Robust chip-level clock tree synthesis for SOC designs

A key problem that arises in System-on-a-Chip (SOC) designs of today is the Chip-level Clock Tree Synthesis (CCTS). CCTS is done by merging all the clock trees belonging to different IPs per chip specifications. A primary requirement of CCTS is to balance the sub-clock-trees belonging to different IPs such that the entire tree has a small skew across all process corners. This helps in timing closure across all the design corners. Another important requirement of CCTS is to reduce clock divergence between IPs that have critical timing paths between them, thereby reducing maximum possible clock skew in the critical paths and thus improves yield. In this work, we propose effective CCTS algorithms to simultaneously reduce multi-corner skew and clock divergence. To the best of our knowledge, this is the first work that attempts to solve this practically important problem. Experimental results on several testcases indicate that our methods achieve 10%-31%(20% on average) clock divergence reduction and between 16--64ps skew reduction (1.6%-6.4% of cycle time for a 1GHz clock) with less than 0.5% increase in buffer area/wirelength compared to existing CTS algorithms.