A power-gated MPU with 3-microsecond entry/exit delay using MTJ-based nonvolatile flip-flop

We propose a novel power-gated microprocessor unit (MPU) using a nonvolatile flip-flop (NV-F/F) with magnetic tunnel junction (MTJ). By using the NV-F/F to store the MPU's internal state, this MPU realizes power-gating operation with a small 3-microsecond entry/exit delay penalty in power-on/power-off, which is one order of magnitude faster than a conventional MPU's deep power down mode. To achieve this short entry/exit delay, an appropriate NV-F/F circuit, which can perform stable high speed store/recall operations, has been developed. The MPU will help in the realization of low power systems because of its easy controllability for the power gating mode.