\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.