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 ...