8.1 Power-Up Considerations
VDDIO and VDDIN must rise simultaneously, prior to VDDCORE, VDDPLL, and VDDUTMIC rising. This is respected if VDDCORE, VDDPLL, and VDDUTMIC are supplied by the embedded voltage regulator.
If VDDCORE is powered by an external voltage regulator, VDDIO and VDDIN must reach their minimum operating voltage before VDDCORE has reached VDDCOREmin.
If VDDCORE rises at the same time as VDDIO and VDDIN, the minimum and maximum rising slopes of VDDIO and VDDIN must be respected. For additional information, see DC Characteristics.
To prevent any overcurrent at power-up, it is required that VREFP rises simultaneously with VDDIO and VDDIN.