5) External power supply input from external 5 V
When a shield board provides the 5 V, it is interesting to use the 5V (CN3 pin 4) directly as power input (refer to
Table 7). In this case, the programming and debugging features are not available, since the ST-LINK is not
powered.
Table 7. External power sources: 5V
Input power name Connector pins Voltage range Maximum current
5V CN3 pin 4 4.75 V to 5.25 V 500 mA
6.4.1 Debugging while using VIN or EXT as an external power supply
When powered by VIN or 5V, it is still possible to use the ST-LINK for programming or debugging only, but it is
mandatory to power the board first using VIN or EXT (either 3V3 or 5V), then to connect the USB cable to the PC.
By acting this way, the enumeration succeeds, thanks to the external power source.
The user must respect the following power-sequence procedure:
1. Connect the external power source to VIN or 5V
2. Power on the external power supply 7 V< VIN < 12 V for VIN, or 5 V for 5V
3. Check that the green LED LD4 (5V_PWR) is turned ON
4. Connect the PC to the USB connector CN1
If this order is not respected, the board may be powered by USB first, then by VIN or 5V as the following risks
may occur:
1. If the board needs more than 300 mA current, the PC may be damaged or can limit the current supplied.
Consequently, the board is not powered correctly.
2. Enumeration requests 300 mA, 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 LD3
remains OFF).
3V3 power supply
Using the 3V3 (CN3 pin 14) directly as power input, can be interesting, for instance, in case a shield provides the
3.3 V. In this case the STLINK-V3E is not powered, thus programming and debugging features are not available.
5V power supply
Using the 5V (CN3 pin 4) directly as power input, can be interesting, for instance, in case a shield provides the
5 V. In this case the STLINK-V3E is not powered, thus programming and debugging features are not available.
External power supply output
When powered by USB or VIN, the 5V (CN3 pin 4) can be used as output power supply for an ARDUINO
®
Nano
shield. In this case, the user must respect the maximum current of the power source specified in “External power
sources” table.
The 3V3 (CN3 pin 14) can be used also as power supply output. The maximum current capability of the
LD39050PU33R regulator U9 (500 mA max) limits the available current.
6.5
Clock sources
There are four ways to configure the high-speed clock to use.
UM2397
Clock sources
UM2397 - Rev 2
page 14/30
To Next Page
Loading...
Need help?
General
