If the power supply is 3V3 or 5V, the ST-LINK is not powered and cannot be used.
1) Power supply input from STLINK-V3E USB connector (default setting)
The STM32G4 Nucleo-32 board and shield can be powered from STLINK-V3E connector CN1 (5 V).
If the USB enumeration succeeds, the 5V_USB_STLK power is enabled, by asserting the T_PWR_EN signal from
STM32F723IEK6 "STLINK V3" (U5). This pin is connected to a power switch STMPS2151STR (U7), which
powers the board. The power switch STMPS2151STR (U7) features also a current limitation to protect the PC in
case of short-circuit on board. If an overcurrent (more than 500 mA) happens on board, the red LED LD3 (OC as
Over Current) is lit.
The Nucleo board and its shield can be powered from ST-LINK USB connector CN1, but only ST-LINK circuit gets
power before USB enumeration, because the host PC only provides 100 mA to the board at that time.
During the USB enumeration, the Nucleo board requires 500 mA power from the host PC.
•
If the host is able to provide the required power, the enumeration finishes by a
SetConfiguration
command.
Then, the power switch STMPS2151STR is switched ON, the green LED LD4 (5V_PWR) is turned ON, thus
Nucleo board and its shield on it can consume 500 mA at the maximum.
•
If the host is not able to provide the requested current, the enumeration fails. Therefore, the
STMPS2151STR power switch (U7) remains OFF and the MCU part including the extension board is not
powered. Therefore, the green LED LD4 remains turned OFF. In this case, it is mandatory to use an external
power supply.
Caution:
If the maximum current consumption of the STM32G4 Nucleo-32 board and its shield boards exceeds 300 mA, it
is either mandatory to check the root cause of the overconsumption, and consequently (if needed) to power the
STM32G4 Nucleo-32 board with an external power supply connected to VIN, 5V or 3V3.
2) External power supply input from USB charger (5 V)
In case a USB charger powers the board, there is no USB enumeration. The target is powered anyway.
3) External power supply input from VIN (7 V - 12 V, 800 mA max)
The STM32G4 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 cases are summarized in
Table 5.
External power sources: VIN (7 V - 12 V)
Input power
name
Connector
pins
Voltage range
Maximum
current
Limitation
VIN
CN3 pin 1
7 V to 12 V
800 mA
From 7 V 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
•
250 mA input current when 9 V < VIN < 12 V
4) External power supply input from external 3.3 V
When a shield board provides the 3.3 V, it is interesting to use the 3V3 (CN3 pin 14) directly as power input (refer
to Table 4). In this case, the programming and debugging features are not available, since the ST-LINK is not
powered.
Table 6.
External power sources: 3V3
Input power name
Connector pins
Voltage range
Maximum current
3V3
CN3 pin 14
3 V to 3.6 V
1.3 A
UM2397
Power supply
UM2397
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Rev 2
page 13/30
