Low Power Clock Buffer Planning Methodology in F-D Placement for Large Scale Circuit Design∗

Abstract — Traditionally, clock network layout is performed after cell placement. Such methodology is facing a serious problem in nanometer IC designs where people tend to use huge clock buffers for robust-ness against variations. That is, clock buffers are often placed far from ideal locations to avoid overlap with logic cells. As a result, both power dissipation and timing are degraded. In order to solve this problem, we propose a low power clock buffer planning method-ology which is integrated with cell placement. A Bin-Divided Grouping algorithm is developed to construct virtual buffer tree, which can explicitly model the clock buffers in placement. The virtual buffer tree is dynamically updated during the placement to re-flect the changes of latch locations. To reduce power dissipation, latch clumping is incorporated with the clock buffer planning. The experimental results show that our method can reduce clock power significantly by 21 % on average. I