A self-terminated nonvolatile (NV) register that is a key component of digital LSI is proposed and its impact of minimizing write energy and leakage energy during backup operation before power off is presented. The self-terminated NV register can automatically cut off the write current pulse by continuously monitoring the volt-age change due to the state transition of the NV devices. Moreover, the write completion signal can be utilized for a flag whether the circuit goes into the idle state which results in the minimization of leakage energy consump-tion. A case study is performed using a 45nm CMOS technology and a spin-orbit torque device which result in 71% of total energy reduction in the backup operation compared to that of a typical worst-case design.