Abstract
This paper presents a novel CMOS wireless temperature sensor design in order to improve the sensitivity and linearity of our previous work on such devices. Based on the principle of CMOS double zero temperature coefficient (DZTC) points, a combined device is first created at the chip level with two voltage references, one current reference, and one temperature sensor. It was successfully fabricated using the 0.35 μm CMOS process. According to the chip results in a wide temperature range from −20 °C to 120 °C, two voltage references can provide temperature-stable outputs of 823 mV and 1,265 mV with maximum deviations of 0.2 mV and 8.9 mV, respectively. The result for the current reference gives a measurement of 23.5 μA, with a maximum deviation of 1.2 μA. The measurements also show that the wireless temperature sensor has good sensitivity of 9.55 mV/°C and high linearity of 97%. The proposed temperature sensor has 4.15-times better sensitivity than the previous design. Moreover, to facilitate temperature data collection, standard wireless data transmission is chosen; therefore, an 8-bit successive-approximation-register (SAR) analog-to-digital converter (ADC) and a 433 MHz wireless transmitter are also integrated in this chip. Sensing data from different places can be collected remotely avoiding the need for complex wire lines.
Highlights
Reference devices, such as voltage and/or current references, are key elements in many mixed-signal and analog applications
Lakdawala [3] used the ratio of currents driven into a bipolar junction transistors (BJTs) pair with current chopping to up-convert the temperature signal and cancel the effects of parasitic resistance
The proposed wireless temperature sensor has been tested in a MC-810 Mini-Subzero temperature chamber provided by Integrated Service Technology (IST) and the experimental setup has been established to test the sensitivity and linearity of the wireless temperature sensor, as shown in TSENSOR, SAR analog-to-digital converter (ADC), on-off keying (OOK) TX, and Regulator blocks
Summary
Reference devices, such as voltage and/or current references, are key elements in many mixed-signal and analog applications. Based on parasitic bipolar transistors display inaccuracies as low as a few tenths of a degree over the military temperature range, i.e., from −55 °C to 125 °C, but require a one-point trim. In our previous design [11], based on the CMOS PTAT principle, a combined device for voltage reference and temperature sensors was successfully implemented using a fully digital process. In order to improve the measurement range, linearity, and sensitivity of our previous design using the PTAT principle, a new DZTC-based temperature sensor design is proposed for performance enhancement. Based on the principle of CMOS DZTC points, a combined device is first created at the chip level with two voltage references, one current reference, and one temperature sensor.
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