protected] <javascript:>> wrote: > > > You are correct. This is something we just ran into yesterday and we > > are looking at a solution. The solution is being tested and will not > > be something that shows up in the near future, but hopefully soon. It > > MAY be something that could be done with a wire mod, but it is too > > early to tell. Should know more by Monday. > > Thanks! So I'm not crazy, that's good to know. :) > Even if the wire mod is complex, it'd be great if you could share it. > > > > On Thu, Oct 25, 2012 at 4:07 PM, Andrew Bradford < > > [email protected] <javascript:>> wrote: > > > > > If I disable LDO3 in the TPS65217, VDD_3V3A should turn off. > > > VDD_3V3A turning off should disable U8 linear regulator causing > > > VDD_3V3EXP to turn off. > > > > > > It doesn't. > > > > > > Disabling LDO3 in the TPS65217 causes VDD_3V3A to drop to > > > approximately 2.4 V. This is not low enough to disable the U8 > > > linear regulator's enable pin. Further, disabling LDO4 after this > > > only causes VDD_3V3A to drop to approximately 1.2 V. Again, this > > > is not enough to disable U8 linear regulator's enable pin. > > > > > > I've tested on an A3 and an A6 bone. > > > > > > I realize there's grave impacts to disabling LDO3 or LDO4, ie: much > > > of the board won't work any more although the ARM core and DDR will > > > still be operating. That's OK for my experiments. > > > > > > How can I turn off VDD_3V3EXP from software without completely > > > turning off all rails on the TPS65217? Is it possible? > > > > > > I'm trying to do this in order to debug an issue we see with a > > > custom cape at power down when running on 3.7 V lithium battery. > > > With our cape attached, VDD_3V3EXP latches on even when the rest of > > > the BeagleBone is powered off. This is due to SYS_5V staying > > > present due to the battery and U8 linear regulator not powering > > > down before the latch action occurs. The TPS65217 and AM3359 are > > > both in the proper states, I can boot due to power button press > > > once in the OFF state (defined by the TPS65217 data sheet). But > > > keeping VDD_3V3EXP running will ruin the battery life while in the > > > OFF state. > > > > > > On the cape, we pull up to VDD_3V3EXP for things like MMC/SD and > > > I2C. I believe this is part of the problem as there may be power > > > back feeding through the pull-ups enough to cause the latch > > > situation. But we believe we're following the recommended pull-up > > > strategy documented in the Bone SRM. > > > > > > Has any one else seen issues like this when attempting to enter the > > > TPS65217 OFF state with capes attached that use pull-ups to > > > VDD_3V3EXP while running on 3.7 V lithium battery power? If so, > > > what capes work? > > > > > > Yes, I realize this is quite a corner case. Sadly, it's an > > > important one for me. > > > > > > Thanks, > > > Andrew > > > > > > -- > > > > > > > > > > > > > > > -- 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/groups/opt_out.
