Abstract
This study introduces an all-digital CMOS time-domain smart temperature sensor (STS) that offers a smaller circuit area and reduced complexity. In contrast to previous studies that utilized multiple delay lines or additional path selection circuits, the proposed new structure employs a single cyclic path and fewer delay lines. The functionality of high-resolution temperature sensing, pulse-shrinking time measurement, and built-in offset-error cancellation is achieved using only one cyclic delay line (CDL). The temperature-sensing delay line generates a thermal-dependent pulse width proportional to the absolute temperature (PTAT). Subsequently, a pulse-shrinking unit, implemented within the pulse-shrinking delay line, performs time-to-digital conversion by measuring the PTAT pulse width. Finally, a time-added delay line within the CDL incorporates a simple D-type Flip Flop to enable concise offset-error cancellation, thereby improving accuracy. This study further simplifies the cancellation circuitry to reduce the overall circuit area. The proposed sensor, fabricated using a TSMC \(0.35\mu m\) CMOS process, occupies an area of \(0.022 \text {mm}^2\), providing a cost-effective solution for pulse-shrinking STSs. The maximum inaccuracy after offset-error cancellation is \(1.3 ^\circ \)C within a temperature range of \(0 \sim 80 ^\circ \)C, with a high resolution of approximately \(0.035 ^\circ \)C/LSB. This resolution enhancement significantly surpasses similar studies. By reducing circuit complexity, the proposed sensor successfully achieves improvements in both area and resolution.
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Not applicable. Since the proposed in this paper is a smart sensor, all the input–output data are obtained by the chip measurement procedure as stated in the context.
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Acknowledgements
This work was financially supported by National Science and Technology Council (NSTC) of Taiwan for Grants MOST 110-2221-E-992-094, MOST 110-2221-E-992-003, and NSTC 112-2221-E-992-071-. The authors would like to express their appreciation to Taiwan Semiconductor Research Institute (TSRI) for supporting EDA tools and chip fabrication.
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Chen, CC., Chen, CL., Chu, YC. et al. An Area-Effective High-Resolution All-Digital CMOS Time-Domain Smart Temperature Sensor. Circuits Syst Signal Process 43, 1144–1156 (2024). https://doi.org/10.1007/s00034-023-02507-y
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DOI: https://doi.org/10.1007/s00034-023-02507-y