Study on Cross-Coupled-Based Sensing Circuits for Nonvolatile Flip-Flops Operating in Near/Subthreshold Voltage Region

To date, most studies focus on complex designs to realize offset cancelation characteristics in nonvolatile flip-flops (NV-FFs). However, complex designs using switches are ineffective for offset cancelation in the near/subthreshold voltage region because switches become critical contributors to the offset voltage. To address this problem, this paper proposes a novel cross-coupled NMOS-based sensing circuit (CCN-SC) capable of improving the restore yield, based on the concept that the simplest is the best, of an NV-FF operating in the near/subthreshold voltage region. Measurement results using a 65 nm test chip demonstrate that with the proposed CCN-SC, the restore yield is increased by more than 25 times at a supply voltage of 0.35 V, compared to that with a cross-coupled inverter-based SC, at the cost of 18× higher power consumption.