Vbat minimum on STM32N6

[bashReflex]

I am designing the power system for an application using the STM32N645. In the datasheet for the STM32N6x5 minimum Vbat is defined as "TBD". In the STM32N6570-DK schematic the Vbat rail is set to 3.3V. If it can operate at 1.8V it would simplify the power architecture.

Does anyone have any experience with running it at 1.8V? Or is there a timeline for when this specification will be released?

Thanks!

-Bash

[KDJEM.1]

Hello @bashReflex and welcome to the Community;

 

I will check the minimum VBAT value on STM32N6 internally. I will get back to you as soon as possible.

Internal ticket number: 215811 (This is an internal tracking number and is not accessible or usable by customers).

 

Thank you.

Kaouthar

[tylerl]

In later revisions of the datasheet the minimum Vbat has been changed to 3.0V.  Can you shed some light on why 3.0V was chosen?  It looks like everything that Vbat powers should theoretically work below 3V(in particular VSW is good down to 2V).  The reason I’m asking is that if we follow the 3.0V to 3.6V window strictly there is not a good primary cell chemistry that matches that.  Lithium manganese dioxide is too low of a voltage for most of the discharge curve.  Lithium thionyl chloride would work well but a fresh cell will be a little above 3.6V.

Is lithium thionyl chloride the intended chemistry?  Chances are it would probably just work since it would be below the absolute max rating.  Does ST have an intended backup supply architecture for Vbat other than applying a cell voltage directly to Vbat?