External Power Supply Output - ST STM32 User Manual

UM1974
Using V
When powered by V
debugging only, but it is mandatory to power the board first using V
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
4. Power on the external power supply 7 V< V
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
E5V as the following risks may be encountered:
1. If more than 300 mA 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. 300 mA 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).
External power supply input: + 3.3 V
When the 3.3 V is provided by a shield board, it is interesting to use the +3.3 V (CN8 pin 7 or
CN11 pin 16) directly as power input. In this case the programming and debugging features
are not available, since the ST-LINK is not powered.
When the board is powered with +3.3 V, two different configurations are possible:
•
ST-LINK is removed (PCB cut)
•
SB3 (3.3 V regulator) and SB111 (NRST) are OFF.
6.4.3

External power supply output

When powered by USB, V
output power supply for an ST Zio shield or an extension board. In this case, the maximum
current of the power source specified in
The +3.3 V (CN8 pin 7 or CN11 pin 16) can be used also as power supply output. The
current is limited by the maximum current capability of the regulator U6 (500 mA max).
or E5V as an external power supply
IN
or E5V, it is still possible to use the ST-LINK for programming or
IN
or E5V, the +5 V (CN8 pin 9 or CN11 pin 18) can be used as
IN
or E5V
IN
< 12 V to V
IN
Table 7: External power sources
UM1974 Rev 9
Hardware layout and configuration
or E5V, then to
IN
, or 5 V for E5V
IN
must be respected.
or
IN
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