MCRA: Multicolumn Residue Accumulation Analog Compute-in-Memory Architecture With Time-Domain M-Input ΣΔ ADC

Analog compute-in-memory (ACIM) architectures offer significant throughput and energy benefits by performing multiplication-and-accumulation (MAC) operations directly within memory arrays. However, their overall efficiency is fundamentally constrained by the high power consumption of the per-column high-resolution analog-to-digital converters (ADCs) required to support modern DNNs (e.g., transformers), many of which demand both high computational precision and large-column throughput. In conventional ADC designs, energy in the noise-limited regime scales near-exponentially, typically by4×per additional bit, making high-resolution ADCs on every column power-prohibitive. This article proposes a high-precision and power-efficient multicolumn residue accumulation (MCRA) ACIM architecture to efficiently support precision-demanding modern DNNs. Each column uses a low-resolution coarse ADC (cADC), while the per-column residuals are accumulated and further quantized by an energy-efficient time-domain multi-input incremental sigma–delta (Mi-Σ Δ) fine ADC (fADC). This approach amortizes the near-exponential energy growth across columns, while exploiting the more favorable power-resolution scaling of the time-domain Mi-Σ Δquantization. Postlayout simulations demonstrate a 66.2-dB signal-to-noise-and-distortion ratio (SNDR) per column at only 1/21 the energy of the baseline with per-column high-resolution ADCs, and0.405×(1/2.47) the energy of an energy-saving ADC per column, which achieves a similar SNDR. Circuit- and system-level simulations demonstrate that our MCRA CIM architecture achieves negligible accuracy degradation in precision-demanding ViT tasks while delivering high energy and area efficiency.