STM32U083CC Design Considerations USB

[tensaisakuragi06]

I am planning to use STM32U083CC series MCU in my project and after inspecting datasheet there is a line "Vddusb should be preferably connected to Vdd when the USB is not used)". I know that Vddusb is independent from Vdd but is it omitted that i can not use Vdd for Vddusb? I mean should i need extra AMS1117 3.3 for instance to feed Vddusb?

[Andrew Neil]

Have you seen Application note AN5938, Getting started with STM32U0 MCUs hardware development ?

[tensaisakuragi06]

I only see datasheet and RM053 technical reference. I did not start to inspect technical reference but i fully inspect datasheet. I look at that document now(AN5938). In related documents after dahasheet tecnhnical reference end errate sheet mentioned ned that application note. I keep in my mind if there is an applicaiton note.

[tensaisakuragi06]

It seems i need to supply it without using Vdd not to reduce current supply capacity of MCU. Its a little hard for me. I need to supply MCU, and i need Vref voltage for ADC and Vddusb. Three independent supply source i need.

[Gyessine]

Hello @tensaisakuragi06 
If your main VDD supply is within the USB operating range (typically 3.3 V), it is acceptable and common to connect VDDUSB directly to VDD.If your application requires the MCU to operate at a voltage lower than the USB transceiver’s minimum (for example, below 3.0 V), you must provide a separate 3.3 V supply to VDDUSB
You can refer to AN4879 power section
BR
Gyessine