Nonlinear Settling in Delta-Sigma Modulators

Abstract

High linearity in data converters is an important feature for various applications such as instrumentation and data acquisition. However, a good handle on nonlinear effects is impaired by the lack of analytical models. This situation is worsened by the fact that nonlinearities from different origins contribute to the overall nonlinearity of the converter and it is difficult, if not impossible, to identify them individually during chip testing. Many authors circumvent this problem by either treating the nonlinear effect as a small perturbation to the ideal modulator or even as an additive white noise source. These methods do not establish a clear relationship between circuit parameters and overall non-linearity. Therefore, they can not provide a quantitative guide for oversampled converters design.