Comparative study of CA with phase shifters and GLFSRs

In this paper, we investigate the use of Galois LFSRs (GLFSRs) as test pattern generators in BIST schemes that employ multiple scan chains. Current schemes use LFSRs or cellular automata (CA) with additional phase shifters to provide guaranteed minimum phase shifts between successive scan chains and also impose an upper bound on the number of taps for the XOR gate of each phase shifter. We compare CA with phase shifters (CAPSs) and GLFSRs without phase shifters in terms of the minimum inter-channel separation that they achieve and the overall XOR cost for each construction. Experimental results for different degrees show that GLFSRs are preferable in both hardware cost and fault coverage