Is it okay to have VBAT=3.67 V & VDD=3.3V for STM32L4R?

[krn]

I am using STM32L4R, the VBAT pin is powered by 3.6V +/- 2% & VDD is powered by 3.3V +/- 2%.

I think it is okay to have VBATT as 3.67V_max since it is still less than Absolute Max limit of 4V.

I think it is okay to have VBAT pin & VDD pin at different voltage level since at a time either one of these is selected to power RTC. Also, the voltage rating mentioned in electrical specification is in absolute terms (not relative to VDD).

Please confirm if my understanding is correct.

[SofLit]

Hello,

Yes you can use VBAT and VDD at different voltages.

Bear in mind that the maximum allowed voltage of VBAT is 3.6V as stated in the DS:

Exposure to maximum rating conditions for extended periods may affect device reliability:

So we cannot guarantee the behavior of the product above the maximum values provided in the DS after a long time period of function.

[krn]

Hello, 

Thank you for the reply.

The Absolute Max rating for VBAT pin is 4V.

I think it is okay to have VBATT as 3.67V_max since it is still less than Absolute Max limit of 4V.

Please can you confirm this understanding is correct.

Regards

Karan

[SofLit · Accepted solution]

Hello,

I can explain it as following:

There are three ranges:

•  V  =< Vmax: you can guarantee that your product will work without any issue during his product lifetime and its characteristics are not changed during this period.
• Vmax < V < V absolute ratings : The product is not damaged but there is a risk of its performance/characteristics decrease/degradation during his lifetime.
• V > V absolute ratings: you risk to damage your product permanently.

Hope it does answer your question.