SOT-MRAM-Based Approximate Content Addressable Memory for DNA Classification

In this work, we propose an approximate content addressable memory (CAM) using a hybrid CMOS-spin-transfer torque (STT)-spin-orbit–torque MRAM (SOT MRAM) cell for deoxyribonucleic acid (DNA) classification. Our proposed 5T-1R approximate nonvolatile CAM (ANV-CAM) cell provides large hamming distance (HD)/mismatch tolerance (>64 bits) for a 256-bit CAM word size while achieving a small area overhead compared with the existing works. We analyze the performance of our ANV-CAM cell using a calibrated Verilog-A-based STT-SOT MRAM device model. We perform 1000 point Monte Carlo (MC) simulations including local CMOS transistor and SOT magnetic tunnel junction (SOT-MTJ) device variations at different process corners to assess the HD tolerance of our proposed cell. Our proposed CAM cell design is area-efficient and enables faster, energy-efficient approximate search operation with a search delay of ~0.6 ns and a search energy/bit of ~4 fJ.