X-Sources Analysis for Improving the Test Quality

Achieving very high test coverage (e.g. 99.9% stuck-at fault model) is becoming a standard for ICs used in the high reliable systems like automotive vehicle. X-sources (unknown value sources) are one of the common root causes preventing designs from achieving the test coverage goal. The paper first summarizes common X-sources in industry designs. A novel approach is then proposed to systematically identify and analyze all of the X-sources that impacts the test coverage most with accurate estimation by utilizing the Automatic Test Pattern Generator (ATPG). Consequently, users are able to take the analysis result and make necessary and minimum changes to eliminate Xs to achieve the test quality goal effectively.