Scavenging thermal-noise energy for implementing long-term self-powered CMOS timers

One of the major challenges in remotely powered sensors is that events being monitored can not be time-stamped due to the unavailability of a continuously active timer or system clock. Implementing such a timer would require access to a perennial source of energy, which for a structural health monitoring (SHM) application, could easily span several years. In this paper, we present a novel approach to implement self-powered timers that only requires presence of ambient thermal energy. The operational principle of the timer is based on the physics of trap-assisted electron transportation in floating-gate capacitors which yields leakage currents down to 10^-21A. Using a differential architecture the proposed timer compensates for the effects of temperature variations during the timer read-out. In this paper we validate the proof-of-concept using measurement results obtained from different timer topologies which have been prototyped in a 0.5μm CMOS process.