ST Nucleo-64 STM32U3 User Manual page 24

7.4.2 Programing/debugging when the power supply is not from STLINK-V3EC (STLK)
In case the current consumption of the Nucleo-64 and the expansion boards exceeds the allowed current on the
ST-LINK USB connector, the external power VIN, E5V, or USB-USER can be used. In such a case, it is still
possible to use the embedded ST-LINK for VCP, programming, and debugging.
In this case, the following power sequence procedure must be respected:
1. Set the JP3 jumper according to the 5V selected external power source.
2. Connect the external power source according to JP3.
3. Switch on the external power supply.
4. Check that the 5 V green LED (LD3) is turned ON.
5. Connect the PC to the USB connector (CN1) for programming/debugging.
If this sequence is not respected, V
might be encountered:
• If the board needs more than 500 mA, the PC might be damaged or limit the current. Therefore, the board
is not powered correctly.
• 500 mA is requested at enumeration. Thus, there is a risk that the request is rejected. Enumeration does
not succeed if the PC cannot provide such a current.
Consequently, the board is not powered, and the 5 V green LED (LD3) remains OFF.
7.4.3 Power supply output
• 5V: Whatever the power source (STLK, VIN_5V, E5V, CHGR, or USB-USER), the 5V generated is present
on CN6 pin 5 or CN7 pin 18, and can be used as an output power supply for an ARDUINO
extension board. In this case, the maximum current of the power source specified in
respected.
• 3V3: The internal 3V3, on CN6 pin 4 or CN7 pin 16, can be used also as a power supply output. The
current is limited by the maximum current capability of the U15 regulator (500 mA maximum concerning
STM32 Nucleo-64 board with shields consumption).
7.4.4 Internal power supply
The Nucleo-64 boards are designed to support two specific voltage configurations:
• VDD at 3.3 V configuration to reach the Nucleo-64 low-power mode
• VDD at 1.8 V configuration to demonstrate the MCU low-voltage capability
7.4.4.1 3V3
Regardless of the 5V power source, an LDO is used to deliver a fixed 3.3 V power voltage from 5V. The maximum
current capability of this source is 500 mA. To select the 3.3 V voltage for the VDD, set the JP5 jumper on [1‑2].
A solder bridge (SB8) is used to disconnect the LDO output when an external 3.3 V is applied to the Nucleo-64
board, to avoid backward voltage to 5V through this LDO.
• SB8 ON: U15 LDO output provides a 3.3 V power supply (default configuration).
• SB8 OFF: U15 LDO output does not provide 3.3 V. An external 3.3 V is needed.
7.4.4.2 1V8
An external SMPS can be used for the MCU to work at 1.8 V. The external SMPS capability is 400 mA maximum.
Before using the 1.8 V voltage, it is necessary to check that all interfaces connected to the Nucleo-64 board are
1.8 V compatible. To select the 1.8 V for the VDD, connect the VDD jumper (JP5) to the pin [2-3].
In this mode, it is possible to keep some MCU voltage domains on 3.3 V depending on the application use case.
The MCU voltage selection is done according to the solder bridge configuration. Refer to
configuration.
UM3062 - Rev 2
might power the board first from STLINK-V3EC, and the following risk
BUS
UM3062
Hardware layout and configuration
®
shield or an
Table 7 needs to be
Table 8 for solder bridge
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