A Column-Parallel Time-Interleaved SAR/SS ADC for Computing in Memory with 2-8bit Reconfigurable Resolution

Abstract

Computing in Memory (CiM), as a computing system with non-von Neumann architecture, has been reported as one of the most promising neural network accelerators in the future. Compared with digital-based computation, CiM uses RAM arrays to calculate and store in the analog domain, avoiding the high delay and energy consumption caused by data transfer. However, the computational results require data converters for quantization, which often limits the development of high-performance CiMs. In this work, we propose a 2-8bit reconfigurable time-interleaved hybrid ADC architecture for high-speed CiMs, including successive approximation and single-slope stages. Reconfigurability introduces a trade-off between resolution and conversion speed for ADCs in different computing scenarios. A prototype was implemented in a 55 nm CMOS technology, which occupies an area of 330μm × 13μm and consumes a power of 1.429mW at 8-bit conversion mode. With a Nyquist frequency input sampled at 350 MS/s, the SNDR and SFDR are 40.93 dB and 51.08 dB, respectively. The resultant Walden figure of merit is 44.8 fJ/conv.