Figure 5. Structure Of Power Source - ST STM32091C-EVAL User Manual

Hardware Layout and configuration
If this order is not respected, the board may be powered by VBUS first then E5V or D5V,
and the following risks may be encountered:
1. If more than 300mA current is needed by the board, the PC may be damaged or
current can be limited by PC. As a consequence the board is not powered correctly.
2. 300mA will be requested at enumeration (since JP18 must be OFF), so there is risk
that request is rejected and enumeration does not succeed if PC can't provide such
current. Consequently the board is not powered (LED LD5 remains OFF).
Note: In case the board is powered by an USB charger, there is no USB enumeration, so the led
LD5 remains set to OFF permanently and the board is not powered. Only in this specific
case the jumper JP18 needs to be set to ON, to allow the board to be powered anyway.
Figure 5
board.
The power source is selected by setting the related jumpers JP15, JP7 and JP10 as
described in
12/58
will help you to understand the structure of the power source on the evaluation

Figure 5. Structure of power source

Table 1.
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