Is it normal that after cutting SB8 our chip is still working when connected to USB port? (in case of battery we need to connect pin 1 and 2 from P1). I spend long time looking at schematic of this board and still don't understand why USB is different than battery or external power source.
Thanks in advance for your help
It could be sourced by the P8 header (SWD interface) which is connected to the SEGGER chip.
A possibility can also be the UART lines from the SEGGER.
Try cutting/removing jumper on these lines and see if that helps the situation.
Thank you Hakon for your response. I could try cutting this jumpers, but not sure if it is a great solution. After that I won't be able to use some of the board functionalities. If I am right it is not Ok that board is powered through different pins then VDD?
You do not need to cut the wires on the SWD interface, you can just remove the jumpers on P8, or if you have a newer HW revision of the board, set the switch in the "OFF" position.
If that does not work, there are solder-bridges marked "CTS/RTS/TxD/RxD" between the SEGGER and the nRF that can be cut and later on re-soldered if you're using UART communication.
I have a newer HW revision. I will try to cut those bridges today because setting switch in the OFF position didn't solve the problem. I will let you know whether it helps me.
After cutting SB9-12 bridges (not only SB8) board works as it should - without a jumper on P1 header uC won't be powered. I am not sure if it is desired behaviour, but without this board will be powered from USB even though SB8 is cutted.
Thank you Hakon for your help.