Skip to main content
L
LimoGr
Visitor II
March 13, 2023
Solved

Power Supply for STM32F4 Board via USB Vbus

  • March 13, 2023
  • 1 reply
  • 3675 views

Hi! I am working currently on a stm32 F407, I am implementing USB Communication Device Class with the microcontroller being a device. The microcontroller is powered via the STLink but I wanted to change that and supply it through the usb I am using for virtual communication. On the data brief, it says that the board has a Flexible power-supply options: ST-LINK, USB VBUS, or external sources. I assume that I have to use the USB Vbus.

The reference manual says that :

On-chip 5 V VBUS generation is not supported. For this reason, a charge pump or, if 5 V are available on the application board, a basic power switch must be added externally to drive the 5 V VBUS line. The external charge pump can be driven by any GPIO output. This is required for the OTG A-host, A-device and host-only configurations. The VBUS input ensures that valid VBUS levels are supplied by the charge pump during USB operations while the charge pump overcurrent output can be input to any GPIO pin configured to generate port interrupts. The overcurrent ISR must promptly disable the VBUS generation.

My question is does that mean that I have to add a circuit to my board in order to connect the Vbus with a GPIO and that's how I am going to supply it through the USB or I did not understand well?

Thank you

    This topic has been closed for replies.
    Best answer by KDJEM.1

    Hello @LimoGr​ ,

    In the datasheet and precisely in Absolute Maximum Rating (AMR) table is stating that a +5V tolerant pin voltage can be maximally VDD+4V. So the situation where the MCU is not powered and 5V VBUS is connected to PA9 must be avoided because it is violating AMR.

    Two solutions can be proposed:

    •  Solution with a dedicated VBUS pin (PA9 or PB13): The usage of a voltage divider is recommended.
    •  Solution without usage of a dedicated VBUS pin: Any 5V tolerant pin with external interrupt functionality can be used with an external resistor divider, to fulfill AMR conditions.

    For more explanation, I recommend you this FAQ: Management of VBUS sensing for USB device design.

    When your question is answered, please close this topic by choosing Select as Best. This will help other users find that answer faster.

      

    Kaouthar

    1 reply

    K
    KDJEM.1Answer
    Technical Moderator
    April 4, 2023

    Hello @LimoGr​ ,

    In the datasheet and precisely in Absolute Maximum Rating (AMR) table is stating that a +5V tolerant pin voltage can be maximally VDD+4V. So the situation where the MCU is not powered and 5V VBUS is connected to PA9 must be avoided because it is violating AMR.

    Two solutions can be proposed:

    •  Solution with a dedicated VBUS pin (PA9 or PB13): The usage of a voltage divider is recommended.
    •  Solution without usage of a dedicated VBUS pin: Any 5V tolerant pin with external interrupt functionality can be used with an external resistor divider, to fulfill AMR conditions.

    For more explanation, I recommend you this FAQ: Management of VBUS sensing for USB device design.

    When your question is answered, please close this topic by choosing Select as Best. This will help other users find that answer faster.

      

    Kaouthar

    Terms & ConditionsAccessibility statement