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Sensors 2016, 16(2), 176;

All-Digital Time-Domain CMOS Smart Temperature Sensor with On-Chip Linearity Enhancement

Department of Electronic Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung 81146, Taiwan
Author to whom correspondence should be addressed.
Academic Editor: Vittorio M. N. Passaro
Received: 17 December 2015 / Revised: 21 January 2016 / Accepted: 26 January 2016 / Published: 30 January 2016
(This article belongs to the Section Physical Sensors)
Full-Text   |   PDF [2945 KB, uploaded 30 January 2016]   |  


This paper proposes the first all-digital on-chip linearity enhancement technique for improving the accuracy of the time-domain complementary metal-oxide semiconductor (CMOS) smart temperature sensor. To facilitate on-chip application and intellectual property reuse, an all-digital time-domain smart temperature sensor was implemented using 90 nm Field Programmable Gate Arrays (FPGAs). Although the inverter-based temperature sensor has a smaller circuit area and lower complexity, two-point calibration must be used to achieve an acceptable inaccuracy. With the help of a calibration circuit, the influence of process variations was reduced greatly for one-point calibration support, reducing the test costs and time. However, the sensor response still exhibited a large curvature, which substantially affected the accuracy of the sensor. Thus, an on-chip linearity-enhanced circuit is proposed to linearize the curve and achieve a new linearity-enhanced output. The sensor was implemented on eight different Xilinx FPGA using 118 slices per sensor in each FPGA to demonstrate the benefits of the linearization. Compared with the unlinearized version, the maximal inaccuracy of the linearized version decreased from 5 °C to 2.5 °C after one-point calibration in a range of −20 °C to 100 °C. The sensor consumed 95 μW using 1 kSa/s. The proposed linearity enhancement technique significantly improves temperature sensing accuracy, avoiding costly curvature compensation while it is fully synthesizable for future Very Large Scale Integration (VLSI) system. View Full-Text
Keywords: CMOS; smart temperature sensor; time domain; linearity enhancement; field programmable gate array (FPGA) CMOS; smart temperature sensor; time domain; linearity enhancement; field programmable gate array (FPGA)

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Chen, C.-C.; Chen, C.-L.; Lin, Y. All-Digital Time-Domain CMOS Smart Temperature Sensor with On-Chip Linearity Enhancement. Sensors 2016, 16, 176.

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