Energy-Efficient and Robust Associative Computing with Electrically Coupled Dual Pillar Spin-Torque Oscillators

TL;DR

This paper compares magnetic and electrical coupling in spin-torque oscillators, demonstrating electrical coupling's superior robustness and proposing a dual-pillar design for low-power, noise-resilient associative computing.

Contribution

It introduces a dual-pillar STO design and analyzes electrical coupling's advantages over magnetic coupling for scalable, energy-efficient, and robust oscillator-based computing.

Findings

Electrical coupling maintains phase-locking with larger parameter variations.

Magnetic coupling fails beyond ~3% variation, even in small clusters.

Dual-Pillar STO enhances exploitation of electrical coupling for low-power applications.

Abstract

Dynamics of coupled spin-torque oscillators can be exploited for non-Boolean information processing. However, the feasibility of coupling large number of STOs with energy-efficiency and sufficient robustness towards parameter-variation and thermal-noise, may be critical for such computing applications. In this work, the impacts of parameter-variation and thermal-noise on two different coupling mechanisms for STOs, namely, magnetic-coupling and electrical-coupling are analyzed. Magnetic coupling is simulated using dipolar-field interactions. For electricalcoupling we employed global RF-injection. In this method, multiple STOs are phase-locked to a common RF-signal that is injected into the STOs along with the DC bias. Results for variation and noise analysis indicate that electrical-coupling can be significantly more robust as compared to magnetic-coupling. For room-temperature simulations, appreciable phase-lock was retained among tens of electrically coupled STOs for up to 20% 3s random variations in critical device parameters. The magnetic-coupling technique however failed to retain locking beyond ~3% 3s parameter-variations, even for small-size STO clusters with near-neighborhood connectivity. We propose and analyze Dual-Pillar STO (DP-STO) for low-power computing using the proposed electrical coupling method. We observed that DP-STO can better exploit the electrical-coupling technique due to separation between the biasing RF signal and its own RF output.