6.4.2
External Power supply inputs
The STM8 Nucleo-32 board and its shield boards can be powered in three different ways from an external power
supply, depending on the voltage used. The three power sources are summarized in
Table 5.
External power sources
Input
power
name
Connector pins
Voltage range
Max.
current
Limitation
VIN
CN4 pin 1
7 to 12 V
800 mA
From 7 to 12 V only and input current capability is linked to input
voltage:
•
800 mA input current when VIN = 7 V
•
450 mA input current when 7 V < VIN < 9 V
•
300 mA input current when 9 V < VIN < 10 V
•
Less than 300 mA input current when 10 V < VIN
5V
CN4 pin 4
4.75 to 5.25 V
500 mA ST-LINK not powered
3V3
CN4 pin 14
3.0 to 3.6 V
-
ST-LINK not powered and SB13 must be OFF.
VIN or 5V power supply
When powered from VIN or 5V, it is still possible to use ST-LINK for communication for programming or
debugging only, but it is mandatory to power the board first, using VIN or 5V, then to connect the USB cable to the
PC. In this way, the enumeration always succeeds, thanks to the external power source.
The following power sequence procedure must be respected:
1.
Check that SB1 is OFF
2.
Connect the external power source to VIN or 5V
3.
Power on the external power supply 7 V < VIN < 12 V to VIN, or 5V
4.
Check red LED LD2 is turned ON
5.
Connect the PC to USB connector CN1
If this order is not respected, the board may be powered by V
BUS
first, then by VIN or 5V, 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 supplied is limited
by the PC. As a consequence, the board is not powered correctly.
2.
300 mA is requested at enumeration (since SB1 must be off) so there is the 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 LD2 remains OFF).
3V3 power supply
When the board is powered by 3V3 (CN4 pin 14), the solder bridge SB13 must be OFF.
Using the 3V3 (CN4 pin 14) directly as power input can be interesting, for instance, in case the 3.3 V is provided
by a shield board. In this case, the ST-LINK is not powered, thus programming and debugging features are not
available.
In addition, to ensure powering the MCU, JP1 must be set to position [1-2].
6.4.3
External Power supply output
When powered by USB or VIN, the 5V (CN4 pin 4) can be used as an output power supply for an ARDUINO
®
Nano shield. In this case, the maximum current of the power source specified in
Table 5. External power sources
must be respected.
The 3.3V (CN4 pin 14) can be used also as a power supply output. The current is limited by the maximum current
capability of the regulator U7 (500 mA max).
UM2391
Power supply and power selection
UM2391
-
Rev 1
page 13/25
