Placement Density Aware Power Switch Planning Methodology for Power Gating Designs

Abstract

As advances in manufacture technology, leakage current increases dramatically in modern ICs. By turning off supply voltage in a low-power domain with power switches, power gating becomes a useful technique in resolving this problem. Since number and locations of power switches have great impact on chip area and IR-drop, an efficient and effective approach to insert power switches is required for the power gating designs. Unlike previous works using the greedy algorithm to handle this problem, this paper uses a simplified model to approximate required equivalent resistance of power switches in a low-power domain, and then determines number and types of power switches based on the value. In order to reduce impact on preplaced standard cells, we also propose a mathematical approach to find locations with less placement density to place power switches. The proposed methodology was integrated into a real-design flow. Experimental results demonstrate that our approach can insert less number of power switches and still satisfy the IR-drop constraint than other approaches.