6.4.4.2 1V8
An external SMPS can be used for the MCU to work at 1.8 V. The external SMPS capability is 400mA maximum.
Before using the 1.8 V voltage, it is necessary to check that all interfaces connected to the Nucleo-144 board are
1.8 V compatible. To select the 1.8 V for the VDD, set the VDD jumper (JP4) on [2-3].
In this mode, it is possible to keep some MCU voltage domain at 3V3 depending on the application use case.
The MCU voltage selection is done according to the solder bridge configuration. Refer to Table 9 for solder bridge
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 consumption on this jumper includes the MCU power pins connected to the VDD_MCU power line and the
other features supplied by VDD, such as the level shifter power supply pins for STLINK-V3E, the user button, the
ARDUINO
®
shield on the IOREF pin, and power supply pins on the ST morpho connector.
6.4.5 MCU power supply
The default configuration of the MCU power pins is described in Table 9.
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
I
DD
: JP5 ON to supply the MCU or connected with an ammeter to do the 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: On this Nucleo-144, the power
‑
on sequence implementation for the 1.8 V use case is
given as an example and might not follow the recommended power
‑
on sequencing. Refer
to the application note Getting started with STM32U575/585 MCU hardware development
(AN5373) and STM32U5xx products datasheets for power on sequencing.
INTERNAL VCORE SMPS power supply
Power figures in run mode are significantly improved, by generating a 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 Getting started with
STM32U575/585 MCU hardware development (AN5373) at the www.st.com website.
UM2861
Power supply and power selection
UM2861 - Rev 5
page 23/49
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