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tensaisakuragi06
Associate III
May 14, 2026
Solved

STM32U083CC Design Considerations USB

  • May 14, 2026
  • 5 replies
  • 174 views

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?VDD USB.jpg

Best answer by 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

5 replies

Andrew Neil
Andrew Neil
Super User
May 14, 2026

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


A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
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    tensaisakuragi06Author
    Associate III
    May 14, 2026

    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.

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    tensaisakuragi06Author
    Associate III
    May 14, 2026

    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.

    G
    GyessineAnswer
    Technical Moderator
    May 14, 2026

    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

    To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
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      tensaisakuragi06Author
      Associate III
      May 15, 2026

      It make sense now. I need to operate MCU at Low Power Mode. So, it will probably need externall supply if i use USB. Tahnk you for helps.

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