Conflict driven scan chain configuration for high transition fault coverage and low test power

Two conflict-driven schemes and a new scan architecture based on them are presented to improve fault coverage of transition fault. They make full use of the advantages of broadside, skewed-load and enhanced scan testing, and eliminate the disadvantages of them, such as low coverage, fast global scan enable signal and hardware overhead. Test power is also a challenge for delay testing, so our method tries to reduce the test power at the same time. By the analysis of the functional dependency between test vectors in broadside testing and the shift dependency between vectors in the skewed-load testing, some scan cells are selected to operate in the enhanced scan and skewed-load scan mode, while others operate in traditional broadside mode. In the architecture, scan cells with common successors are divided into one chain. With the efficient conflict driven selection methods and partition of scan cells, fault coverage can be improved greatly and test power can be reduced, without sacrificing the test time and test data. Experimental results show that the fault coverage of the proposed method can reach the level of enhanced scan design.