After firmware flash, first time STOP 3 mode power consumption is higher (if board is not power cycled)

[devfwtest]

Hello,

We are using STMU575 MCU and it's power saving mode STOP3.
For verification purpose we are using NUCLEO-U575ZI-Q eval board, ST cube example PWR_LPMODE_RTC (STM32CubeU5-1.7.0). ST cube IDE version is: 1.18.0.
I modified existing code little bit (as per suggestion by ST team in other thread 735939)to make it work for STOP 3 mode.

For current measurement, connected current meter between JP5. 

When I am running this code, I am observing following thing:

After firmware flash, when first time code is executed (with NRST reset and without USB power removal) and enters in to STOP 3 mode, current consumption shows 0.19 mA.
When I remove board's USB cable and insert it again to power cycle it to execute the code and enter in to STOP 3 mode, it shows current consumption very low compare to first time (~0 mA with 3¾ digit multimeter).
Trying to know why current consumption is higher first time after firmware flash (without power cycle) in comparison with current consumption after board power cycle.

Please assist.

[Andrew Neil]

Yes, a power cycle is needed:

https://community.st.com/t5/stm32-mcus-wireless/how-to-reduce-the-power-consumption-of-stm32wb55-stop2-mode/m-p/785696/highlight/true#M23997

[devfwtest]

Thank you for quick response.

Is there any other option to reduce current consumption without doing power cycle? As our end product device is super cap (back up) powered, power cycle is not feasible until cap is fully discharged.

[Andrew Neil]

Are you flashing via CubeIDE or CubeProgrammer ?

[devfwtest]

Flashing with Cube programmer.