一种可调精度的A/D转换器设计

Design of a Variable Resolution A/D Convertor

现代测控系统对测量信号的处理基本由数字技术完成,A/D转换器的性能对系统具有重要的影响.采用SDM(∑-?调制器)实现A/D转换器,省略复杂的数字抽取滤波器,由DSP和CPLD对SDM输出的高速码流处理,实现A/D转换.DSP软件编程可以控制CPLD的计数器,实现可变精度(和速度)的A/D转换.通过对SDM特性分析,得到转换方法及计算公式,最后设计电路实现要求的功能.实验实现了最高16位A/D转换,很好地证明了设计分析的结论.

Usually using digital technology to deal with the measure signal in a measurement and control system, and A/D convertor is one of key factor for the system performance. Design an A/D convertor by sigma delta modulator （SDM）, the complex digital decimation filter was omitted, and to processing the output 1 bit stream of SDM using DSP and CPLD to obtain the result. So software of DSP can control the counters of CPLD to obtain a variable resolution （and convertion speed） A/D convertor. By analysis the characters of SDM, the equations were obtained to finish A/D convertion, and design a practical circuit to implement the functions. Some experiments which achieved 16 bit A/D convertion proved the results effectively.