Abstract

This paper investigates the concepts, performance and limitations of temperature sensing circuits realized in complementary metal-oxide-semiconductor (CMOS) silicon on insulator (SOI) technology. It is shown that the MOSFET threshold voltage (Vt) can be used to accurately measure the chip local temperature by using a Vt extractor circuit. Furthermore, the circuit’s performance is compared to standard circuits used to generate an accurate output current or voltage proportional to the absolute temperature, i.e., proportional-to-absolute temperature (PTAT), in terms of linearity, sensitivity, power consumption, speed, accuracy and calibration needs. It is shown that the Vt extractor circuit is a better solution to determine the temperature of low power, analog and mixed-signal designs due to its accuracy, low power consumption and no need for calibration. The circuit has been designed using 1 µm partially depleted (PD) CMOS-SOI technology, and demonstrates a measurement inaccuracy of ±1.5 K across 300 K–500 K temperature range while consuming only 30 µW during operation.

Highlights

  • Smart integrated temperature sensors and circuits are the main building blocks in all analog and mixed-signal applications, as well as in high-performance systems-on-chip (SoCs)

  • We address the aforementioned challenges by demonstrating the design and successful implementation of a small, low-power, and accurate on chip temperature sensing circuit based on “Threshold Voltage Thermometry” [14], namely a threshold voltage (Vt ) extractor circuit

  • The performance of the Vt extractor circuit is compared to a standard circuit used for temperature sensing, i.e., proportional to absolute temperature (PTAT) circuit, in terms of sensitivity, linearity, speed, accuracy, calibration needs, area and sensor power consumption

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Summary

Introduction

Smart integrated temperature sensors and circuits are the main building blocks in all analog and mixed-signal applications, as well as in high-performance systems-on-chip (SoCs). Sensors 2018, 18, 1629 fabrication (CMOS-SOI compatibility), low cost, high accuracy and sensor linearity in the desired temperature range Following these requirements, various on-chip temperature-sensing circuit have been reported in the literature. The performance of the Vt extractor circuit is compared to a standard circuit used for temperature sensing, i.e., PTAT circuit, in terms of sensitivity, linearity, speed, accuracy, calibration needs, area and sensor power consumption. Both circuits were designed using 1 μm PD CMOS-SOI technology [15]. Technology based on (a) the exponential dependence of vertical PN diodes; (b) Polysilicon resistors

Principle of Operation
B I where n is the number of parallel connected
Implementation
Measurements and Simulations
Simulated
Vt Extractor Circuit
Analysis of Vt Extracting Block
Analysis of Offset Generator
Analysis of Feedback Block
Comparison of of thethe measured and simulate
Findings
Summary
Full Text
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