Variation resilient adaptive controller for subthreshold circuits

Subthreshold logic is showing good promise as a viable ultra-low-power circuit design technique for power-limited applications. For this design technique to gain widespread adoption, one of the most pressing concerns is how to improve the robustness of subthreshold logic to process and temperature variations. We propose a variation resilient adaptive controller for subthreshold circuits with the following novel features: new sensor based on time-to-digital converter for capturing the variations accurately as digital signatures, and an all-digital DC-DC converter incorporating the sensor capable of generating an operating operating V_dd from 0 V to 1.2 V with a resolution of 18.75 mV, suitable for subthreshold circuit operation. The benefits of the proposed controller is reflected with energy improvement of up to 55% compared to when no controller is employed. The detailed implementation and validation of the proposed controller is discussed.