Hey Lub, On Tue, 2017-02-28 at 04:19 -0800, Lyubcho Haralanov wrote: > The question that really bugs me is: why toggling LDO4 doesn't affect > the board but toggling LDO3 kills it...
I was wondering the same thing, but it could be very well because it has a different circuitry behind it inside thee AXP209. LDO3 is separate, LDO4 is shared with LDO2. >From my measurements it does seem that the AXP209 may have a small glitch however. I do not see 200 mA inrush currents, 190-ish, which is close yes, but I did not expect shutdown. Also the interrupt never fires. Not that there's anything we can do about that however... > > On Tuesday, February 28, 2017 at 10:43:08 AM UTC+2, Olliver Schinagl > wrote: > > Hey Lub, > > > > On 28-02-17 07:43, Lyubcho Haralanov wrote: > > > It seems like what Marcus suggested (turning off LDO3, setting > > voltage > > > to minimum 0.7V, then turning on LDO3 and then increasing the > > voltage to > > > 2.8V) works fine with the LIME2: > > > > > > i2c mw 0x34 0x12 0x1f > > > i2c mw 0x34 0x29 0x00 > > > i2c mw 0x34 0x12 0x5f > > > i2c mw 0x34 0x29 0x58 > > > > Yeah, I ran the same tests and even 0x7f (3.6V) 'works fine'. The > > only > > problem herein is, that this solution can't be simply rolled out to > > all > > boards I think. (All meaning the CHIP, cubieboard etc). For one, > > it > > would change current behavior of boards that are not broken. > > > > But more importantly, how does electronics behave that get this > > (fast) > > ramp up, rather than instant on power? Are there people using LDO3 > > with > > the assumption power is immediately available? > > > > So I think this alternate behavior should live behind a toggle, > > which is > > enabled for all boards that need it. (Currently all Olimex > > boards?) > > > > Olliver > > > > > > > > I'm yet to test the other designs. Nothing is final at the moment > > since > > > we are still testing, but probably the future hardware revisions > > would > > > have 4.7 uF on LDO3 and LDO4 instead of 10 uF (LDO1 is always on, > > LDO2 > > > is connected to the memory and turning it off naturally kills the > > board). > > > > > > On Monday, February 27, 2017 at 9:11:18 PM UTC+2, oliver wrote: > > > > > > Hey Lub > > > > > > On , Lyubcho Haralanov wrote: > > > > Hi, > > > > > > > > VR1 is not assembled (NA). It is not placed. Only pads are > > > provided in > > > > case you don't want to power the camera from the AXP209 > > but > > > > externally, in which case you should place VR1 and > > disconnect the SMT > > > > jumper LDO3_2.8V_E. > > > > > > > > By original design the camera is powered only by the > > AXP209. > > > > > > > > Best regards, > > > > Lub > > > > > > Thanks for the explanation of the EVB :) > > > > > > Can you also elaborate on the 10 uF for all designs however? > > > > > > Some extra information, I ran some current tests on the LDO3 > > > power-up/shutdown and while 200 mA max sourcing current is > > never > > > reached, the chip does shut down before the max voltage has > > been > > > reached. For example setting ldo3 to max ( i2c mw 0x34 0x29 > > 0x7f ) we > > > get screenshot 3v6.png where we can see the max voltage is > > only 2.32. > > > > > > Repeating the same test however with 2.3 V ( i2c mw 0x34 0x29 > > 0x40 ) > > > yields 2V3.png, which also causes an AXP209 failure. This > > supprised > > > me a > > > little, as I expected the 2.3V to actually work, as that is > > the voltage > > > we failed before. Also failure happens sooner and max current > > is lower. > > > > > > After some trial and error, we find that 1.95 V, in this > > case, still > > > works, but that I suppose really depends on the capacitance, > > but by no > > > means reliably! > > > > > > Due to the small timebase (50 uS) we cannot clearly see the > > power rail > > > dropping, but be assured, for the 2V3 and 3V6, power slowly > > drops as > > > capacitors discharge. > > > > > > > > > While this can and should be solved in hardware (smaller > > capacitor) > > > there's hundreds of thousands of boards in the wild with > > this > > > configuration and thus a software solution is needed. > > > > > > The AXP209 does have slew rate control, however this does not > > apply > > > when > > > toggling the LDO3 output switch. What I thus propose, is a > > quirk-flag, > > > for buggy boards, where we set the minimal voltage, enable > > power and > > > than set the desired voltage, letting the internal slew rate > > control > > > slowly ramp up voltage. > > > > > > > > > > > > What I still would love to hear from you guys, is why this > > could be > > > happening. The spec-sheet does say 200 mA of sourcing > > capability. > > > But it > > > seems this is not exactly true? At least not when toggling > > LDO3 via > > > reg12 for sure. > > > > > > Olliver > > > > > > > > > > > On Monday, February 27, 2017 at 2:33:08 PM UTC+2, Marcus > > Weseloh > > > > wrote: > > > > > > > >> Hi, > > > >> > > > >> 2017-02-27 13:11 GMT+01:00 oliver <oli...@schinagl.nl>: > > > >> > > > >>> One is to remove C185 (10 microF) and the problem went > > away. > > > >>> Looking at other designs, cubieboard 1 for example, uses > > the same > > > >>> layout, but only 4.7 microF. So it seems that charging of > > all the > > > >>> capacitance (input C106) the board itself, the output > > (C185) may > > > >>> be too much for the AXP209. > > > >> > > > >> Great, that confirms my suspicion that the capacitance is > > the main > > > >> problem on the A20-SOM. The reference design for the A20 > > from > > > >> Allwinner also suggests 4.7uF on LDO3, Olimex probably > > used 10uF > > > >> there to keep the BOM smaller? > > > >> > > > >> At least on the A20-SOM-EVB we have another problem though > > (as > > > >> explained in an earlier mail): When then SOM is attached > > to the EVB, > > > >> the LDO3_2.8V rail on the SOM is powered from the EVB via > > +5V and a > > > >> DC converter. Even with the LDO3 voltage set to it's > > minimum, > > > >> turning on LDO3 shuts down the AXP immediately. Probably > > because the > > > >> AXP sees an external voltage applied to it's input, it > > might even > > > >> see reverse current flowing into it's ouput. I'd say that > > this is a > > > >> design flaw on the EVB. So at least on the A20-SOM-EVB > > combination, > > > >> LDO3 should never be be allowed to be switched on. > > > >> > > > >> Cheers, > > > >> > > > >> Marcus > > > -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
