A CAD approach for pre-layout optimal PDN design and its post-layout verification

Abstract

Design of power distribution network (PDN) draws great attention to integrated circuit (IC) designers as it directly affects the circuit performance. The challenge is to immune the circuit from the noise arising due to PDN by means of effective placement of decoupling capacitance (decap) with optimal power, delay, energy and area utilization. Our work involves extraction of circuit parameters in the pre-layout stage and estimating decoupling capacitance as an early prediction activity based on dynamic power dissipation. We propose a new modular pre-layout PDN (MPLPDN) design approach, which modularizes the circuit and involves a computer aided design (CAD) methodology to investigate the changes in noise, power and delay parameter based on predictive decap allocation across the modules. A pruning methodology has been adopted to choose the best combination of the modules. The modularization algorithm is applied in a bottom up approach i.e. the lower level modules are combined at first and the top level module is created at the last stage. The experimental results based on pre and post layout simulation of application circuits show that MPLPDN achieves a considerable PDN noise suppression with a negligible increase in power, delay, energy and area. The comparison between pre-layout and post-layout simulation results also establishes the correctness of our early prediction.