A 28-nm Cascode Current Mirror-Based Inconsistency-Free Charging-and-Discharging SRAM-CIM Macro for High-Efficient Convolutional Neural Networks

Computing-in-memory (CIM) is an emerging approach to alleviate the von Neumann bottleneck and enhance energy efficiency and throughput. This brief introduces a 16-Kb static random access memory (SRAM) CIM macro for convolutional neural networks (CNNs), featuring a cascode current mirror-based inconsistency-free computing circuits (CICCs). The bias voltage of CICC is provided by a cascode current mirror (CCM) circuit. The proposed architecture improves the consistency and linearity of bitline (BL) charge and discharge rates in the analog current domain, enhancing computational accuracy. Additionally, the charge and discharge on the BLs represent the positive or negative calculation result, eliminating the need for extra encoding and logic circuits to handle sign bits. The SRAM-CIM macro achieves an energy efficiency of 59.1–134.0 TOPS/W and a throughput of 0.41 TOPS in a 28-nm CMOS technology, and the estimated inference accuracy on MNIST and CIFAR-10 datasets is 96.5% and 91.4%, respectively, with 5-bit input precision and 1-bit weight precision.