Energy-Efficient and Robust Associative Computing with Injection-Locked Dual-Pillar Spin-Torque Oscillators

In this paper, we show that the dynamics of injection-locked spin-torque oscillators (STOs) can be exploited for non-Boolean information processing, such as associative computing. Injection locking employs phase synchronization of multiple STOs to a common injected ac current. DC inputs derived from external stimuli can be used to conditionally unlock some of the STOs. This phenomenon can be used for pattern identification. In such a scheme, stronger ac current injection can provide variation- and noise-tolerant global synchronization required for robust computation. We analyze dual-pillar STO (DP-STO) for low-power computing using injection locking method. A DP-STO offers a low-resistance bias terminal for ultralow-voltage ac injection, leading to low biasing power. Simultaneously, it provides a separate high-resistance sensing terminal with a large output swing, leading to compact and low-power sensing interface. Thus, an array of injection-locked DP-STOs can be suitable for energy-efficient and robust non-Boolean computing.