A 28nm 1.80Mb/mm2 Digital/Analog Hybrid SRAM-CIM Macro Using 2D-Weighted Capacitor Array for Complex Number Mac Operations
🤖 AI Summary
To address the low computational density, high error rates, and large latency of SRAM-based compute-in-memory (CIM) macros in complex multiply-accumulate (MAC) operations under the 28 nm process, this work proposes a hybrid digital/analog CIM architecture. It synergistically combines high-bit digital CIM with low-bit analog CIM and employs a two-dimensional weighted capacitor array to directly output complex real and imaginary components within a single cycle—eliminating the need for input digital-to-analog converters (DACs). This design circumvents the precision limitations of conventional analog CIM and the area overhead of fully digital CIM. Implemented in a 28 nm 6T-SRAM technology, the macro achieves an ultra-high memory density of 1.80 Mb/mm² and a low root-mean-square error of 0.435%. The architecture significantly improves energy efficiency and computational throughput for complex arithmetic, establishing a high-density, high-accuracy CIM hardware foundation for spectrally efficient wireless communications and AI acceleration.
Application Category
📝 Abstract
A 28nm dense 6T-SRAM Digital(D)/Analog(A) Hybrid compute-in-memory (CIM) macro supporting complex num-ber MAC operation is presented. By introducing a 2D-weighted Capacitor Array, a hybrid configuration is adopted where digital CIM is applied only to the upper bits and ana-log CIM is applied to the rest, without the need for input DACs resulting in improved accuracy and lower area overhead. The CIM prototype macro achieves 1.80 Mb/mm2 memory density and 0.435% RMS error. Complex CIM unit outputs real and imaginary part with a single conversion to reduce latency.
Problem
Research questions and friction points this paper is trying to address.
Enabling complex number MAC operations in SRAM
Reducing area overhead without input DACs
Improving computational accuracy with hybrid digital/analog design
Innovation
Methods, ideas, or system contributions that make the work stand out.
Hybrid digital/analog CIM architecture
2D-weighted capacitor array technique
Single conversion complex number processing
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