What is the Stm32L4 VDD12

[A.Caliskan]

"Hello, while examining the STM32L412C8 microcontroller, I came across the term VDD12. What is VDD12, and can I use the peripherals without making the VDD12 connection? In other words, is it mandatory to make the VDD12 connection?"

[Artur IWANICKI]

Hello,

This pin is available only within packages with an external SMPS supply option (having P or PTR suffix in the marking, i.e. STM32L412RBT6P) and it is connected directly to Vcore power line (Core, Memories and Digital peripherals supply).

Vdd12 power supply line can be used to bypass the internal LDO regulator when using an external SMPS.
In such a case you need to apply there voltage in range 1 .. 1.32V.
It doesn't require any external decoupling capacitor and it does not support any external load.

In case you would like to use an internal LDO, please keep this line unconnected.

More information on that you can find within dedicated application note, AN4978 "Design recommendations for STM32L4xxxx with external SMPS, for ultra-low-power applications with high performance"