An All-Digital Time-Domain Smart Temperature Sensor With a Cost-Efficient Curvature Correction

This paper presents an all-digital time-domain smart temperature sensor (TDSTS) with a cost-efficient curvature correction, which can effectively improve the accuracy and cost. Inverter-based TDSTSs are low cost and low complexity but they exhibit a significant curvature, which severely impairs their accuracy. Linearity enhancement through linear interpolation reduces the curvature and results in a twofold improvement in the accuracy. In this paper, the proposed curvature correction not only simplified the scheme to reduce the hardware cost but also successfully eliminated the curvature to achieve the most suitable accuracy. In addition, the correction procedure was also simplified. The TDSTS was implemented in eight Xilinx field-programmable gate arrays for performance verification and occupied 74 slices per sensor. The logic utilization for the proposed curvature-corrected circuit was 17 slices, and its cost was only 23% of the hardware cost. The experimental results indicated that the maximum inaccuracy decreased from 5 °C to 1.8 °C over the temperature range of -20 °C-100 °C, resulting in an approximate threefold improvement in the accuracy. Compared with a previous study, the improvements of 30% and 43% in the accuracy and cost, respectively, successfully validate the proposed technique.