Biography
Enrollment Date: 2009
Graduation Date：2012
Degree：M.S.
Defense Date：2012.05.24
Advisors：Zhihua Wang Seng-Pan U
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Low Power Sigma-Delta Analog-to-Digital Converter for Biomedical Applications
Abstract:
Recently, with the development of economy and technology, people pay more and more attention to their health, so this provides a good opportunity to develop biomedical instruments. Analog-to-Digital Converter (ADC), which plays an important role in the electronic system in biomedical instruments, is a bridge to connect the analog world and digital world. It is a sensible choice to use ΣΔ modulator to design ADC for the 80dB resolution requirement. Nonetheless, as the process and power supply decline, it becomes more and more difficult to design low-power ΣΔ modulator. Therefore, low-power ΣΔ modulator research is significant to the biomedical instruments.
This thesis analyzes the main non-ideal factors which will affect the performance of ΣΔ modulator, and it gives the appropriate solutions to solve these problems. It proposes a new idea which brings noise-shaping to the Nyquist architecture in order to reduce the power consumption. Besides, after analyzing different architectures of ΣΔ modulator, it decides to use multi-bit quantizer single-loop architecture with feed-forward for the design. For the analog adder problem encountered in this architecture, it proposes two passive adder to solve this problem, which will reduce extra power consumption and meet the requirement of low-power design. In addition, this work uses a 4-bit SAR ADC as quantizer, which not only avoids the high frequency clock signal and complex logic circuits.
Finally, this work design a low-power ΣΔ modulator based on ST65nm 1P7M process. The real modulator’s resolution achieves 80dB and its FOM is 0.13pJ/step. Compared with the state-of-art modulators, this work achieves the frontier of this field.