A Novel Asynchronous Pixel for an Energy Harvesting CMOS Image Sensor

This paper proposes a novel energy harvesting technique based on an asynchronous pixel structure and an efficient energy generation scheme, referred to as avalanche energy generation (AEG). The key idea behind using an asynchronous type of pixel is to lower the power consumption by enabling only active pixels to be read-out after which they enter into a power generation mode. In this mode, the on-pixel photodetector itself will be used to harvest the light energy from the environment and make it available to active pixels. A very interesting feature about our proposed approach is that during a frame capture, critical energy is mainly required for starting-up activity. Once a group of pixels have been read-out, the available energy will rise and more array activity will contribute to the generation of more energy, hence creating an avalanche effect. In contrast to other early designs of energy harvesting image sensors, our scheme uses the photodetector itself for power generation. This results in better utilization of the photosensitive area and more importantly an improved energy generation scheme. Detailed power analysis and extensive simulation results are provided in this paper, which validate the proposed concept. Three test structures have been fabricated in AMIS 1-poly, 5-metal CMOS 0.35-m n-well process. The power generation process and event generation have been successfully verified experimentally.