Spin-torque sensors for energy efficient high-speed long interconnects

In this paper, we propose a spin-torque (ST)-based sensing scheme that can enable energy efficient multibit long distance interconnect architectures. Current-mode interconnects have recently been proposed to overcome the performance degradations associated with conventional voltage-mode copper interconnects. However, the performance of current-mode interconnects are limited by analog current sensing transceivers and equalization circuits. As a solution, we propose the use of ST-based receivers that use magnetic tunnel junctions and simple digital components for current-to-voltage conversion, and do not require analog transceivers. We incorporate spin-Hall metal in our design to achieve high-speed sensing. We show both single and multibit operations that reveal major benefits at higher speeds. Our simulation results show that the proposed technique consumes only 3.93-4.72 fJ/b/mm energy while operating at 1-2 Gb/s, which is considerably better than existing chargebased interconnects. In addition, voltage-controlled magnetic anisotropy (VCMA) can reduce the required current at the sensor. With the inclusion of VCMA, the energy consumption can be further reduced to 2.02-4.02 fJ/b/mm.