Supplying The Board Through St-Link/V2-1 Usb Port; Using St-Link/2-1 Along With Powering Through The Cn18 Power Jack - ST STM32L4R9I-EVAL User Manual

Hardware layout and configuration
6.5.1

Supplying the board through ST-LINK/V2-1 USB port

To power STM32L4R9I-EVAL in this way, the USB host (a PC) gets connected with the
STM32L4R9I-EVAL board's Micro-B USB receptacle, via a USB cable. This event is the
beginning of the USB enumeration procedure. In its initial phase, the host's USB port
current supply capability is limited to 100 mA. It is enough because only the ST-LINK/V2-1
part of STM32L4R9I-EVAL draws power at that time. If the SB33 solder bridge is open, the
U22 ST890 power switch is set in the OFF position, which isolates the remainder of
STM32L4R9I-EVAL from the power source. In the next phase of the enumeration
procedure, the host PC informs the ST-LINK/V2-1 facility of its capability to supply up to 300
mA of current. If the answer is positive, the ST-LINK/V2-1 sets the U22 ST890 switch to ON
position to supply power to the remainder of the STM32L4R9I-EVAL board. If the PC USB
port is not capable of supplying up to 300 mA of current, the CN18 power jack is available to
supply the board.
If a short-circuit occurs on the board, the ST890 power switch protects the USB port of the
host PC against a current exceeding 600 mA. In such an event, the LD8 LED lights on.
The STM32L4R9I-EVAL board is also supply-able from a USB power source not supporting
enumeration, such as a USB charger, as shown in
power switch ON regardless of the enumeration procedure result and passes the power
unconditionally to the board.
The LD7 red LED turns on whenever the whole board is powered.
6.5.2

Using ST-LINK/2-1 along with powering through the CN18 power jack

If the board requires more than 300 mA of supply current, this cannot be provided by the
host PC connected to the ST-LINK/2-1 USB port, used for debugging or flashing
STM32L4R9AII6. In such a case, the board is supplied through CN18 (marked PSU_DC5V
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 in JP11 header in E5V position,
2. Connect the external 5 V power source to CN18,
3. Check the red LED LD7 is turned on,
4. Connect the host PC to the CN12 USB connector.
In case the board requires more than 300 mA and the host PC is connected via USB before
the board is powered from CN18, there is a risk of the following events to occur, in the order
of severity:
1. The host PC is capable of supplying 300 mA (the enumeration succeeds) but it does
not incorporate any over-current protection on its USB port. It is damaged due to over-
current.
2. The host PC is capable of supplying 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 requirement from STM32L4R9I-EVAL is
detected. This causes an operating failure to STM32L4R9I-EVAL.
3. The host PC is not capable of supplying 300 mA (the enumeration fails) so ST-LINK/V2-
1 does not supply the remainder of STM32L4R9I-EVAL from its USB port V
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Table
UM2248 Rev 4
4. ST-LINK/V2-1 turns the ST890
UM2248
line.
BUS