Supplying The Board Through The Stlink-V3E Usb Port; Using Stlink-V3E Along With Powering Through The Cn25 Power Jack - ST STM32G474E-EVAL User Manual

UM2514
5.3.1

Supplying the board through the STLINK-V3E USB port

To power the STM32G474E-EVAL board, the USB host (a PC) gets connected to the Micro-
B USB receptacle of the STM32G474E-EVAL board via a USB cable. The connection event
starts the USB enumeration procedure. In its initial phase, the current supply capability of
the USB port on the host is limited to 100 mA. It is enough because only the STLINK-V3E
part of the STM32G474E-EVAL draws power at that time: the U25 STMPS2151 power
switch is set to the OFF position, which isolates the rest of the STM32G474E-EVAL from the
power source. In the next phase of the enumeration procedure, the host PC informs the
STLINK-V3E facility of its capability to supply current up to 300 mA. If the answer is positive,
the STLINK-V3E sets the U25 STMPS2151 switch to the ON position to supply power to the
rest of the STM32G474E-EVAL board. If the PC USB port is not capable of supplying
current up to 300 mA, the CN25 power jack is available to supply the board.
If a short circuit occurs on the board, the STMPS2151 power switch protects the USB port of
the host PC against a current demand exceeding 500 mA. In such an event, the LD7 LED
lights up.
The STM32G474E-EVAL board can also be supplied from a USB power source not
supporting enumeration, such as a USB charger. In this particular case, jumper JP12 must
be fitted with a jumper hat as shown in
regardless of the enumeration procedure result and passes the power unconditionally to the
board.
The LD6 green LED turns on whenever the whole board is powered.
5.3.2

Using STLINK-V3E along with powering through the CN25 power jack

When the board requires a current higher than 300 mA, the host PC, connected to the
STLINK-V3E USB port for debugging or programming, cannot supply the
STM32G474QET6 MCU. In such a case, the board can be powered through CN25 (marked
PSU on the board).
To do this, it is important to power the board before connecting it with the host PC, which
requires the following sequence to be respected:
1. Set the jumper JP12 in the E5V position.
2. Connect the external power source to CN25.
3. Check that the green LED LD6 is turned on.
4. Connect the host PC to the CN21 USB connector.
Caution: In case the board requires more than 300 mA and the host PC is connected via USB before
the board is powered from CN25, the following risk events are possible (listed in reverse
severity order):
1. The host PC can supply 300 mA (the enumeration succeeds) but it features no over-
current protection on its USB port. It is damaged due to over-current.
2. The host PC can supply 300 mA (the enumeration succeeds) and it has built-in
over-current protection on its USB port, limiting or shutting down the power out of its
USB port when the excessive current demand from the STM32G474E-EVAL is
detected. This causes an operating failure of the STM32G474E-EVAL.
3. The host PC cannot supply 300 mA (the enumeration fails). The STLINK-V3E does not
supply the rest of the STM32G474E-EVAL from its USB port V
Table 5 details the jumper and solder bridge settings used for the configuration of the power
supply of the STM32G474E-EVAL.
Table 5. STLINK-V3E bypasses STMPS2151 power
UM2514 Rev 5
Hardware layout and configuration
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