S32K344 V15 from external SBC power sequence requirement

[KarelAd]

Hello,

There is an option "V15_extended defined for 1.4 - 5.5 V" in datasheet so the V15 pin can be powered also by higher voltages instead of BJT transistor regulator or 1.5V external source. So I could use 1.8V rail already available in my design to supply V15 pin while considering thermal aspects, Am I right? My goal is to save some power burned in the BJT regulator.

Are there any power-up, power-down sequence requirement for VDD_HV and V15 when V15 powered by external PSU or all MCU PSUs can operate independently?

Is there any drawback of this solution I should be aware of? I'm using 257MBGA.

How HVD_V15 set for 2.5V works if the V15_extended is defined up to 5 V? Will it trip in this case?

Regards,

Karel

[davidtosenovjan]

I have just obtained an answer from application team. I am sharing how it is:

“From a voltage robustness perspective, just for the K31X/K32X and K34X parts allow up to 5.5V on V15. 

However, for an application using more than 1.5V, the max die temperature Tj must be analyzed as MANDATORY. The max die temperature must not reach values beyond +150oC.

It is a matter of effective thermal resistance, run current of the application and input voltage where it ends up.

In my opinion, the V15_extended range is not recommendable for medium-High temperature applications. 

I'm working to add these considerations and limitations in the new version of the DS”

[davidtosenovjan]

I have forwarded your question to application team, until now I don't have an answer.