LOKI: a 0.266 pJ/SOP Digital SNN Accelerator with Multi-Cycle Clock-Gated SRAM in 22nm

Abstract: Bio-inspired sensors like Dynamic Vision Sensors (DVS) and silicon cochleas are often combined with Spiking Neural Networks (SNNs), enabling efficient, event-driven processing similar to biological sensory systems. To realize the low-power constraints of the edge, the SNN should run on a hardware architecture that can exploit the sparse nature of the spikes. In this paper, we introduce LOKI, a digital architecture for Fully-Connected (FC) SNNs. By using Multi-Cycle Clock-Gated (MCCG) SRAMs, LOKI can operate at 0.59 V, while running at a clock frequency of 667 MHz. At full throughput, LOKI only consumes 0.266 pJ/SOP. We evaluate LOKI on both the Neuromorphic MNIST (N-MNIST) and the Keyword Spotting k(KWS) tasks, achieving 98.0 % accuracy at 119.8 nJ/inference and 93.0 % accuracy at 546.5 nJ/inference respectively.