Testing of differential cascode voltage switch one-count generators

摘要

Clocked differential cascode voltage switch (DCVS) circuits are dynamic CMOS circuits which can implement both inverting and noninverting functions. They have protection against test-set invalidation due to timing skews at the inputs and circuit delays as well as due to charge distribution. The problem of detecting stuck-at, stuck-open, and stuck-on faults in DCVS implementations of one-count generators is considered. A one-count generator counts the number of ones in its inputs. It is made up of full adders and half-adders. If the number of inputs to the one-count generator is n, then the number of outputs k is given by (log/sub 2/(n+1)). For a maximal DCVS one-count generator, for which n=2/sup k/-1, it is shown that the size of the test set is only four. For a nonmaximal DCVS one-count generator, for which n not=2/sup k/-1, the upper bound on the size of the test set is 5(K-1), in other words, the size is O(log/sub 2). For a DCVS ripple-carry adder, which forms a part of the DCVS one-count generator, the test-set size is four.