Hardware layout and configuration
UM1879
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UM1879 Rev 4
10.2 Power
supply
The power supply is provided with four options:
–
ST-LINK/V2-1: CN1
–
CR2032 battery (not provided): CR1
–
External 5V: 5V_I
–
USB FS connector: USB USER CN7
•
ST-LINK/V2-1:
JP6 needs to be placed in position 3V3. JP3 is closed. JP5 is in position ON. CN3
jumpers are ON.
The STM32L476G Discovery board can be powered from the ST-LINK USB connector
CN1 (5V_USB_ST_LINK). Only the ST-LINK circuit has the power before the USB
enumeration, as the host PC only provides 100mA to the board at that time.
During the USB enumeration, the STM32L476 Discovery board requires 300 mA of
current to the host PC. If the host is able to provide the required power, the
STM32L476 is powered and the red LED LD2 is turned ON, thus the STM32L476
Discovery board and its extension board can consume no more than 300 mA current. If
the host is not able to provide the required current, the STM32L476 and the extension
board are not power supplied. As a consequence the red LED LD2 remains turned
OFF. In such case it is mandatory to use an external power supply, as explained in the
next section.
Warning:
If the maximum current consumption of the STM32L476
Discovery board and its extension board exceeds 300 mA, it
is mandatory to power the STM32L476 Discovery board using
an external power supply connected to 5V_I.
Note:
In case this board is powered by a USB charger or a USB battery connected on CN1, there
is no USB enumeration, the led LD2 remains OFF and the STM32L476 is not powered. In
this specific case only, fit the jumper JP2 to allow the STM32L476 to be powered anyway.
Remove this jumper JP2 if then a host PC is connected to the ST-LINK/V2-1 CN1 connector
to supply the board.
•
CR2032 battery inserted in CR1 (bottom side):
–
The CR2032 battery is not provided
–
JP6 needs to be placed in position BATT. JP3 is opened. JP5 is in position ON
–
The battery supplies the 3V3 and 3V power domains on board. All the peripherals
are powered, except the ST-LINK, which can only be supplied through the USB
connector CN1
•
External 5V_I or USB USER CN7 (USB FS connector):
–
External 5V_I: The pin 3 5V_I of P2 header can be used as input for an external
power supply. In this case, the STM32L476 Discovery board must be powered by
a power supply unit or by an auxiliary equipment complying with the standard EN-
60950-1: 2006+A11/2009, and must be Safety Extra Low Voltage (SELV) with a
limited power capability.
–
To use the USB USER CN7 to power supply the board, a jumper needs to be
placed between VUSB pin 4 and the pin 3 5V_I of P2 header (see
