\section{Introduction}\label{sec:intro}

Analysing the Robustness of Surfing Circuits

Suwen Yang and Mark R. Greenstreet
Workshop on Formal Verification of Analog Circuits (FVAC'2005)

We consider the robustness of surfing circuits. Surfing is a technique for implementing high-speed digital pipelines that exploits the analog dynamics of the underlying circuits. Thus, verification must consider the analog behaviour of the design. We first give a description of surfing. We then presents a method for analysing the sensitivity of surfing circuits to small-signal disturbances by approximating the continuous time system as a sampled-time one and computing the eigenvalues of the appropriate sensitivity matrix. We briefly sketch results from using our approach. We go on to show how the small-signal analysis provides a basis for exploring large-scale, non-linear behaviours by examining the noise margins of our circuits. Circuits such as flip-flops, sense amplifiers and synchronizers can exhibit metastability failures that are undetectable given the numerical accuracy limitations of simulators such as HSPICE. We present a novel simulation technique that allows us to generate accurate waveforms for the metastability failures and similar events. We apply our method to two latches and a self-resetting circuit for clock-phase generation.