In this mode, it is possible to keep some MCU voltage domain on 3V3 depending on the application use case.
The MCU voltage selection is done according to the solder bridge configuration. Refer to
configuration.
6.4.4.3
JP4 VDD voltage selection 1V8/3V3
The JP4 jumper selects the VDD voltage:
•
Set JP4 on [1-2] to set VDD to 3V3.
•
Set JP4 on [2-3] to set VDD to 1V8.
The current consumption on this jumper includes the MCU pin connected to VDD_MCU and the other features
supplied by VDD, such as the U9 level shifter supply pin for 1V8 STLINK-V3E compatibility and the LEDs.
The level shifter consumption is negligible according to correct SWD I/O settings to avoid an I/O floating level.
6.4.5
MCU power supply
To supply correctly the MCU, it is mandatory to configure the solder bridges as shown in
Table 9.
MCU power supplies
Solder bridge
configuration
MCU power supply
JP4 [1-2] / JP4 [2-3]
VDD selection: Jumper selection for VDD 3V3 / 1V8
JP5 [1-2] / ammeter
IDD: JP5 ON to supply the MCU or connected with an ammeter to do current measurement.
SB2 ON
SB for VDDSMPS input voltage
SB3 ON
SB for VREFP input voltage
SB30 ON
SB for VDDUSB input voltage
SB28 ON / SB29 OFF
SB for VDDIO2 PG[2-15] input voltage
SB28 ON / SB29 OFF: VDDIO follows 1V8 to 3V3 VDD_MCU.
SB28 OFF / SB29 ON: VDDIO fixed to 3V3 whatever the VDD-MCU voltage is.
SB50 ON
SB for VBAT input voltage
SB55 OFF / SB54 ON
SB for VDDA/VREF input voltage
SB55 ON / SB54 OFF: VDDA/VREF follows 1V8 to 3V3 VDD_MCU.
SB55 OFF / SB54 ON: VDDA/VREF fixed to 3V3 whatever the VDD-MCU voltage is.
For more detail about VDDA/VREFP power supply, refer to the MCU datasheet.
Warning:
1V8 voltage is given as an example, but the power on sequence implementation is not respected
when using 1V8 VDD. Refer to the application note STM32U5 Series hardware getting started
(
), and STM32U5xx products datasheets for power sequencing.
INTERNAL VCORE SMPS power supply
Power figures in run mode are significantly improved, by generating V
core
logic supply from the internal DC/DC
converter (this function is only available on '-Q' suffixed boards).
For all general information concerning design recommendations for STM32U5 with internal SMPS and design
guide for ultra
‑
low
‑
power applications with performance, refer to the application note
STM32U5 Series hardware
getting started
(
website.
UM2861
Power supply and power selection
UM2861
-
Rev 2
page 24/49
