confusion about power ic axp209

[Peter G.]

I am a little confused about how the A20 board power works in general.I understand from schematics that
AXP209's DCDC2 pin is used for VDD-CPU  and DCDC3 for VDD-SYS.
DCDC3 can be set to 1.2 volt if pin DC3SET is kept floating, I understand so far.But there is no way to set default voltage of DCDC2, it can only be programmed.What I dont understand is the cyclic dependency that DCDC2 is used for providing VDD-CPU, but it needs to be programmed first.How is it supposed to be programmed when CPU is not started yet.Please someone help me understand this.

[Pawel_W]

I had to replace AXP209 chip because I fried it by connecting the lithium battery with reverse polarity. Fortunately the rest of the A20 device is protected by diode, but not this chip.
With new stock chip Android refused to start without connected battery (Debian started correctly).
So the Olimex's AXP209 must have been programmed (non-volatilely) to allow Android to start without battery. It's quite complex chip, that even allows to store some boot crypto key inside!