Described is an apparatus which comprises: a plurality of transistors coupled to an input power supply and to a load; a first comparator with a first node coupled to the load, and a second node coupled to a first reference; a second comparator with a first node coupled to the load, and a second node coupled to a second reference, the second reference being different from the first reference; and a logic unit to receive output of the first comparator and output of the second comparator, the logic unit to turn on or off transistors of the plurality of transistors according to outputs of the first and second comparators.