Noise Considerations in Circuit Optimization

        Noise can cause digital circuits to switch incorrectly and thus produce spurious results. It can also have adverse power, timing and reliability effects. Dynamic logic is particularly susceptible to charge-sharing and coupling noise. Thus the design and optimization of a circuit should take noise considerations into account. Such considerations are typically stated as semi-infinite constraints in the time-domain. Semi infinite problems are generally harder to solve than standard nonlinear optimization problems. Moreover, the number of signals to be checked and the number of sub-intervals of time during which the checking must be performed can potentially be very large. Thus, the practical and realistic incorporation of noise constraints during circuit optimization is a hitherto unsolved problem.

        This paper describes a novel method for incorporating noise considerations during automatic circuit optimization. Semi-infinite constraints representing noise considerations are first converted to ordinary equality constraints involving time integrals, which are readily computed in the context of circuit optimization based on time-domain simulation. The gradients of these integrals are computed by the adjoint method. By using an augmented Lagrangian optimization merit function, the adjoint method is applied to compute all the necessary gradients required for optimization in a single adjoint analysis, no matter how many noise measurements are considered and irrespective of the dimesionality of the problem. The technique is applicable in both dynamic and static circuit optimization contexts. Numerical results are presented in the dynamic case.

By: Chandu Visweswariah, Ruud A. Haring, Andrew R. Conn

Published in: RC21505 in 1999


This Research Report is available. This report has been submitted for publication outside of IBM and will probably be copyrighted if accepted for publication. It has been issued as a Research Report for early dissemination of its contents. In view of the transfer of copyright to the outside publisher, its distribution outside of IBM prior to publication should be limited to peer communications and specific requests. After outside publication, requests should be filled only by reprints or legally obtained copies of the article (e.g., payment of royalties). I have read and understand this notice and am a member of the scientific community outside or inside of IBM seeking a single copy only.


Questions about this service can be mailed to .