ok ....In the case of micro-controller ( especially high end ) Have various interfaces like their peripheral voltage is say 3.3 v they have core working at 1.2 v and it can be connected to DDR2 ram which works on 1.8 v ....so while powering -up such a micro-controller ..... There exits a sequence from which you need to give the power to IC..... Like 1.2 v Core voltage first then after 100 usec you need to give 1.8v and after 250 us you need to give peripheral voltage..... this is generally specified by the manufacture of the IC......and they generally explain this in the term of waveform.... One need to study this before choosing the right component and power section design for Micro-controller....In the IC that you are using I think don't have power sequence....I searched it in the datasheet....