Integrated Power Distribution Network Synthesis for Mixed Macro Blocks and Standard Cells

Abstract

Power distribution network (PDN) requires more routing resources as wire resistance increases with technology scaling but IR drop constraint does not scale. We address post-placement PDN synthesis for mixed macro blocks and standard cells. Macro blocks already have partial PDN, while standard cells do not. So the design, which has been placed, is divided into a number of partitions: each macro block in its own partition, and standard cell area into a number of partitions. Multi-layer PDN synthesis is performed in each partition one by one; the goal of this problem is to insert minimum number of metal straps (in irregular pitches) while IR drop and electromigration (EM) constraints are respected. This is formulated as mixed integer quadratically constrained programming (MIQCP) and a heuristic algorithm is proposed for practical application. Experimental results with some test circuits indicate that the proposed approach achieves on average of 26% reduction in PDN straps, which helps reduce congestion overflow of signal routing by 15%, compared to popular approach in which PDN straps are located in regular pitch period.