Design of a Low-Energy MTJ-Based Nonvolatile Register Based on a Differential Information Storing Scheme

In intermittent computing enabling continuous information processing under unstable energy supply, it is important to minimize the energy consumption required to maintain intermediate information during frequent power supply interruptions. In this paper, we propose a new configuration of a magnetic-tunnel-junction (MTJ)-based nonvolatile register that can save intermediate information during intermittent operation in a short time with low energy consumption. The proposed nonvolatile register adopts a differential information storing scheme that expresses one-bit data by assigning ‘1’ when the states of two adjacent MTJ devices are the same and ‘0’ when they are different. This reduces the circuit area and energy consumption by reducing the number of MTJ devices in a register, as well as achieving quick backup and restoration by accessing MTJ devices in parallel. The evaluation using a 55 nm CMOS/MTJ-hybrid process technology shows that the proposed nonvolatile register can reduce the circuit area and energy consumption by 34% and 49%, respectively, compared to those of a conventional one.