UM2408 Rev 2 25/51
UM2408 Hardware layout and configuration
50
 
If a deadlock is faced due to a mismatch between the HW 
board setting and the FW setting (LDO/SMPS), the user can 
recover the board by doing the following:  
- Power off the board 
- Connect CN11 ‘BT0’ pin (BOOT0) to VDD using a wire 
- This changes the BOOT0 pin to 1 instead of 0 and thus the 
device boot address is changed to boot address 1 making the 
bootloader starting in System memory, instead of starting the 
FW in the user Flash (FW that is setting a wrong LDO/SMPS 
configuration) 
- Power on the board and connect using 
STM32CubeProgrammer 
- Erase the user Flash 
- Power off the board and remove the wire between BOOT0 
and VDD 
- The board is now recovered and can proceed normally.
6.4.9  JP5: 1.8 V / 3.3 V selection
JP5, labeled "VDD_MCU" is used to select the VDD supply for the MCU:
• Jumper JP5 pin 1-2: VDD_MCU = 3.3 V (Default configuration)
• Jumper JP5 pin 2-3: VDD_MCU = 1.8 V
6.5  External SMPS selection
The user can connect an external SMPS to the CN6 footprint (For example 
ST1PS02D1QTR).
CN6 pin-out is described in Table 11.
 
Table 11. External SMPS selection 
CN6 pin Pin name Function
Configuration when 
using an external 
module connected to 
CN6
CN6 Pin 1 3V3_VDD 3.3V VDD supply for MCU -
CN6 Pin 2 SMPS_V1 (PG8)
External SMPS output voltage 
selection “D1”
(1)
SB34 ON / SB31 OFF
CN6 pin 3 VOUTVDD
External 3.3V VDD supply for 
MCU
-
CN6 Pin 4 SMPS_EN  (PG9) External SMPS Enable “EN”
(1)
SB35 ON / SB41 OFF
CN6 pin 5 1V2_VOUTCORE
External SMPS 1.2V or external 
power supply providing 1.2V for 
MCU VCORE (VCAP pins)
-
CN6 Pin 6 SMPS_SW  (PG10)
External SMPS Enable for the 
auxiliary output voltage “AUX”
(1)
SB33 ON / SB30 OFF
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