Multiple scan chains for power minimization during test application in sequential circuits

The paper presents a novel technique for power minimization during test application in sequential circuits using multiple scan chains. The technique is based on a new design for test architecture and a novel test application strategy which reduces spurious transitions in the circuit under test. To facilitate the reduction of spurious transitions, the proposed design for test architecture is based on classifying scan latches into compatible, incompatible and independent scan latches. Based on their classification, the scan latches are partitioned into multiple scan chains and a single extra test vector associated with each scan chain is computed. A new test application strategy which applies the extra test vector to primary inputs while shifting out test responses for each scan chain, minimizes power dissipation by eliminating the spurious transitions which occur in the combinational part of the circuit. The newly introduced multiple scan chain-based technique does not introduce performance degradation and minimizes clock tree power dissipation with minimal impact on both test area and test data overhead. Unlike previous approaches which are test set dependent, and hence are not able to handle large circuits due to the complexity of the design space, the paper shows that with low test area and test data overhead substantial savings in power dissipation during test application are achieved in very low computational time for both small and large test sets. For example, in the case of the benchmark circuit s15850, it takes <6009 in computational time and <1 percent in test area and test data overhead to achieve over 80 percent savings in power dissipation.