Sensors with long lifetimes are ideal for infrastructure monitoring. Miniaturized sensor systems are only capable of storing small amounts of energy. Prior work has increased sensor lifetime through the reduction of supply voltage , necessitating voltage conversion from storage elements such as batteries. Sensor lifetime can be further extended by harvesting from solar, vibrational, or thermal energy. Since harvested energy is sporadic, it must be detected and stored. Harvesting sources do not provide voltage levels suitable for secondary power sources, necessitating DC-DC upconversion. We demonstrate a 8.75mm³ sensor system with a near-threshold ARM microcontroller, custom 3.3fW/bit SRAM, two 1mm² solar cells, a thin-film Li-ion battery, and integrated power management unit. The 7.7μW system enters a 550pW data-retentive sleep state between measurements and harvests solar energy to enable energy autonomy. Our receiver and transmitter architectures benefit from a design strategy that employs mixed signal and digital circuit schemes that perform well in advanced CMOS integrated circuit technologies. A prototype transmitter implemented in 0.13μm CMOS satisfies the requirements for Zigbee, but consumes far less power consumption than state-of-the-art commercial devices.

Date Published: 4 April 2012
PDF: 10 pages
Proc. SPIE 8347, Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2012, 83470U (4 April 2012); doi: 10.1117/12.916301

Published in SPIE Proceedings Vol. 8347:
Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2012
Andrew L. Gyekenyesi, Editor(s)