Simulation of sigma-delta data converters using SPICE

Research into sigma-delta based data converters at King´s College over the last three years, has focused firstly on the system level optimisation of loop-filter parameters and quantisation level for high-order modulators, and secondly on investigating the potential for adapting either of these to signal characteristics. A high-level representation can be employed directly in both A/D and D/A convertors, by substituting technology dependant equivalents for the integrators, summers, multipliers, and comparator. Examples are given for the integrator block in switched capacitor technology and as a fundamental digital element. Initial simulations were carried out using C-coded difference equation descriptions, and are hence primarily applicable to D/A conversion. More recently, consideration has been given to simulating an analogue implementation, suitable for A/D conversion. This paper presents the findings of this work, including results comparing analogue SPICE simulations to their digital equivalents