An 8-bit Ring-Amplifier Based Mixed-Signal MAC Circuit With Full Digital Interface and Variable Accumulation Length

An 8-bit switched-capacitor multiply-and-accumulator (MAC) in 65nm CMOS is presented. Based on a cascaded low-power ring-amplifier-based switched-capacitor DACs, the MAC circuit features a programmable accumulation length in MAC computation. Fabricated in 65nm CMOS, the prototype MAC circuit achieves a precision-scaled energy efficiency of 1.32fJ per MAC operation, which is comparable to other state-of-the-art MAC circuits, along with best-in-class linearity. The noise performance has been verified using four real-world convolutional neural networks (CNNs) and 10,000-image data sets with up to 1,000 classes with an accuracy drop of less than 2% compared to the baseline 32-bit floating-point MAC.