Current drift in STM32U5

[OptimusPyne]

Hello,

We are using an STM32U585RIT6 and doing some power measurement. What we are seeing is that the current drops to within the expected range when we put the MCU to sleep, but the current changes over time.

Basically:

• Go into stop mode 2
• Current measures around 22µA at first (entire board)
• The current then slowly moves down to around 17/18µA over the course of a couple minutes.
• The current will then jump up to ~28µA and then begin drifting down again.

Doing the same test with stop mode 3 results in the same behavior, but all number are lower, including the jump. With stop mode 2 it jumps about 10µA, with stop mode three it only jumps about 4µA. The fact that the size of the jump (and that we've pulled nearly everything else off the board) indicates that the irregular current is related to the MCU.

We've set every unused pin to be an input with a pulldown.

Is this current drift normal with this MCU in sleep mode?

Thank you

[STOne-32]

Dear @OptimusPyne ,

So if we summarize the behavior - You see about 5 to 6uA drifting minus/plus 22uA total board consumption.

is it possible to try to trace it to see the shape of the variation other time ? 
Do you know if using LDO or SMPS and what is the VDD range ? If possible which is the closed configuration versus our datasheet here : https://www.st.com/resource/en/datasheet/stm32u585ai.pdf#page166 starting from Page 184 ?

to see also external Pins on boards if not active devices / memories on board ?

Hope it helps .

STOne-32

[Uwe Bonnes]

Did you check that all floating pins are in analog mode? A floating pin can also cause current shift.

[Christian N]

This post has been escalated to the ST Online Support Team for additional assistance. We'll contact you directly.

[OptimusPyne]

All floating pins were set as inputs with pulldowns.