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Sensors 2013, 13(9), 11439-11452; doi:10.3390/s130911439
Article

A Linearization Time-Domain CMOS Smart Temperature Sensor Using a Curvature Compensation Oscillator

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Received: 12 July 2013; in revised form: 7 August 2013 / Accepted: 16 August 2013 / Published: 28 August 2013
(This article belongs to the Section Physical Sensors)
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Abstract: This paper presents an area-efficient time-domain CMOS smart temperature sensor using a curvature compensation oscillator for linearity enhancement with a −40 to 120 °C temperature range operability. The inverter-based smart temperature sensors can substantially reduce the cost and circuit complexity of integrated temperature sensors. However, a large curvature exists on the temperature-to-time transfer curve of the inverter-based delay line and results in poor linearity of the sensor output. For cost reduction and error improvement, a temperature-to-pulse generator composed of a ring oscillator and a time amplifier was used to generate a thermal sensing pulse with a sufficient width proportional to the absolute temperature (PTAT). Then, a simple but effective on-chip curvature compensation oscillator is proposed to simultaneously count and compensate the PTAT pulse with curvature for linearization. With such a simple structure, the proposed sensor possesses an extremely small area of 0.07 mm2 in a TSMC 0.35-mm CMOS 2P4M digital process. By using an oscillator-based scheme design, the proposed sensor achieves a fine resolution of 0.045 °C without significantly increasing the circuit area. With the curvature compensation, the inaccuracy of −1.2 to 0.2 °C is achieved in an operation range of −40 to 120 °C after two-point calibration for 14 packaged chips. The power consumption is measured as 23 mW at a sample rate of 10 samples/s.
Keywords: curvature compensation; smart temperature sensor; oscillator; time-domain; delay line curvature compensation; smart temperature sensor; oscillator; time-domain; delay line
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Chen, C.-C.; Chen, H.-W. A Linearization Time-Domain CMOS Smart Temperature Sensor Using a Curvature Compensation Oscillator. Sensors 2013, 13, 11439-11452.

AMA Style

Chen C-C, Chen H-W. A Linearization Time-Domain CMOS Smart Temperature Sensor Using a Curvature Compensation Oscillator. Sensors. 2013; 13(9):11439-11452.

Chicago/Turabian Style

Chen, Chun-Chi; Chen, Hao-Wen. 2013. "A Linearization Time-Domain CMOS Smart Temperature Sensor Using a Curvature Compensation Oscillator." Sensors 13, no. 9: 11439-11452.



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