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Current measurement on the PCA 10040 v1.1.0 (NRF52)

Felipe Ribas

Hi,

I was reading the procedure to prepare the NRF52 DK board for current measuring and some questions came into my mind. I understand we have to open the P22 so we interrupt the circuit to measure the flowing current. But then it says to bypass the safety diodes (either for battery supply or ext. supply). Questions:

-why bypass the safety diodes? It says " This bypasses a USB supply protection diode and ensures all ICs on the development kit have equal supply voltage to avoid leakage from the nRF52 GPIO". But say I'm using ext. power supply. So, according to the hardware schematics of the board, everything is connected after the diode and there's nothing connected between the diode and the power supply itself. In this case, how would something have different voltage levels?

-I'm using the same approach in my project which is the safety diodes to allow the user plugging/unplugging ext. power supply and automatically switching to battery if needed. Is this a bad solution for a final project?

I thought this diodes were supposed to have a very low dropout voltage so I should just forget that they are there and use/measure everything as if they don't exist...

Thanks in advance!

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    Hi, it is correct that both VDD and VDD_nRF is after the diode, so there shouldn't be anything that has different voltage levels. I guess the only purpose of bypassing the diode is to get rid of the voltage drop. It is not very big, but if you want to know the exact voltage you are measuring on it could be an idea to bypass it. Or you could just measure the voltage after the diode and adjust the input voltage accordingly.

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