Power

The STM32L4R9I-EVAL board requires 5 VDC to operate and offers several possibilities to supply this:
  1. ST-Link/V2-1 USB port
  2. Power jack (centre pin is plus)
  3. USB OTG port
  4. Daughterboard
Jumper JP11 (labelled ‘5V source’) selects the supply input. Default is the first option (position 3 ‘STlk’), which is logical as that is what you would use once you have unpacked the board and want to try it out for the first time.

The power jack input of the STM32L4R9I-EVAL

is intended for applications requiring 300 mA or more, which most PC USB ports either cannot supply or should not supply as they are lacking the necessary current limiting to protect the computer. Note that for power-hungry applications a heatsink can be fitted on the MCU as the board provides mounting holes for this.


close up of display mb1314

To power the board through the USB OTG connector jumper JP11 must be placed at position ‘U5V’.
JP11 position ‘D5V’ is used when either the board must be powered by a daughter board or when the 5-volt supply must be routed to the daughter board. So if your application uses a daughter board without its own supply JP11 should have two jumpers on it.

MCU power

Besides JP11 the board features several jumpers to configure the various MCU’s supply pins:
  • With JP10 the MCU’s VDD power pins can be connected to either a fixed 3V3 supply or to a variable supply (1.71 to 3.6 V) adjustable with RV3.
  • JP1 determines the source for the MCU’s VDDUSB terminal,
  • JP2 does this for the VDDA terminal
  • and JP3 for the VDDIO2 pins.

Current consumption of the MCU (IDD) can be measured in run and low-power modes (except for shutdown mode). It is the MFX together with dedicated circuitry that allows this (JP4 enables or bypasses this circuitry).