DocID027916 Rev 2
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UM1902
Hardware layout and configuration
78
The following power sequence procedure must be respected:
•
Connect jumper JP13 for PSU or D5V side
•
Check that JP15 is removed
•
Connect the external power source to PSU or D5V (daughterboard mounted)
•
Check red LED LD10 is turned ON
•
Connect the PC to USB connector CN21
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 300 mA 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. 300 mA will be requested at enumeration (since JP15 must be OFF), so there is risk
that request is rejected and enumeration does not succeed if the PC cannot provide
such current. Consequently the board is not powered (the led LD10 remains OFF).
Note:
In case the board is powered by an USB charger, there is no USB enumeration, so the led
LD10 remains set to OFF permanently and the board is not powered. Only in this specific
case the jumper JP15 needs to be set to ON, to allow the board to be powered anyway but
in any cases the current will be limited to 600 mA by U17 (ST890).
The power supply is configured by setting the related jumpers JP2, JP9 and JP13 as
described in
Table 1. Power related jumpers
Jumper
Description
JP2
JP2 is used to measure STM32 current consumption manually by multimeter.
Default setting: Fitted
JP9
V
bat
is connected to +3.3 V when JP9 is set as shown to the right
(Default setting):
V
bat
is connected to battery when JP9 is set as shown to the right:
JP13
JP13 is used to select one of the six possible power supply resources.
For power supply jack (CN17) to the STM32746G-EVAL only, JP13 is set as shown
to the right (Default setting):
+6
)6
)6
'9
368
67ON
069