U2 started smoking

[MichMich]

Hi There!

Yesterday I was cleaning out my drawer and found a Badgy REV1 that I hadn't tried for a while. I hooked it up 2 a micro usb connector to see if it would power up (without a battery). The display did a nice redraw, but then I noticed some magic smoke, so I quickly disconnected the USB wire.

It looks like U2 is the one that was fried. But I don't really understand what the reason is for this. Especially without battery.

Any idea what the reason can be?

Thanks!