STM32 NUCLEO-F767ZI 3.3V power source from X-NUCLEO-LPM01A
Hi,
I am trying to power up my F767ZI board from the 3.3V power given by X-NUCLEO-LPM01A. Strangely, when I measure the voltage from X-NUCLEO-LPM01A with a multimeter (on the 3.3V input pins on the F767ZI board), I see the output voltage is only 1.6V to 1.7V (or about1.2V if I pull a wire from 3.3V input to SWD's RST signal to prevent STLINK from resetting my board[*]), despite that I had set it to 3.3V. The board does not start up as well.
More observations:
1) This only happens when I use X-NUCLEO-LPM01A as power source. When I used another DC power source, I could measure 3.3V on the board's 3.3V input pins just as I set it. The program on board also run normally.
2) This only happens when I set X-NUCLEO-LPM01A's output voltage to 3V or 3.3V. When I tried setting it to 2.4V, I measured 2.4V on the board's input pins, and the program on board could run.
3) This only happens when I use F767ZI. I have tried G0B1RE, L4R5ZI and U575ZI and all of those could work normally.
Additional information:
I have removed SB3 from the board to prevent the 3.3V input from going into the on-board 3.3V voltage regulator. This however had happened even before I remove it, so I don't think the regulator plays a part.
I have not found an answer from the board's manual, and I appreciate it very much for any help.
[1] I do this because boards like F767ZI does not have a jumper to disconnect STLINK's reset signal, and thus I found the board is always in reset if STLINK is not powered. For this board, I have not removed SB111 to disconnect STLINK reset, so I would just connect 3.3V to the NRST pin of SWD to prevent getting the RST signal from STLINK.