Design Of High-performance Low-Power Consumption Sigma-Delta Analog To Digital Converter

The recent growth of portable consumer applications has increased the demand for low power audio analog converters. A key building block in audio systems is the analog to digital converter. Oversampling Sigma-Delta ADCs have the advantage of relaxed matching requirements on analog components. Furthermore, oversampling ADCs do not need step roll-off anti-alias filtering typically required in Nyquist-rate ADCs. Conceptually,Sigma-Delta ADCs provide high resolution and linearity, while using a low-resolution quantizer, by taking advantage of oversampling and noise shaping. Quantizer resolution, OSR,and loop filter order are three essential parameters to boost the Sigma-Delta modulator performance. Increasing any of these parameters creates trade-offs with several other design parameters, such as power dissipation, area, and complexity. The double-sampling and MASH can improve the performance of modulator without increasing power dissipation.This paper presents two high-precision low-power Sigma-Delta converters: CIFF structure with opamp-sharing and MASH structure. And the comparison in terms of power and precision will be made. The paper first introduces the development of Sigma-Delta ADC,and introduces the basic principles on the modulator. Then MASH and CIFF modulator non-ideal behavior modeling will be presented to get the circuit design specifications. The circuit blocks of the modulator, MASH and CIFF modulator are designed in the TSMC 0.35?m CMOS 2P4M process, 3.3V. The signal bandwidth is 2KHz, the sampling frequency is 11.264MHz, and the SNR of the MASH modulator is 109.4 of which power consumption is 38mW. The SNR of the CIFF with opamp-sharing is 95.0dB of which power consumption is 23.34mW. The modulators in this paper achieve comparable or better FOM in the recently published audio or low power modulator.The decimation filter is designed for the modulator output digital codes. The multistage digital is composed of CIC filter, CIC compensation filter and two halfband filters to down sample 256 OSR. The simulation results show the presented decimation filter has a ripple less than 0.03dB in the signal band, and Attenuation in stop band exceeds 120dB.