Effective Decap Insertion in Area-Array SoC Floorplan Design

Abstract

As VLSI technology enters the nanometer era, supply voltages continue to drop due to the reduction of power dissipation, but it makes power integrity problems even worse. Employing decoupling capacitances (decaps) in floorplan stage is a common approach to alleviating supply noise problems. Previous researches overestimate the decap budget and do not fully utilize the empty space of the floorplan. A floorplan usually has a lot of available space that can be used to insert the decap without increasing the floorplan area. Therefore, the goal of this work is to develop a better model to calculate the required decap to solve the power supply noise problem in area-array based designs, and increase the usage of available space in the floorplan to reduce the area overhead caused by decap insertion. The experimental results of this work are encouraging. Compared with previous approaches, our methodology reduces 38% of the decap budget in average for MCNC benchmarks but can still meet the power supply noise requirements. The final floorplan areas with decap are also smaller than the numbers reported in previous works.