Design of a spatiotemporal correlation filter for event-based sensors

This paper reports the design of a 1mW, 10ns-latency mixed signal system in 0.18μm CMOS which enables filtering out uncorrelated background activity in event-based neuromorphic sensors. Background activity (BA) in the output of dynamic vision sensors is caused by thermal noise and junction leakage current acting on switches connected to floating nodes in the pixels. The reported chip generates a pass flag for spatiotemporally correlated events for post-processing to reduce communication/computation load and improve information rate. A chip with 128×128 array with 20×20μm² cells has been designed. Each filter cell combines programmable spatial subsampling with a temporal window based on current integration. Power-gating is used to minimize the power consumption by only activating the threshold detection and communication circuits in the cell receiving an input event. This correlation filter chip targets embedded neuromorphic visual and auditory systems, where low average power consumption and low latency are critical.