Clock Feedthrough in CMOS Analog Transmission Gate Switches

An analysis of clock feedthrough in CMOS analog transmission gate (TG) switches is presented in this paper. The mechanism for clock feedthrough and a related model of a transmission gate switch are established in the current-voltage domain. A region map is developed for the TG switch during the period when both devices are turned off. The region map is further divided into zones. From these region and zone maps, the sign and relative magnitude of the clock feedthrough noise can be efficiently estimated for different signal levels. Placing the input voltage near half of the power supply voltage is a useful technique for minimizing clock feedthrough noise. A model of clock feedthrough noise as compared with SPICE simulations exhibits less than 3% error. This research was supported in part by the Semiconductor Research Corporation under Contract No. 99-TJ-687, the DARPA/ITO under AFRL Contract F29601-00-K-0182, grants from the New York State Office of Science, Technology & Academic Research to the Center for Advanced Technology—Electronic Imaging Systems and to the Microelectronics Design Center, and by grants from Xerox Corporation, IBM Corporation, Intel Corporation, Lucent Technologies Corporation, and Eastman Kodak Company. Weize Xu received the B.S. degree from Nanjing University of Posts and Telecommunications, China in 1982, and the M.S. degrees from the University of Rhode Island in 1993, both in electrical engineering. Since 1997, he has been a senor research engineer and analog IC design specialist at Eastman Kodak Company. His research interests include high speed analog IC designs, pipelined A/D converter, low power switched capacitor circuit analysis and design, CMOS image sensor design, and analysis of noise in mixed signal ICs. He currently is a Ph.D candidate at the University of Rochester. Eby G. Friedman (S'78-M'79-SM'90-F'00) received the B.S. degree from Lafayette College in 1979, and the M.S. and Ph.D. degrees from the University of California, Irvine, in 1981 and 1989, respectively, all in electrical engineering. From 1979 to 1991, he was with Hughes Aircraft Company, rising to the position of manager of the Signal Processing Design and Test Department, responsible for the design and test of high performance digital and analog IC's. He has been with the Department of Electrical and Computer Engineering at the University of Rochester since 1991, where he is a Distinguished Professor, the Director of the High Performance VLSI/IC Design and Analysis Laboratory, and the Director of the Center for Electronic Imaging Systems. He also enjoyed a sabbatical at the Technion—Israel Institute of Technology during the 2000/2001 academic year. His current research and teaching interests are in high performance synchronous digital and mixed-signal microelectronic design and analysis with application to high speed portable processors and low power wireless communications. He is the author of more than 250 papers and book chapters, several patents, and the author or editor of seven books in the fields of high speed and low power CMOS design techniques, high speed interconnect, and the theory and application of synchronous clock distribution networks. Dr. Friedman is the Regional Editor of the Journal of Circuits, Systems, and Computers, a Member of the editorial boards of the Proceedings of the IEEE, Analog Integrated Circuits and Signal Processing microelectronics Journal, and Journal of VLSI Signal Processing, a Member of the Circuits and Systems (CAS) Society Board of Governors, and a Member of the technical program committee of a number of conferences. He previously was the past Editor-in-Chief of the IEEE Transactions on VLSI Systems, a Member of the editorial board of the IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing, Chair of the IEEE Transactions on VLSI Systems steering committee, CAS liaison to the Solid-State Circuits Society, Chair of the VLSI Systems and Applications CAS Technical Committee, Chair of the Electron Devices Chapter of the IEEE Rochester Section, Program or Technical chair of several IEEE conferences, Guest Editor of several special issues in a variety of journals, and a recipient of the Howard Hughes Masters and Doctoral Fellowships, an IBM University Research Award, an Outstanding IEEE Chapter Chairman Award, and a University of Rochester College of Engineering Teaching Excellence Award. Dr. Friedman is a Senior Fulbright Fellow and an IEEE Fellow.