Sigma-delta DAC Design

Compared with the traditional DAC, Sigma-delta DAC technology have the advantages that the analog circuit chip area is small, less demanding on the device matching and technology is easy to achieved.At the same time, stricting quantization noise and stability in differential treatment can be obtained under the same cost of traditional rate of DAC were difficult to reach. Sigma-delta DAC as a high-precision signal converter, in today's digital audio, communications and other fields is widely used. Based on the purpose of controlling fine-tuning capacitor of voltage-controlled crystal oscillator, it is this research topic to design a DAC chip.This article describes the principles of digital-analog converter, index of DAC and related meanings of individual,over-sample sigma-delta DAC technical principles and structure, sigma-delta modulator structure and principle; talking about the first order, second order, higher order modulation, multi- bit modulator characteristics, signal to noise ratio, distribution of poles and zeros, stability, transmission characteristics, linearity and other characteristics; illustrates the detailed design of the modulator technology, including the Verilog code to describe the related work, simulation, optimization of alignment parameters , synthesis, timing analysis, design- ing a 5th-order single-bit modulator; completing a digital-analog conversion (1bit DAC) and the switched capacitor filter designing.Completing analog sub-modules circuit, including switched-capacitor circuit, the clock does not overlap circuit, operational amplifier design; using CANDANCE SPECTRE software to simulate circuit design. Simulation results show that the design of the Sigma-delta modulator can get signal to noise ratio of 93, more than 14 significant digits, normalized to the maximum stable input of 0.56 meeting the design requirements.