Research And Design Of 16-bit Audio Sigma-Delta Analog-to-Digital Convertor

With the technology of over-sampling, noise-shaping and digital filtering, Sigma-Delta analog-to-digital converter can efficiently reduce the quantization noise from output signal band, thus improve the SNR (signal to noise ratio). Compared with traditional Nyquist converters, Sigma-Delta A/D converter reduce the requirements of performance specification and device accuracy to analog circuits, simplify the design, and reduce the cost of manufacture.Based on the principle research of the Sigma-Delta A/D converters, a 16 bits audio Sigma-Delta A/D converter was designed by using TSMC0.18um technology, 1.8V supply, 128 times over-sampling rate and 6.4MHz sampling frequency. In the modulator design, a multi-stage noise-shaping (MASH")2-1"cascade structure was adopted. At the same time, the effect of various non-ideal factors was taken into account. In the help of SDtoolbox, the modulator system was designed using SIMULINK. And block circuits including operational amplifier, comparator, bandgap voltage reference, CMOS switches, non-overlapping clock generation circuit, and so on were designed and simulated using Cadence Spectre. In the digital decimation filter design, the hierarchical decimation technology was adopted, and all level filters were designed by SPTool and FDATool in MATLAB software. Besides, in the basic of intrinsic algorithm of filter, the CIC filter and half-band filter were introduced. So, a three-stage decimation filter system was designed, which calculation and storage were relative less, thus the power consumption and chip area were great reduced.The simulation results showed that the SNR of this Sigma-Delta A/D converter reached 102.3dB, and met the system requirement of 16-bit resolution.