A 44.3 TOPS/W SRAM Compute-in-Memory With Near-CIM Analog Memory and Activation for DAC/ADC-Less Operations

In this letter, we present an analog compute-in-memory (CIM) macro design which incorporates near-CIM analog memory and nonlinearity activation unit (NAU) to alleviate the DAC/ADC power bottleneck. Fully differential analog memory is designed with switched capacitor storage circuits. Activation function, e.g., rectified linear unit, is also performed in analog domain in NAU. The CIM macro is fabricated using TSMC 55-nm technology, with a peak macro-level efficiency of 44.3 TOPS/W and a system energy efficiency of 27.7 TOPS/W for analog input and output with 4-bit weight. The near-CIM analog memory and NAU solution brings 76.0% energy reduction compared with DAC/ADC solution, which contributes $1.34\times $ to $2.37\times $ energy efficiency improvement.