DIGITAL-TO-ANALOG CONVERSION USING DELTA-SIGMA MODULATORS IMPLEMENTED IN VIRTEX-4 FPGA DEVICES

摘要

This paper presents some selected architectures of delta-sigma modulators which are suitable for implementation of digital-to-analog converters (DACs) in modern FPGA devices. Simulation and implementation of simple architectures of first and second order of digital-to-analog converters in FPGA chip is described. Experimental tests have been performed using the evaluation board ML401 from Xilinx, based on the XC4VLX25 Virtex-4 chip. The quality of DACs has been measured and described by relevant power spectrum diagrams and differential linearity functions. Detailed comparison of DAC architectures is also given in terms of used resources and maximum operating frequency. It has been shown that carefully designed delta-sigma modulators implemented using modern FPGA technology are competitive to conventional integrated DACs. Consequently, multichannel DACs and ADCs of good quality can be designed within the FPGA chip. In this way, the idea of single-chip measurement system containing all essential parts as DACs, ADCs, CPU and digital I/O becomes an interesting alternative to the classical approach based on the multi-chip and/or ASIC technology.