MTJ-Based State Retentive Flip-Flop With Enhanced-Scan Capability to Sustain Sudden Power Failure

We present two non-volatile flip-flops (NVFFs) that incorporate magnetic tunnel junctions (MTJ) to ensure fast data storage and restoration from intentional and unintentional power outages. The proposed designs also facilitate enhanced scan mode testing capability by exploiting the nonvolatile latch to function as hold latch for delay testing. The proposed NVFF eliminates additional write drivers, and can operate at up to 2 GHz at 1.1 V, with 0.55 pJ of energy consumption in 22 nm predictive technology. We also address the issue of write asymmetry of MTJ through careful transistor upsizing to achieve near uniform write latency. A data-dependent power gating technique is proposed to mitigate the high static current during retention and back-to-back writing of the identical input data. The proposed gated NVFF achieves several orders of magnitude energy saving at the expense of 1.56X area compared to a standard enhanced scan flip-flop.