USB-C on STM32H753

MFawzy · ‎2025-10-14

Hi,

I’m implementing a self-powered USB 2.0 Full-speed device with an STM32H753XI and a USB-C connector.
Could you please confirm that the attached schematic:

Uses STM-recommended resistor values for the VBUS-sense divider on PA9 to prevent MCU damage if the USB is connected while the MCU isn't powered (MCU is self-powered)
Omitting the 22 Ω series resistors on USB_P/USB_N is acceptable for device-only operation.
Provides complete ESD/over-voltage protection for the MCU.
Contains all capacitors / resistors required for reliable enumeration and long-term robustness.

Thanks in advance for your feedback.

Best regards,

FBL · ‎2025-10-17

Hi @MFawzy

Your current resistor divider (33 kΩ and 82 kΩ) scales 5 V VBUS down to approximately 1.435 V on PA9, which is within safe input voltage limits. However, checking the STM32H753XI, PA9 is already 5V tolerant. So in this case, no need to add resistor divider;

However, the key risk in self-powered systems is the possibility of back-powering the MCU through the input protection diodes on PA9 when the MCU VDD is unpowered.

You can refer to MB1364 to check PA9 configuration.

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