I'm currently developing an IoT LoRa node using a Nucleo L432KC. I want the node to be alive more than a year, so I want to test its energy consumption very carefully.
I intended to cut off any unnecessary devices on the Nucleo board, starting with:
- R22 to cut-off LD2 LED (power supply)
- D2 to cut-off +3V3_ST_LINK, so the ST-LINK is not supposed to be powered
I power supply the board through Vin (9V).
I did some tests and the whole board is consuming 19 mA when running (idle) and 6 mA in stand-by mode. I don’t understand where those 6 mA are coming from. The STM32L432KC is consuming few uA so it’s not up to the microcontroller (tested with an amperemeter on JP1).
However, the 3V3_ST_LINK voltage which is supposed to be 0V is at 0.85V when the L432 is in sleep mode and 2.65V when it’s running. I don’t know what the origin of this voltage is and I don’t know either where the 6 mA are coming from.
Any idea? :)
Thank you! You can be my hero of the day, maybe of the week!
NB: sch of the board page 29-31 of this doc => http://www.st.com/content/ccc/resource/technical/document/user_manual/e3/0e/88/05/e8/74/43/a0/DM00231744.pdf/files/DM00231744.pdf/jcr:content/translations/en.DM00231744.pdf