Good news - the datasheet is fantastically detailed (and in many places utter gobbledegook to me
)
DCDC1 is an internal switching boost converter which only affects 3 or 4 pins and relies on a relatively small amount of external components.
See the attached section of the block diagram (pictures,yay!).
Moreover, there is quite a clever power up/power down sequence. Correct functioning of DCDC1 is tested early on so if not regulating properly the chip will stop the power up sequence and shutdown nicely - thus protecting the other circuitry.
So either the internal MOSFET is burned, one of the support components for the boost converter has failed or there is insufficient voltage on the supply, I think
.