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

Area of Science:

• Electrical Engineering
• Computer Engineering

Background:

• Traditional nonvolatile flip-flop (NV-FF) designs often employ complex circuits for offset cancellation.
• These complex designs, particularly those using switches, are inefficient for offset cancellation in near/subthreshold voltage regions, as switches exacerbate offset voltage issues.

Purpose of the Study:

• To propose a novel and simplified sensing circuit for NV-FFs operating in low voltage regions.
• To improve the restore yield of NV-FFs by addressing the limitations of complex offset cancellation designs.

Main Methods:

• Introduction of a cross-coupled NMOS-based sensing circuit (CCN-SC).
• The proposed design adheres to a 'simplest is the best' philosophy for improved performance.
• Experimental validation using a 65 nm test chip.

Main Results:

• The CCN-SC demonstrated a restore yield improvement of over 25 times at a 0.35 V supply voltage compared to cross-coupled inverter-based sensing circuits.
• This improvement was achieved in NV-FFs operating in the near/subthreshold voltage region.
• The proposed circuit exhibited 18 times higher power consumption.

Conclusions:

• The novel CCN-SC offers a significant improvement in restore yield for NV-FFs at low operating voltages.
• The simplified design approach proves effective where complex methods fail.
• While power consumption is higher, the yield enhancement addresses a critical challenge in subthreshold operation.