Obstacle-avoiding and slew-constrained buffered clock tree synthesis for skew optimization

Abstract

Buered clock tree synthesis (CTS) is increasingly critical as VLSI technology continually scales down. Many researches have been done on this topic due to its key role in CTS, but current approaches either lack the obstacle-avoiding functionality or lead to large clock latency and/or skew. This paper presents a new obstacle-avoiding CTS approach with separate clock tree construction and buer insertion stages based on an integral view to explore the global optimization space. Aiming at skew optimization under constraints of slew and obstacles, our CTS approach features the clock tree construction stage with the obstacle-aware topology generation algorithm called OBB, balanced insertion of candidate buer positions, and a fast heuristic buer insertion algorithm. Experimental results show the eectiveness of our CTS approach with significantly improved skew and latency than [6] by 46% and 63% on average, and 15.3% reduction in skew than [5]. Our OBB heuristic obtains 36% improvement in skew than the classic balanced bipartition algorithm (BB) in [10].