The VDDIO external reference voltage pin is available on pin header P11. This is for external voltage input and sets the reference voltage level for the General-Purpose Input/Output (GPIO)s and the TWI.
If using external VDDIO supply on P11, disconnect the VDDIO input jumper on P18. See further details in VDDIO reference voltage.
VDDIO is shown in TWI configuration.
Note: The minimum VDDIO voltage is 1.7 V. Any lower
voltage can result in lost TWI communication between host and the nPM1304
Power Management Integrated Circuit (PMIC).