A 96-MB 3D-Stacked SRAM Using Inductive Coupling With 0.4-V Transmitter, Termination Scheme and 12:1 SerDes in 40-nm CMOS

A 28.8-GB/s 96-MB 3D-stacked SRAM is presented. A total of eight SRAM dies, designed in a 40-nm CMOS process, are vertically stacked and connected using an inductive coupling wireless link with a low-voltage NMOS push-pull transmitter that reduces the power of the link by 35% with a 0.4-V power supply. The SRAM utilizes an inverted bit insertion scheme that compensates for the degradation of the first transmitted bit, a coil termination scheme that aims to eliminate the ringing of 3D inductive coupling bus, and a 12:1 SerDes that minimizes power consumption and area overhead in inductive coupling channels. Low-power, large-capacity, 3-cycle latency 3D-stacked SRAM for a DNN accelerator is achieved with the combination of these techniques to serve as a replacement of 3D-stacked DRAM. The performance of the proposed 3D-SRAM is compared with HBM DRAM and achieves more than 50% lower energy consumption. The scaling scenario of the SRAM module is discussed in light of the scaling of the inductive coupling technology and logic process.