Extracting device-parameter variations using a single sensitivity-configurable ring oscillator

The RO(Ring-Oscillator)-based sensor is one of easily-implementable variation sensors, but for decomposing the observed variability into multiple unique device-parameter variations, a large number of ROs with different structures and sensitivities to device-parameters is required. This paper proposes a scheme for sensing multiple device-parameter variations with just a single reconfigurable RO. This sensitivity-configurable RO has a number of configurations available and this property can be exploited for reducing sensor area while improving estimation accuracy through iterative estimation. To minimize the prospective error, the proposed estimation iterates: (1) selecting the best configuration that minimizes the prospective estimation error around the current estimates; and (2) updating the estimates with the selected configuration. This experiment was carried out assuming a 32-nm predictive technology model. Experimental results show that device-parameter extraction with a single RO is feasible and the error of the extracted parameters is reduced by 35 to 53% with the improved objective function and iterative estimation.