A 40nm Analog-Input ADC-Free Compute-in-Memory RRAM Macro with Pulse-Width Modulation between Sub-arrays

This paper presents an ADC-free compute-in-memory (CIM) RRAM-based macro, exploiting the fully analog intra-/inter-array computation. The main contributions include: 1) a lightweight input-encoding scheme based on pulse-width modulation (PWM), which improves the compute throughput by ~7 times; 2) a fully analog data processing manner between sub-arrays without explicit ADCs, which does not introduce quantization loss and saves the power by a factor of 11.6. The 40nm prototype chip with TSMC RRAM achieves energy efficiency of 421.53 TOPS/W and compute efficiency of 360 GOPS/mm² (normalized to binary operation) at 100MHz.