DISCO: a graphical methodology for the design of Sigma-Delta modulators

Abstract

A MATLABTM toolbox for the design and simulation of continuous time (CT) and discrete time Sigma-Delta modulators is presented. The design of Sigma-Delta modulators is performed by placing the poles and zeros of the loop filter and estimating the resulting noise transfer function and signal transfer function. For this, the toolbox offers a graphical user interface for direct user interaction. Several additional functions, e.g. excess loop delay compensation, are made available to the designer. Further, the designed loop filter can be synthesized in CIFF and CIFB topology or CRFF and CRFB in the case of a bandpass modulator. Additionally, the toolbox offers the design of a closed loop Sigma-Delta sensor readout having the sensor as part of the loop filter. Furthermore, several typical non-idealities of CT Sigma-Delta modulators such as real opamp behavior, excess loop delay, and jitter, are simulated with a tremendously speed up via the application of the lifting approach.