A 1-V Wide Swing Image Sensor With Simultaneous Energy Harvesting and Imaging Modes for IoT Applications

Image sensors with energy-harvesting capabilities aid in the development of self-powered Internet of Things (IoT) nodes. By achieving simultaneous energy harvesting and imaging, these image sensors make it possible to eliminate batteries and directly achieve self-powered operation. The article proposes a 1-V wide swing image sensor with simultaneous energy harvesting and imaging modes. The proposed pixel utilizes a vertical n+/p-well/DNW/P-sub structures as the photodiode based on a standard 180-nm CMOS mixed-signal process. The n+/p-well is used for imaging, while the p-well/DNW and DNW/P-sub are used for energy harvesting with p-well and P-sub shorted together. Moreover, a traditional 4T pixel has been improved by using CMOS pairs as the switches and zero-threshold NMOS as the source follower. The rail-to-rail pixel output swing can be achieved. An image sensor with simultaneous energy harvesting and imaging modes, which consists of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$32\times 32$ </tex-math></inline-formula> pixel array, a controller, and a dual-channel PWM quantizer, has been designed and fabricated. Measurement results show that the average power consumption of the image sensor is approximately 899.6 nW with 25 fps at 3 klx. The proposed image sensor has a DR of 47.3 dB under a 1-V supply. The measured power generated by energy harvesting while maintaining imaging functionality is 194 pW/lx/mm2.