Low-power CMOS sensors are gaining increasingly more importance with the emergence of IoT. In this talk, circuit techniques for low-power fully integrated CMOS sensors will be presented. First, all-electrical sensors that are capable of monitoring non-electrical vital signs such as pulse wave velocity (PWV) and respiration will be described. Two key techniques are proposed to obtain wire-free and all-electrical measurement of PWV and respiration, which are bio-impedance (BI) and analog-modulated body-channel communication (BCC). Experimental result from prototype chip, which closely matches that of commercial non-electrical devices will be shown. Second, low-power voltage, current and time references will be discussed. By exploiting mobility and threshold variation of CMOS, voltage and current references are proposed, which have good temperature and supply stability. A low-power reference clock oscillator that can replace an external crystal will also be presented, which employs regulated oscillator in a temperature compensated feedback loop. Finally, techniques that allow CMOS to be used as sensing element will be shown. By exploiting the non-idealities of standard CMOS process such as changes in surface conductivity and dielectric constant, it will be shown that sensing humidity and pressure is possible in a standard CMOS process without any post-processing.
SeongHwan Cho received the B.S. degree in electrical engineering from KAIST, Korea, and the S.M. and Ph.D. degrees in EECS from MIT, Cambridge, MA. In 2002, he joined Engim, Inc., where he was involved in data converters and phased-locked loop (PLL) design. Since 2004, he has been with KAIST in the department of EE, where he is now a professor. His research interests include analog and mixed-signal circuits for low power communication systems, bio/health-care devices and CMOS sensors. Prof. Cho received the 2009 IEEE Circuits and System Society Guillemin-Cauer Best Paper Award and 2012 ISSCC Takuo Sugano Award for Outstanding Far-East Paper. Prof. Cho has served on the Technical Program Committee on several IEEE conferences, including ISSCC, Symp. on VLSI and A-SSCC. He serves as associate editor(AE) of JSSC and served as AE forTCAS-1. He also serves as a distinguished lecturer of IEEE Solid-State Circuits Society from 2015 to 2016.