Behavioral simulation of analog to digital converters

Abstract

The design of high-speed and high-resolution data converters is very difficult due to complexity of architectures used for converting analog signals into their digital representation. Since the introduction of the simplest conversion technique called parallel or flash technique numerous other architectures have been developed, for example n-stage pipeline, reference feed-forward architecture, folding and interpolating technique. The variety of A/D converter architectures additionally complicates design process due to fact that there is no available behavioral simulator, which can be utilized to support verification of particular converter's design. Many effects and imperfections present in A/D converters influence their performance, for example: switching imperfections, finite gain, clock jitter, and switching and coupling (Electro-Magnetic and substrate perturbations). In most cases several simulation tools have to be used to very performance of designed A/D converter. In this work a new methodology for behavioral simulation of A/D converters has been presented. Novel approach in behavioral modeling of A/D converters is based on utilization of Dynamic Linked Libraries (DLLs) to encapsulate behavior of basic modules of A/D converters. Predefined Basic Building Modules (BBMs) of A/D converters such as comparators, folding circuits, analog switches, binary encoders and many others are used to form a behavioral model of various types of A/D converters. Imperfections of BBMs are separated from the simulator framework and included into behavioral description of BBMs kept in DLL modules. Utilization of DLL modules gives a very convenient way for modifying BBMs independently from the simulator framework, and because DLL modules are executable files simulation time is significantly reduced (no translation or interpretation of simulation language commands is needed). Developed Behavioral Simulator of A/D converters is implemented in Visual C++ language and is partially based on an event driven simulation scheme and a data flow technique. The data flow technique was introduced into the simulator architecture to reduce number of events generated during simulation process, which additionally reduces simulation time. Several BBMs have been defined and constructed as DLL modules to support simulation of various types of A/D converters including flash, multi-stage, pipelined, and folding A/D converters.