STM32U5: Is the consumption below brownout level 0 defined and how do I keep it low?

[OliM]

We are planning a circuit were one PCB needs to be charged from another one. The first will have some capacitors whereas the second has a battery. This means the charging should be as power conscious as possible.

We tried to find out what the consumption of the U5 on the charged PCB would be until it can leave brownout. We didn't find anything in the datasheet so we did some measurements with the U575 Nucleo (at the IDD jumper): Below 1.7V it went up to ~90µA (was in Stop before, so a nearly ten fold increase), at 1.4V it increased to up to 180µA and only below 1V it continues to fall linear from 100µA down.

Is this expected behavior or is this something down to the Nucleos circuitry? And can I find a document somewhere specifying that behavior (can it be worse?)?

[Sarra.S]

Hello @Oliver Müller​,

Could you please specify your configuration? which peripheral are disabled, enabled?

your measurements are in stop mode? are we talking about Stop2 mode (8.9µA in 1.8V)?

Please provide more details so I can reproduce the measurement on my side

Thank you!

Sarra

[OliM]

The base measurement was Stop2 mode at ~9µA at 1.8V with full SRAM retention and only LPTIM running. So as expected from the datasheet.

My question mainly relates to the brownout state (entered from Stop2), which is not further defined in the datasheets I found.