Figure 8. 5 V Power Structure - STMicroelectronics STM32G081B-EVAL User Manual

Hardware layout and configuration
The STM32G081B-EVAL Evaluation board can be powered from the ST-LINK/V2-1 USB
connector CN6 with a PC, but only the ST-LINK/V2-1 circuit has the power before USB
enumeration, because the host PC only provides 100 mA to the boards at that time. During
the USB enumeration, the STM32G081B-EVAL board requires 300 mA power from the host
PC. If the host is able to provide the required power, the enumeration succeeds, the power
transistor U5 is switched ON, the red LED LD7 is turned ON, and thus the STM32G081B-
EVAL board is powered and can consume maximum 300 mA current. If the host PC is not
able to provide the requested current, the enumeration fails. Therefore the STM32 part
including the extension board is not powered. As a consequence the red LED LD7 remains
turned OFF. In this case it is mandatory to use an external power supply to supply extra
power.
E5V (from PSU) or D5V can be used as external power supply in case current consumption
of the STM32G081B-EVAL board exceeds the allowed current on USB. In this condition it is
still possible to use USB for communication, for programming or debugging only, but it is
mandatory to power the board first using E5V or D5V, and then connecting the USB cable to
the PC. Proceeding this way ensures that the enumeration succeeds thanks to the external
power source.
The following power sequence procedure must be respected:
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Figure 8. 5 V power structure

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UM2403