臺灣博碩士論文加值系統

為了要達到降低成本與高精準度的需求，本論文提出了一種互補式金氧半積體電路之對消式溫度感測器的設計。此設計的重點是針對整個電路中的能隙參考電壓電路(bandgap reference circuit)和正比於絕對溫度之電壓電路(PTAT circuit)這兩個部分做了降低電路中運算放大器之輸入偏移電壓(offset voltage of operational amplifier)的改良。如此一來，在沒有校調的情況下，就有很好的輸出線性度，亦可降低校正成本。
此溫度感測器之電路中使用寄生雙載子電晶體(bipolar transistor)作為一個溫度的感測的單元，為了要消除所使用運算放大器之輸入偏移電壓所造成的不良影響，在能隙參考電壓電路與正比於絕對溫度之電壓電路的設計中我們使用了對消穩定的電路方法(chopper stabilization technique)來降低運算放大器的輸入偏移電壓並且維持其輸出電壓的精準度。整個電路是使用雙金屬0.6微米的互補式金氧半積體電路製程來製造，整個電路的面積大約是1.3毫米平方，此電路在不需要任何校調的情況下，針對能隙參考電壓電路和正比於絕對溫度之電壓電路，在-55到125�aC的溫度範圍所量到的精準度為3.5�aC，且因為不需要校調就有很好的線性度，所以只需在一個溫度作校正，可以降低測試成本。整個電路的正常供應電壓為3.3伏特，供應電流為150微安培。在論文中對於能隙參考電壓電路和正比於絕對溫度之電壓電路的設計與量測結果有詳細的討論。

A CMOS chopper temperature sensor is present. Accurate bandgap reference and PTAT voltage are designed. The circuit uses substrate bipolar transistors as a temperature sensing element. In order to reduce the effect of the offset voltage of the operational amplifier in the circuit, we use the chopper stabilization technique to eliminate the offset voltage. The complete system is realized in a double metal 0.6�慆 CMOS process, and the chip size is 1.3mm2. In the temperature range from -55 to 125�aC, the total inaccuracy of bandgap reference and PTAT voltage is 3.5�aC without calibration. The circuit operates at a typical supply voltage, 3.3V, and its supply current is 150�嫀. Experiment results of the bandgap reference and PTAT voltage and simulated design of the circuit are discussed in this thesis.

List of Contents
English Abstract……………………………………………………………….. i
Chinese Abstract………………………………………………………………. ii
Acknowledgement……………………………………………………………… iii
List of Contents………………………………………………………………… iv
List of Figures………………………………………………………………….. vi
List of Tables…………………………………………………………………… viii
Chapter1 Introduction
1.1 Background and Motivation………………………………………………. 1
1.2 Research Goals and Thesis Organization…………………………………. 2
Chapter2 Review of Temperature Sensors
2.1 Introduction of Temperature Sensors……………………………………... 4
2.2 Parameters of Temperature Sensor………………………………………... 4
2.2.1 Temperature Range…………………………………………………… 5
2.2.2 Accuracy……………………………………………………………… 5
2.2.3 Calibration and Trimming……………………………………………. 5
2.3 Introduction of Temperature Sensors……………………………………... 5
2.4 PTAT Source………………………………………………………………. 6
2.4.1 VBE Generator………………………………………………………… 6
2.4.2 Operation Principle…………………………………………………… 7
2.4.3 Accuracy……………………………………………………………… 8
2.5 Bandgap Reference………………………………………………………... 8
2.5.1 Conventional bandgap Voltage Reference……………………………. 9
2.5.2 Errors in CMOS Bandgap Reference………………………………… 9
Chapter3 Design Issues of CMOS Temperature Sensors
3.1 CMOS Bandgap Reference and PTAT Design……………………………. 16
3.2 Dynamic Offset Cancellation Techniques………………………………… 16
3.2.1 Autozero Technique………………………………………………….. 16
3.2.2 Chopper Technique…………………………………………………… 17
3.3 Dynamic Element Matching Techniques………………………………….. 18
3.4 Target Specifications of the Bandgap Reference and PTAT Voltage……… 19
Chapter4 CMOS Chopper Temperature
4.1 Design of CMOS Chopper Bandgap Reference…………………………... 26
4.1.1 Principle………………………………………………………………. 26
4.1.2 Low Pass Filter……………………………………………………….. 26
4.2 CMOS Chopper Bandgap Reference with Internal Low-pass Filter……… 28
4.2.1 Principle………………………………………………………………. 28
4.2.2 Simulation Results……………………………………………………. 28
4.3 PTAT Generator…………………………………………………………… 29
4.3.1 Principle………………………………………………………………. 29
4.3.2 Chopped Instrumentation Amplifier………………………………….. 29
4.3.3 S/H Circuit Design…………………………………………………… 30
4.3.4 Simulation Results……………………………………………………. 31
Chapter5 Experiment Results and Discussions
5.1 Experiment Results………………………………………………………... 47
5.1.1 Bandgap Reference Voltage…………………………………………... 47
5.1.2 PTAT Voltage…………………………………………………………. 48
5.2 Discussions………………………………………………………………... 48
Chapter6 Conclusion and Future Work
6.1 Conclusions……………………………………………………………….. 56
6.2 Future Work……………………………………………………………….. 56
REFERENCE………………………………………………………………….. 58

List of Figures

Figure 1-1. Principle of thermal management in a computer system…………. 3
Figure 2-1. Block diagram of a typical temperature sensor…………………... 11
Figure 2-2. Substrate PNP transistor in twin-well CMOS technology……….. 12
Figure 2-3. Base-emitter voltage VBE versus temperature T………………….. 13
Figure 2-4. Principle of a PTAT source……………………………………….. 14
Figure 2-5. Conventional CMOS bandgap reference…………………………. 15
Figure 3-1. Basic schematic for a CMOS bandgap reference circuit…………. 21
Figure 3-2. A basic autozeroing stage………………………………………… 22
Figure 3-3. Amplifier using the chopper stabilization technique, and signals
illustrated in both the frequency and time domain……………… 23
Figure 3-4. Residual offset caused by spikes
(a) Spike signal (b) demodulation signal (c) demodulation spike... 24
Figure 3-5 Generation of VPTAT using DEM………………………………….. 25
Figure 4-1(a). Chopper circuit design…………………………………………... 32
Figure 4-1(b). CMOS chopper bandgap reference circuit……………………… 33
Figure 4-2. CMOS chopper bandgap reference with a RC low pass filter……. 34
Figure 4-3. CMOS chopper bandgap reference with a SC low pass filter……. 35
Figure 4-4. Schematic of the conventional CMOS chopper bandgap voltage
reference…………………………………………………………. 36
Figure 4-5. Reference output voltage under different chopping frequencys….. 37
Figure 4-6. Simulated Vref for overly high chopping frequency……………… 38
Figure 4-7. Schematic of the PTAT generator………………………………… 39
Figure 4-8. Instrumentation amplifier for PTAT voltage……………………… 40
Figure 4-9. Instrumentation amplifier with chopper………………………….. 41
Figure 4-10. Sample/hold circuit for chopped signal…………………………… 42
Figure 4-11. Timing diagram for sample/hold circuit…………………………... 43
Figure 4-12. Temperature analysis of VPTAT,O…………………………………… 44
Figure 4-13. Transient response of V�SPTAT………………………………………. 45
Figure 4-14. Transient response of VPTAT………………………………………. 46
Figure 5-1. Layout diagram…………………………………………………… 50
Figure 5-2. Temperature characteristic of bandgap voltage reference with
different chopping frequency……………………………………. 51
Figure 5-3. Temperature characteristic of bandgap voltage reference of
TEMP1………………………………………………………….. 52
Figure 5-4. Temperature characteristic of bandgap voltage reference of 6
samples…………………………………………………………… 53
Figure 5-5. Temperature characteristic of PTAT voltage of TEMP4………….. 54
Figure 5-6. Temperature characteristic of PTAT voltage of 6 samples……….. 55









List of Tables

Table 2-1. Errors in CMOS bandgap reference………………………………. 10
Table 3-1. Target specifications of the bandgap reference and PTAT voltage... 20
Table 5-1. Comparison of target specifications and experiment results………. 49

REFERENCE

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[12] A Bakker, Kevin Thiele, Johan Huijsing, “A CMOS Nested Chopper Instrumentation Amplifier with 100nV Offset”, IEEE International Solid-State Circuit Conference 2000

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[14] National Semiconductor, “LM75-Digital Temperature Sensor and Thermal Watchdog with Two-Wire Interface”, http:// www.national.com, November 1999

[15] A Bakker, Johan H Huijsing, “Micropower CMOS Temperature Sensor with Digital Output”, IEEE Journal of Solid-State Circuit, vol.31 No.7, July 1996

[16] Adel S. Sedra, Kenneth C. Smith, “Microelectronic Circuit”, New York Oxford 1998

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[18] Peter R. Hollowway, Ravi Subrahamayan, Gray E. Sheehan, “Linearized Temperature Sensor”, US patent 6,183,131 B1