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Measuring Current on NUCLEO-N657X0-Q

Dresult
Associate III

Hi everyone,
I'm trying to measure the current consumption of the MCU/NPU on a NUCLEO-N657X0-Q board. According to the reference manual (https://www.st.com/resource/en/user_manual/um3417-stm32n6-nucleo144-board-mb1940-stmicroelectronics.pdf - see par. 7.4.4), I tried both removing resistor R13 and measuring the current with a multimeter across pins 9-10 on CN12, and removing R40 and measuring across pins 3-4. In the first case, I couldn't measure anything at all, so I assumed the board was in SPMS mode and tried the second option instead. However, when measuring the current across pins 3-4, I got a reading in the order of 40 microamps, which seems implausible. Notably, I'm trying to measuring while AI validation is ongoing in CubeMX.

I'm wondering whether I might have made a mistake with the board, or if the issue lies with the measuring instrument.

 

Thanks!

1 ACCEPTED SOLUTION

Accepted Solutions
David SIORPAES
ST Employee

Hello,

After removing R40, current flows through R41 shunt resistor (50 mOhms). So, with the multimeter you should measure voltage drop on CN12 3-4 pins (not current) and then compute the resulting current: I=Vshunt/50m

 

Hope this helps,

David

 

View solution in original post

2 REPLIES 2
David SIORPAES
ST Employee

Hello,

After removing R40, current flows through R41 shunt resistor (50 mOhms). So, with the multimeter you should measure voltage drop on CN12 3-4 pins (not current) and then compute the resulting current: I=Vshunt/50m

 

Hope this helps,

David

 

Thank you very much, I did not know that. I had read the manual (section 7.4.4, second bullet) word by word and was convinced that from those pins I could measure a current.