Power distribution has two problems that are, sizing wires and power distribution network. As can be seen from below figure, the branch carry the currents in all branches. If the logic gates use few standard transistor sizes, computing power in a line is challenging. In order to design large integrated circuits, simple rules are chosen for power supply widths. Hence, Metal migration is the problem in power supply distribu¬tion. In order to reduce the power supply noise, capacitors across the power supply pins are used in printed circuit board design. Further, in large size integrated circuits the decoupling capacitors are used in the semiconductor chips. Therefore, in microprocessor integrated circuits to add decou¬pling capacitance a separate chip is bonded on top of the integrated circuit.
Fig_Power Distribution Techniques