Method and algorithm for functional critical paths selection and critical path sensors and controller insertion

Abstract

CAD software examines delays of paths in a design from design engineers and first selects the longest paths. Then all paths that converge with these longest paths are examined for delays, and a fastest converging path is selected for each of the longest paths. The longest paths are again sorted by the fastest converging delay, and paths with slower converging paths are selected to be Functional Critical Paths (FCP's). Functional critical path timing sensors are added to each FCP to test setup time with an added margin delay. When the margined path delays fail to meet setup requirements, the functional critical path timing sensors signal a controller to increase VDD. When no failures occur over a period of time, the controller decreases VDD. The CAD software can replicate some of the FCP's and add toggle pattern generators and timing sensors and a margin controller to adjust the margin delay.