An Efficient Test Pattern Generation Scheme for an On Chip BIST

Testing and power consumption are becoming two critical issues in VLSI design due to the growing complexity of VLSI circuits and remarkable success and growth of low power applications (viz. portable consumer electronics and space applications). On chip Built In Self Test (BIST) is a cost-effective test methodology for highly complex VLSI devices like Systems On Chip. This paper deals with cost-effective Test Pattern Generation (TPG) schemes in BIST. We present a novel methodology based on the use of a suitable Linear Feedback Shift Register (LFSR) which cycles through the required sequences (test vectors) aiming at a desired fault coverage causing minimum circuit toggling and hence low power consumption while testing. The proposed technique uses circuit simulation data for modeling. We show how to identify the LFSR using graph theory techniques and compute its feedback coefficients (i.e., its characteristic polynomial) for realization of a Test Pattern Generator.