Enhanced LCCG: A novel test clock generation scheme for faster-than-at-speed delay testing

On-chip faster-than-at-speed delay testing provides a promising way for small delay defect detection. However, the frequency of on-chip generated test clock would be impacted by process variations. Hence, it requires determining the actual frequency of generated test clock to ensure the effectiveness of faster-than-at-speed delay testing. In this paper, we present a novel test clock generation scheme, namely Enhanced LCCG, for faster-than-at-speed delay testing. In the proposed scheme, faster-than-at-speed test clock is firstly generated by configuring the corresponding control information specified in the test pattern into Enhanced LCCG. Then, by constructing oscillation paths and counting the corresponding oscillation iteration numbers, the actual frequency of test clock can be measured and calculated with high resolution. Experimental results are presented to validate the proposed method.