Analysis and Design of Reconfigurable Sense Amplifier for Compute SRAM With High-Speed Compute and Normal Read Access
Jian Chen, Wenfeng Zhao, Yuqi Wang, Yajun Ha
Abstract
A compute SRAM requires high speed for both compute access and normal read access. However, it presents a very distinct bitline discharging behavior in these two modes, thus brings a significant challenge to the design of its sensing amplifiers. State-of-the-art sensing amplifiers, namely the symmetric single-ended sensing amplifier (SS-SA) and the asymmetric differential sensing amplifier (AD-SA), cannot support a high-speed compute access and normal read access at the same time. To solve this problem, first, we perform a comprehensive analysis of these two sensing topologies and find that AD-SA requires a smaller bitline voltage difference than that of SS-SA, but it is still relatively large. This guides us to design an improved AD-SA for high-speed compute access. Second, we propose a novel reconfigurable sensing amplifier (R-SA) that can dynamically reconfigure its circuits in a compute access or in normal read access, to optimize its access delay in both modes. Compared to the state-of-the-art, results show that our R-SA has reduced the access delay by 17% and 45% for compute access and normal access, respectively, in an 8 Kb compute SRAM using a 55 nm CMOS technology. In addition, the proposed R-SA also saves the access energy by 9%.