Compact self-powered CMOS strain-rate monitoring circuit for piezoelectric energy scavengers

Self-powered sensing refers to an energy scavenging approach where the power for sensing, computation and storage is harvested directly from the signal being sensed. Presented is a 16-transistor CMOS circuit that can be used for the self-powered sensing of strain-rates using signals produced by piezoelectric energy scavengers. By exploiting operational primitives inherent in impact-ionised hot-electron injection on a floating-gate transistor, the proposed circuit achieves computation and non-volatile storage of signal-rate statistics without the aid of batteries, intermediate energy storage, power regulation or analogue-to-digital conversion. By using a diode based analogue delay-line, the proposed circuit computes and stores the number of times the signal-rate (strain-rate) exceeds a threshold which can be programmed from 0.6 to 12 V/s. The circuit occupies 500 x 340 mu m of silicon when prototyped in a 0.5 mu m CMOS technology and measured results demonstrate power dissipation less than 200nW, which is ideal for self-powered sensing applications.