Computer-aided tolerance/correlation design of integrated circuits

The problem of computer-aided tolerance design is extended to include the assignment of correlation coefficients between integrated circuit elements, in addition to assigning the tolerances of the elements, in order to achieve a desired circuit response variability. An algorithm for tolerance/correlation design is presented in which an objective function is minimized in order to achieve design objectives. Constraint equations are included in the objective function to keep the correlation coefficient matrix positive definite during adjustment of the correlation coefficients. The algorithm is tested using two practical integrated circuits.