Design of 8-Bit SAR ADC for Biomedical Applications

Abstract

Design of 8-Bit SAR ADC for Biomedical Applications Ankathi Gangaraju Department of Electronics and Communication Engineering National Institute of Technology Rourkela Design of 8-Bit SAR ADC for Biomedical Applications Thesis submitted in partial fulfillment of the requirements of the degree of Master of Technology in VLSI Design and Embedded systems by Ankathi Gangaraju (Roll Number: 215EC2098) based on research carried out under the supervision of Prof. Sougata Kumar Kar April, 2017 Department of Electronics and Communication Engineering National Institute of Technology Rourkela ii Department of Electronics and Communication Engineering National Institute of Technology Rourkela May 26, 2017 Certificate of Examination Roll Number: 215EC2098 Name: Ankathi Gangaraju Title of Dissertation: Design of 8-bit SAR ADC for Biomedical Applications. We the below signed, after checking the thesis mentioned above and the official record book (s) of the student, hereby state our approval of the thesis submitted in partial fulfillment of the requirements of the degree of Master of Technology in Electronics and Communication Engineering at National Institute of Technology Rourkela. We are satisfied with the volume, quality, correctness, and originality of the work. Prof. Sougata Kumar Kar Principal Supervisor iii Department of Electronics and Communication Engineering National Institute of Technology Rourkela May26, 2017 Prof. Sougata Kumar Kar Assistant Professor Supervisors’ Certificate This is to certify that the work presented in the thesis entitled. Design of 8-bit SAR ADC for Biomedical Applications submitted by Ankathi Gangaraju, Roll Number 215EC2098, is a record of original research carried out by him under our supervision and guidance in partial fulfillment of the requirements of the degree of master of Technology in Electronics and Communication Engineering. Neither this dissertation nor any part of it has been submitted earlier for any degree or diploma to any institute or university in India or abroad. Prof. Prof. Sougata Kumar Kar Principal Supervisor iv Dedicated to My beloved Brother Mahesh Varma and Sister Mounika And all my dear friends without whom none of my success would be possible. Signature v Declaration of Originality I, Ankathi Gangaraju, Roll Number 215EC2098 hereby declare that this thesis entitled Design of 8-bit SAR ADC for Biomedical Applications, presents my original work carried out as a master student of NIT Rourkela and, to the best of my knowledge, contains no material previously published or written by another person, nor any material presented by me for the award of any degree or diploma of NIT Rourkela or any other institution. Any contribution made to this research by others, with whom I have worked at NIT Rourkela or elsewhere, is explicitly acknowledged in the thesis. Works of other authors cited in this dissertation have been duly acknowledged under the sections “Reference” or “Bibliography”. I have also submitted my original research records to the scrutiny committee for evaluation of my dissertation. I am fully aware that in case of any non-compliance detected in future, the Senate of NIT Rourkela may withdraw the degree awarded to me on the basis of the present thesis. May 26, 2017 Ankathi Gangaraju NIT Rourkela vi Acknowledgment These two years of student life at NIT Rourkela have been filled with wonderful experiences, a lot of hard-works, tremendous joys and precious friends. This research work is one of the important accomplishments in my life and is completed because of the continuous support, encouragement and motivation given by so many in every part of my life. It is an immense delight to have this opportunity to express my gratitude and respect to them. First and foremost, I would like to thank my project supervisor Prof. Sougata Kumar Kar for the opportunities he gave to me, for his invaluable advices and for believing my abilities throughout the period. . Without his thoughtful encouragement and supervision, this thesis would never have taken shape. I gratefully acknowledge the support and guidance of all faculty members of Electronics and Communication Department and dept. staffs in Lab who have contributed their precious time to help me in completing my project. I am also grateful to Head of the Electronics and Communication Engineering Department Prof. Kamalkant Mahapatra for providing necessary facilities in the department. I am also grateful to Mr. Rakesh, Mr. Soubhagya, Mr. Apoorva, Ph.D. Scholar of VLSI Design and Embedded Systems and Siva Krishna Reddy, Suresh Manchala, Ashutosh Kumar Singh, G Vinod Kumar, Manne Subrahmanyeswara Rao, Bilahari Guruputi, Sruthi Peerila, Akshdeepika Sharma, and Ganta Yamini, M.Tech Scholars of VLSI Design and Embedded Systems, Electronics & Communication Engineering, National Institute of Technology, Rourkela, who worked with me in every difficulty faced during my project work. May 26, 2017 Ankathi Gangaraju NIT Rourkela Roll no- 215EC2098 vii ABSTRACT There has been a growing need for Successive Approximation ADC in recent years. Biomedical applications demand for long battery life-time which needs the requirement for designing ultra-low powered SAR ADCs. SAR analog to digital converter architecture is chosen in this master thesis project because it is one of the successful ADC which requires moderate resolution among all data converter with low power consumption. This thesis work investigates and compares different structures of comparator and SAR control logics. Based on the analysis double tail dynamic comparator is suited for the project and SAR control logic type 2 is considered for designing the SAR control logic block because of its minimal power consumption compared to the SAR control logic type1. Digital to Analog converter is designed with the split capacitive based DAC structure. The 8-bit SAR ADC design is done in cadence virtuoso 180 nm technology with 1.5 V power supply and power consumption of the ADC is found to be 25 µW for 1.5 V supply. Layout of double tail dynamic comparator and SAR control logic is done in SCL 180 nm technology. LVS is verified for the two mentioned layouts.