An Area-Effective High-Resolution All-Digital CMOS Time-Domain Smart Temperature Sensor

• Published in: Circuits, systems, and signal processing systems, and signal processing, 2024-02, Vol.43 (2), p.1144-1156
• Main Authors: Chen, Chun-Chi, Chen, Chao-Lieh, Chu, Yen-Chan, Lin, Guan-Yu
• Format: Article
• Language: English
• Subjects: Cancellation; Circuits; Circuits and Systems; CMOS; Complexity; Delay lines; Electrical Engineering; Electronics and Microelectronics; Engineering; Error analysis; High resolution; Instrumentation; Pulse duration; Sensors; Signal,Image and Speech Processing; Temperature; Temperature sensors; Time domain analysis; Time measurement
• ISSN: 0278-081X; 1531-5878
• DOI: 10.1007/s00034-023-02507-y

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 μ m CMOS process, occupies an area of 0.022 mm 2 , providing a cost-effective solution for pulse-shrinking STSs. The maximum inaccuracy after offset-error cancellation is 1 . 3 ∘ C within a temperature range of 0 ∼ 80 ∘ C, with a high resolution of approximately 0 . 035 ∘ C/LSB. This resolution enhancement significantly surpasses similar studies. By reducing circuit complexity, the proposed sensor successfully achieves improvements in both area and resolution.