Senputing: An Ultra-Low-Power Always-On Vision Perception Chip Featuring the Deep Fusion of Sensing and Computing

Always-on intelligent visual perception applications are widely deployed in edges in the AIoT era. In order to eliminate power costs of data conversion and transmission, this paper proposes Senputing, an ultra-low-power processing-in-sensor chip that completely fuses sensing and computing together for a BNN-based hierarchical processing system. This chip could operate in two modes. In computation mode, photocurrents are directly utilized for computing without being converted into voltages, and the computation results of 1-st BNN layer are directly sent out to subsequent BNN processors for an always-on coarse classification, eliminating conversion power and storage cost of raw images. Once an interested objected is detected, this chip switches to sensor mode and sends raw images to potential full-precision processors or cloud servers for fine-grained recognition or segmentation. A $32\times 32$ prototype is fabricated with 180nm CMOS process. It accomplishes MNIST dataset classification task with the accuracy of 93.76% and the power consumption of 147nW at 156fps, achieving $13.1\times $ energy efficiency compared with state-of-the-art work.