An automatic test pattern generator for minimizing switching activity during scan testing activity

An automatic test pattern generation (ATPG) technique is proposed that reduces switching activity during testing of sequential circuits that have full scan. The objective is to permit safe and inexpensive testing of low-power circuits and bare dies that would otherwise require expensive heat removal equipment for testing at high speed. The approach works with standard scan designs that are commonly used and typically have significantly lower overhead than enhanced scan designs. The proposed ATPG exploits all possible "don\´t cares" that occur during scan shifting, test application, and response capture to minimize switching activity in the circuit under test. An ATPG that minimizes the number of state inputs that are assigned specific binary values has been developed. Don\´t cares at state inputs are assigned binary values that cause the minimum number of transitions during scan shifting and don\´t cares at primary inputs during scan shifting and capture are used to block gates that may have transitions during scan shifting. The proposed technique has been implemented and the generated tests are compared with those generated by a simple PODEM implementation for full scan versions of ISCAS89 benchmark circuits.