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2006 | Buch

PRECISION TEMPERATURE SENSORS IN CMOS TECHNOLOGY

verfasst von: Michiel A.P. Pertijs, Johan H. Huijsing

Verlag: Springer Netherlands

Buchreihe : Analog Circuits and Signal Processing

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Über dieses Buch

The low cost and direct digital output of CMOS smart temperature sensors are important advantages compared to conventional temperature sensors. This book addresses the main problem that nevertheless prevents widespread - plication of CMOS smart temperature sensors: their relatively poor absolute accuracy. Several new techniques are introduced to improve this accuracy. The effectiveness of these techniques is demonstrated using three prototypes. ? The ?nal prototype achieves an inaccuracy of±0.1 C over the military t- perature range, which is a signi?cant improvement in the state of the art. Since smart temperature sensors have been the subject of academic and industrial research for more than two decades, an overview of existing knowledge and techniques is also provided throughout the book. Inthisintroductorychapter,themotivationandobjectivesofthisworkare- scribed. ThisisfollowedbyareviewofthebasicoperatingprinciplesofCMOS smart temperature sensors, and a brief overview of previous work. The ch- lenges are then described that need to be met in order to improve the accuracy of CMOS smart temperature sensors while maintaining their cost advantage. Finally, the structure of the rest of the book is introduced.

Inhaltsverzeichnis

Frontmatter
1. INTRODUCTION
Abstract
The low cost and direct digital output of CMOS smart temperature sensors are important advantages compared to conventional temperature sensors. This book addresses the main problem that nevertheless prevents widespread application of CMOS smart temperature sensors: their relatively poor absolute accuracy. Several new techniques are introduced to improve this accuracy. The effectiveness of these techniques is demonstrated using three prototypes. The final prototype achieves an inaccuracy of ±0.1°C over the military temperature range, which is a significant improvement in the state of the art. Since smart temperature sensors have been the subject of academic and industrial research for more than two decades, an overview of existing knowledge and techniques is also provided throughout the book.
Michiel A.P. Pertijs, Johan H. Huijsing
2. CHARACTERISTICS OF BIPOLAR TRANSISTORS
Abstract
Bipolar transistors form the core of most smart temperature sensors. This chapter reviews the physics of bipolar transistors and the various effects that determine the temperature dependency of their base-emitter voltage. The bipolar transistors available in standard CMOS processes are described and compared. Their most important non-idealities are discussed, including their sensitivity to processing spread and mechanical stress. The models introduced in this chapter will be used extensively in the rest of the book.
Michiel A.P. Pertijs, Johan H. Huijsing
3. RATIOMETRIC TEMPERATURE MEASUREMENT USING BIPOLAR TRANSISTORS
Abstract
The output of a smart temperature sensor is a digital representation of its temperature. This requires a ratiometric temperature measurement: the ratio of a temperature-dependent voltage and a reference voltage is determined using an analog-to-digital converter. This chapter describes how substrate bipolar transistors in CMOS technology can be used to accurately generate these voltages.
Michiel A.P. Pertijs, Johan H. Huijsing
4. SIGMA-DELTA ANALOG-TO-DIGITAL CONVERSION
Abstract
This chapter discusses the design of the analog-to-digital converter (ADC) of a precision smart temperature sensor. This ADC converts the voltages V BE and ΔV BE (generated using the techniques introduced in the previous chapter) to a digital temperature reading. The chapter starts with an overview of the requirements that have to be met in this application. After a brief overview of different types of ADCs, sigma-delta (ΣΔ) ADCs are shown to be particularly suited for the narrow bandwidth signals found in temperature sensors. The system-level design of first- and second-order ΣΔ modulators and the associated decimation filters is discussed. Since dynamic error correction techniques (such as dynamic element matching) are needed to accurately generate V BE and ΔV BE , special attention is paid to the filtering of the associated dynamic error signals.
Michiel A.P. Pertijs, Johan H. Huijsing
5. PRECISION CIRCUIT TECHNIQUES
Abstract
This chapter discusses the circuit implementation of CMOS smart temperature sensors. More specifically, it focusses on the implementation of accurate charge balancing in the sigma-delta ADC. Implementations based on continuous- time and switched-capacitor circuits are discussed. Their performance in terms of noise, accuracy and power consumption is analyzed, and solutions to mismatch- and offset-related errors are presented.
Michiel A.P. Pertijs, Johan H. Huijsing
6. CALIBRATION TECHNIQUES
Abstract
Using the design techniques presented in the previous chapters, many circuitand device-related errors inCMOSsmart temperature sensors can be sufficiently reduced. However, variations in the base-emitter voltage of the bipolar transistors (as a result of process spread and mechanical stress) will ultimately limit the achievable accuracy. Trimming, and an associated calibration procedure, are needed to correct for these variations. If high accuracy is desired, traditional calibration techniques are time-consuming and therefore costly. This chapter presents three alternative calibration techniques that combine accuracy with low production costs: batch calibration, calibration based on ΔV BE measurement, and voltage reference calibration.
Michiel A.P. Pertijs, Johan H. Huijsing
7. REALIZATIONS
Abstract
This chapter describes the realization of three CMOS smart temperature sensors in which the techniques introduced in the previous chapters have been applied. The first two sensors are continuous-time designs in which the most dominant errors–spread and curvature of the base-emitter voltage, and amplifier offset–have been addressed. These sensors have been implemented in a 0.7 μm and 0.5 μm digital CMOS process and achieve an inaccuracy of ±1.5 °C and ±0.5 °C, respectively. The third sensor is a switched-capacitor design in which many more dynamic error correction techniques have been applied. This design will therefore be described in most detail. It has been implemented in a 0.7 μm CMOS process and has an inaccuracy of ±0.1 °C. A comparison with previous work, included at the end of the chapter, shows that this is, to date, the highest reported accuracy.
Michiel A.P. Pertijs, Johan H. Huijsing
8. CONCLUSIONS
Abstract
This final chapter summarizes the main findings of this book. It also shows that some of the techniques developed for smart temperature sensors can also be applied to other applications, and provides an outlook on future work on CMOS smart temperature sensors.
Michiel A.P. Pertijs, Johan H. Huijsing
Backmatter
Metadaten
Titel
PRECISION TEMPERATURE SENSORS IN CMOS TECHNOLOGY
verfasst von
Michiel A.P. Pertijs
Johan H. Huijsing
Copyright-Jahr
2006
Verlag
Springer Netherlands
Electronic ISBN
978-1-4020-5258-3
Print ISBN
978-1-4020-5257-6
DOI
https://doi.org/10.1007/1-4020-5258-8

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