Nonvolatile Radiation Hardened DICE Latch

Spintronic-based integrated circuits have been widely considered as potential candidates for space application, due to the fact that their core devices (e.g. magnetic tunnel junction, MTJ) are intrinsic insensitive to radiation effects. However, their CMOS peripheral circuits are still vulnerable to radiation effects. In order to solve this problem, radiation hardening techniques (by process or by design) arc supposed to be developed. Hardening by process turns to be impractical, as it is relatively expensive and inefficient, whereas solutions by design at circuit level are currently preferred. Specifically, the dual interlocked storage cell (DICE) has been proposed for radiation hardening design. The DICE is relatively robust against single event upset (SEU), but it is power-inefficiency as it uses a dual structure to store only one bit of data. In addition, the DICE should be always power-on to retain data, consuming much static power. In this paper, we propose a nonvolatile DICE latch (NV-DICE), by integrating two magnetic tunnel junctions (MTJs) into the cell, which exhibits great potential for protecting against SEU with nonvolatility for low power consumption. By utilizing STMicroelectronics 40 nm design kit and a compact MTJ model, hybrid simulations are performed to demonstrate the functionality and performance of the proposed NV-DICE.