Integrated design & test: Conquering the conflicting requirements of low-power, variation-tolerance and test cost

Design objectives of robustness and low-power usually do not go hand in hand with the test objectives of maximum test coverage and minimum test cost. Low power robust design techniques such as dual-Vth, dual-VDD, or adaptive body biasing have negative impact on the associated test cost. Similarly, test techniques like enhanced scan have large overhead in terms of area and power. In this paper, we try to mitigate the conflicting design and test requirements using an integrated approach to design and test that utilizes the existing low power and error resilient design techniques and augments them to improve test coverage and cost. Simulation results on an example 8x8 Wallace tree multiplier in 90nm technology node show 20% reduction in operating power, 60% reduction in test power and 99% reduction in critical paths while at the same time improving the yield from 96% to 100%, compared to existing design and test methodologies. All this comes at the cost of a marginal increase in area (7.8%).