Local Merges for Effective Redundancy in Clock Networks

摘要

Process and environmental variations affect the reliability of clock networks. By synthesizing non-tree structures, the robustness of clock networks can be improved at the expense of higher capacitance. A cheap way of converting a tree structure to a non-tree structure is to insert cross links. Unfortunately, the robustness seems to improve only when the links are sufficiently short. Other non-tree structures such as meshes and multilevel fusion trees improve the robustness more effectively, but with much higher cost. In this work, we develop a new non-tree topology by merging a sub-clock tree with all other sub-clock trees that contain sequential elements that require strict synchronization. Results show that when compared with the state-of-the-art solutions, clock networks constructed with the proposed structure have similar capacitance but notable improved robustness. Moreover, the clock networks can satisfy tight skew constraints even when simulated under a more stringent variations model, with 22% lower capacitance when compared to solutions in earlier studies.