Does this MCU MPC5646C need special power up sequence? VDD_HV applying first, or VDD_LV applying first, or don't care? Do we have a document to describe this requirement?
VDD_LV is not supposed to be supplied externally on this device. VDD_LV is generated by internal voltage regulator using external ballast transistor, so there's no need to do special power up sequence.
Is it allowed to use 5V for VDD_HV, and 3.3V on ballast transistor?
Thus the power dissipation on the ballast transistor will be less.
For this kind of case, should we power up 5V first or 3.3V first or don't care?
VDD_BV (supply of ballast transistor) can be independent of other supply voltages. It must be > 2.6V. So, 3.3V is OK. There are no power sequencing restrictions.
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