Automatic synthesis and simulation of continuous-time ΣΔ modulators

This paper presents a mixed equation-based and simulation-based design methodology for continuous-time sigma-delta modulators from high level specifications down to layout. The calculation and scaling of the sigma-delta coefficients as well as circuit sizing and layout generation are implemented in the same analog design environment CAIRO+. The design of a complete third order current-mode continuous-time sigma-delta modulator is taken as an example to show the effectiveness of the proposed design methodology.