Skyrmion Sensor-Based Low-Power Global Interconnects

In this paper, we propose the use of magnetic skyrmion sensors for low-voltage, low-current global interconnects. Magnetic skyrmions have shown great potential for low-power circuit applications, since skyrmions can be generated and moved by remarkably low-current pulses. We propose the use of skyrmion-based current sensors at the receiver that allows low-current signal transmission through the line. The proposed skyrmion sensor consists of a magnetic nanotrack on top of a spin-Hall metal (SHM). The skyrmion is nucleated in the nanotrack by using spin-polarized current and, subsequently, moved along the nanotrack by using a charge current through the SHM. This charge current is the input current from a global interconnect line, which moves the skyrmion depending on the logic input to the line. The resistance of a magnetic tunnel junction (MTJ) at the receiver is based on the movement/location of the skyrmion. This resistance change is sensed using a reference MTJ and a simple complementary metal-oxide-semiconductor (CMOS) inverter. Such a receiver configuration acts as a built-in latch, and hence, expensive voltage converters or transimpedance amplifiers can be avoided, which are the bottlenecks in a conventional low-power interconnect design. Our simulation results indicate that for a 10 mm Cu-line in 45 nm CMOS technology, the energy consumption with skyrmion-based sensing is similar to 50x lower compared with full swing and similar to 25x lower compared with low-swing CMOS interconnect.