6.4.4
Internal power supply
NUCLEO board are designed to support two specific voltage configuration:
•
3V3 MCU configuration to reach NUCLEO low-power mode
•
1V8 MCU configuration to demonstrate MCU low-voltage capability
6.4.4.1
3V3
Regardless of the 5V power source, an LDO is used to switch from 5V to the default power source of the
VDD_MCU: 3V3. The maximum current capability of this source is 500 mA. To select the 3V3 voltage for the
VDD_MCU, connect the Jumper JP4 to pin [1-2].
6.4.4.2
1V8
An external SMPS is used for the MCU to work at 1V8. This helps to reduce max power consumption. The
external SMPS capability is 400 mA. This power supply must be reserved only for the VDD_MCU. To select the
1V8 voltage for the VDD_MCU, connect the Jumper JP4 to pin [2-3].
6.4.4.3
Internal V
core
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 STM32L5 with INTERNAL SMPS, and design
guide for ultra-low-power applications with performance, refer to L5 Hardware Getting started (AN5211) at the
6.5
LEDs
User LD1
A green user LED is connected to the STM32 I/O PA5 (SB120 ON and SB118 OFF, optional configuration
corresponding to the ST Zio D13) or PC7 (SB120 OFF and SB118 ON, default configuration). A transistor is used
to drive the LED when the I/O voltage is 1V8.
User LD2
A blue user LED is connected to PB7. A transistor is used to drive the LED when the I/O voltage is 1V8.
User LD3
A red user LED is connected to PA9. A transistor is used to drive the LED when the I/O voltage is 1V8.
These user LEDs are ON when the I/O is HIGH value, and are OFF when the I/O is LOW.
LD4 COM
The tricolor LED LD4 (green, orange and red) provides information about ST-LINK communication status. The
LD4 default color is red. LD4 turns to green to indicate that the communication is in progress between the PC and
the ST-LINK/V2-1, with the following setup:
•
Slow blinking red/off: at power-on before USB initialization
•
Fast blinking red/off: after the first correct communication between PC and ST-LINK/V2-1 (enumeration)
•
Red LED ON: when the initialization between the PC and ST-LINK/V2-1 is complete
•
Green LED ON: after a successful target communication initialization
•
Blinking red/green: during communication with the target
•
Green ON: communication finished and successful
•
Orange ON: communication failure
LD5 ST-LINK USB power switch fault
LD5 indicates that the board power consumption on USB exceeds 500 mA. Consequently, the user must power
the board with an external power supply.
UM2581
LEDs
UM2581
-
Rev 2
page 22/48