Temperature sensors are routinely found in devices used to monitor the environment, the human body, industrial equipment, and beyond. In many such applications, the energy available from batteries or the power available from energy harvesters is extremely limited, thus the power consumption of sensing should be minimized in order to maximize operational lifetime.
Researchers at UC San Diego have developed a sensor that can monitor its environment with near zero power, enabling ultra-long battery life, or energy harvesting from low-power sources towards energy-autonomous operation. Specifically, two pA current references are generated via small tunneling-current metal-oxide-semiconductor field effect transistors (MOSFETs) that are independent and proportional to temperature, respectively, which are then used to charge digitally-controllable banks of metal-insulator-metal (MIM) capacitors that, via a discrete-time feedback loop that equalizes charging time, digitize temperature directly. The proposed temperature sensor was integrated into a silicon microchip and occupied 0.15 mm2 of area. Four tested microchips were measured to consume only 113 pW with a resolution of 0.21oC and an inaccuracy of ±1.65oC, which represents a 628x reduction in power compared to prior-art without a significant reduction in performance.
This invention is a useful as a sensor for applications with sub-nW power consumption requirements. Some examples include usage in:
A prototype model was constructed utilizing a microchip fabricated in a 65 mm 1P9M commercial technology. More die-to-die, wafer-to-wafer, and lot-to-lot measurements would be needed in future work to validate accuracy for volume manufacturing.
A provisional patent has been submitted and the technology is available for licensing.
sensor, sub-nW power consumption, “Internet of Things”, wearable & biomedical devices