An Efficient Physical Design of Fully-testable BDD-based Circuits

For the manufacturing test of ASICs, it is important to reach a high test coverage in order to get the defect level as low as possible. However, complex digital circuits are usually not fully testable. In order to address that, previous work suggested to realize the circuits by means of Binary Decisions Diagrams (BDDs). Here, each node is implemented using multiplexer gates (MUX gates) which, with some minor additions, yield 100% testable circuits, with respect to stuck-at and path delay faults. Unfortunately, current physical implementations of MUX gates are rather expensive with respect to propagation delay, power consumption, or transistor count. Hence, despite the prospect of gaining 100% testability, BDD-based circuits did not find significant attention yet. In this work, we propose an alternative realization of MUX gates based on pass transistor logic which addresses these drawbacks. Experiments show that this allows for the realization of fully testable BDD-based circuits which are competitive to or, in many cases, even better than state- of-the-art realizations.