LAXOR: A Bit-Accurate BNN Accelerator with Latch-XOR Logic for Local Computing

Binary Neural Network (BNN) accelerators are attractive solutions for Artificial Internet-of-Things (AIoT) applications thanks to the compact models and low computational cost while maintaining satisfactory classification performance. Various analog/mix-signal compute-in-memory macros have been proposed to boost the energy efficiency of binary convolution tasks. However, this approach incurs inaccurate computation due to its sensitivity to temperature, noise, and process variations. In this work, we present a full-digital BNN architecture that leverages a novel Latch-XOR logic array for local bitwise multiplication, suppressing massive data movement and achieving 4.2× lower energy per operation compared to the decoupled standard cell approach. An optimized population count circuitry is also proposed for data accumulation, which obtains 1.37× Energy-Delay-Area saving compared to Binary-Adder-Tree-based implementation. To enable seamless hardware-software co-optimization, we have developed an in-house simulator for design space exploration as well as flexible mapping with various network topologies and kernel sizes. Our experiment shows the Latch-XOR-based architecture in 28nm CMOS technology achieves an enhanced energy efficiency of 2315 TOPS/W, 3.4× higher compared to the state-of-the-art synthesized digital architecture. This manifests that the proposed accelerator is highly suited for AIoT applications.