Hello together,
I have created a nRF52840 board that fit the dimensions of my project I am working on. I've gotten it made by jlc.
However as soon as I plugged in USB, after testing for hard shorts via multimeter, the MCU started heating up heavily immediately. As I knew that I probably fried it, I plugged it in a second time for a few seconds to quickly measure the 3V3 rail via the testpad and it measured 5.6 ish volts.
I now tried it with a bench PSU, connecting it directly to the 3V3 Testpad and the GND Testpad, setting it to 3.3V and 50mA, nothing happened. I slowly upped it, till at 0.3A it still showed C.C and the MCU heated up again.
Despite all of this I neither can find any issue in the schematic nor any obvious mistake in the layout. I would highly appreciate having another pair of eyes looking over it, thank you!