Rush current (in-rush current)
Beginner
The sudden rush of electricity when a switched-off part of the chip is turned back on.
Novice
The surge of current at wake-up, when a powered-off block’s internal capacitance charges back up. If every switch turns on at once, the surge can pull down the supply for neighboring blocks that are still working.
Expert
Limited by turning switches on in stages, for example through a daisy chain or in groups that wake one after another. The trade-off is peak current against wake-up time and the number of switch transistors.
Explained in Power planning (Design Flow).
See also: Power switch (header/footer), power gating.