Hardware layout and configuration
UM1902
12/79
DocID027916 Rev 2
5.2 Power
supply
STM32746G-EVAL evaluation board is designed to be powered by 5 V DC power supply
and it is protected by PolyZen from wrong power plug-in event. It is possible to configure the
evaluation board to use any of the following six sources for the power supply:
•
5 V DC power adapter connected on the board to the power jack CN17, the power jack
on the board (Power Supply Unit on silk screen of JP13 (PSU)). This is default setting
of power supply source selection on STM32746G-EVAL evaluation board.
•
5 V DC power with 300 mA limitation from CN21, the USB type B connector of
ST-LINK/V2-1 (USB 5 V power source on silkscreen of JP13 (STlk)). If the USB
enumeration succeeds (as explained below), the ST-LINK/V2-1 U5V power is enabled,
by asserting the PWR_EN pin. This pin is connected to a power switch (ST890), which
powers the board. This power switch features also a current limitation to protect the PC
in case of short-circuit on board. If an overcurrent (more than 600 mA) happens on the
board, the LED LD11 is lit. This setting cannot be used as default power source
selection, because the whole board power consumption will be larger than the current
limitation of DC power from CN21.
•
5V DC power with 500 mA limitation from CN8, the USB OTG HS Micro-AB connector
(USB 5V power source on silkscreen of JP13 (HS)).
•
5V DC power with 500 mA limitation from CN13, the USB OTG FS1 Micro-AB
connector (USB 5V power source on silkscreen of JP13 (FS1)).
•
5V DC power with 500 mA limitation from CN14, the USB OTG FS2 Micro-AB
connector (USB 5V power source on silkscreen of JP13 (FS2)).
•
5V DC power from CN5 and CN6, the extension connectors for daughterboard
(daughterboard power source on silkscreen of JP13 (D5V)).
STM32746G-EVAL evaluation board can be powered from ST-LINK/V2-1 USB connector
CN21 (U5V), only when the 5.7" LCD is disconnected, otherwise power consumption
exceeds 300mA. When the board is connected to USB port only the ST-LINK/V2-1 is
powered for the USB enumeration, because host PC only provides 100 mA max to the
board at that time. During the USB enumeration, STM32746G-EVAL board requires 300 mA
power from the host PC. If the host PC is able to provide the required power, the
enumeration succeeds and the power transistor U17 (ST890) is switched ON, the red LED
LD10 is turned ON, thus STM32746G-EVAL evaluation board can consume no more than
300 mA of current. If the host PC is not able to provide the requested current, the
enumeration fails. Therefore the ST890 (U17) remains OFF so consequently 3.3 V domain
of the board and STM32 will not be powered. As a consequence, the red LED LD10 remains
turned OFF. In this case it is mandatory to use an external power supply as extra power
supply.
E5V (from PSU) or D5V must be used as external power supply, in case current
consumption of STM32746G-EVAL evaluation board exceeds the allowed current on USB.
In this condition it is still possible to use USB for communication, for programming or
debugging only, but it is mandatory to power the board, first using E5V or D5V, then
connecting the USB cable to the PC. Proceeding this way ensures that the enumeration
succeeds, thanks to the external power source.
