DocID028599 Rev 7 23/82
UM1974 Hardware layout and configuration
81
Using V
IN
or E5V as an external power supply
When powered by V
IN
or E5V, it is still possible to use the ST-LINK for programming or
debugging only, but it is mandatory to power the board first using V
IN
or E5V, then to
connect the USB cable to the PC. In this way the enumeration succeeds, thanks to the
external power source.
The following power-sequence procedure must be respected:
1. Connect jumper JP3 between pin 1 and pin 2 for E5V or between pin 5 and pin 6 for
V
IN
2. Check that JP1 is removed
3. Connect the external power source to V
IN
or E5V
4. Power on the external power supply 7 V< V
IN
< 12 V to V
IN
, or 5 V for E5V
5. Check that the green LED LD6 is turned ON
6. Connect the PC to the USB connector CN1
If this order is not respected, the board may be powered by USB (U5V) first, then by V
IN
or
E5V as the following risks may be encountered:
1. If more than 300mA current is needed by the board, the PC may be damaged or the
current supplied can be limited by the PC. As a consequence the board is not powered
correctly.
2. 300mA is requested at enumeration (since JP1 must be OFF) so there is risk that the
request is rejected and the enumeration does not succeed if the PC cannot provide
such current. Consequently the board is not power supplied (LED LD6 remains OFF).
Table 8. Power related jumper
Jumper Description
JP3
U5V (ST-LINK V
BUS
) is used as power source when JP3 is set as shown to the right
(Default setting)
E5V is used as power source when JP3 is set as shown to the right:
V
IN
is used as power source when JP3 is set as shown to the right:
(9
89
9,19
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