Thiết Kế Bộ Chuyển Đổi Tương Tự - Số 12 Bits Sar-Adc Nhằm Cải Thiện Hiệu Năng Màn Hình Tft.pdf

ĐẠI HỌC QUỐC GIA HÀ NỘITRƯỜNG ĐẠI HỌC CÔNG NGHỆ Nguyễn Tuấn Anh THIẾT KẾ BỘ CHUYỂN ĐỔI TƯƠNG TỰ - SỐ 12 BITS SAR-ADC NHẰM CẢI THIỆN HIỆU NĂNG MÀN HÌNH TFT KHÓA LUẬN TỐT NGHIỆP ĐẠI HỌC HỆ

ĐẠI HỌC QUỐC GIA HÀ NỘI

TRƯỜNG ĐẠI HỌC CÔNG NGHỆ

Nguyễn Tuấn Anh

THIẾT KẾ BỘ CHUYỂN ĐỔI TƯƠNG TỰ - SỐ

12 BITS SAR-ADC NHẰM CẢI THIỆN HIỆU NĂNG MÀN HÌNH TFT

KHÓA LUẬN TỐT NGHIỆP ĐẠI HỌC HỆ CHÍNH QUYNgành: Công nghệ kỹ thuật điện tử truyền thông

HÀ NỘI – 2023

ĐẠI HỌC QUỐC GIA HÀ NỘITRƯỜNG ĐẠI HỌC CÔNG NGHỆ

Nguyễn Tuấn Anh

THIẾT KẾ BỘ CHUYỂN ĐỔI TƯƠNG TỰ - SỐ

12 BITS SAR-ADC NHẰM CẢI THIỆN HIỆU NĂNG MÀN HÌNH TFT

KHÓA LUẬN TỐT NGHIỆP ĐẠI HỌC HỆ CHÍNH QUYNgành: Công nghệ kỹ thuật điện tử truyền thông

Cán bộ hướng dẫn: PGS.TS Mai Anh Tuấn

HÀ NỘI - 2023

VIETNAM NATIONAL UNIVERSITY, HANOI

UNIVERSITY OF ENGINEERING AND TECHNOLOGY

Nguyen Tuan Anh

DESIGN 12-BIT SUCCESSIVE-APPROXIMATION DIGITAL-TO-ANALOG CONVERTER (SAR-ADC) TOWARD AN IMPROVEMENT OF TFT DISPLAY

PERFORMANCE

Major: Faculty of Electronics and Telecommunications

Supervisor: Assoc Prof Mai Anh Tuan

HA NOI - 2023

TÓM TẮT NỘI DUNG

Tóm tắt: Ngày nay, trong thế giới của các dụng cụ đo lường khoa học, hầu như tất cả các kếtquả đo lường đều được số hoá, tức là được chuyển đổi sang miền kĩ thuật số Đầu ra tương tựcủa các cảm biến như cặp nhiệt điện, máy đo biến dạng, máy đo gia tốc, cảm biến lực vàchuyển vị, v.v., được số hoá cho mục đích ghi, hiển thị và phân tích Máy tính kĩ thuật số cóthể tương tác với các tín hiệu phổ biến này nhờ chuyển đổi tương tự sang kĩ thuật số Bộchuyển đổi tương tự sang số là bộ chuyển đổi tín hiệu tương tự sang tín hiệu số, gọi tắt làADC ( Analog to Digital Converter) Có rất nhiều loại ADC trên thị trường, trong đó có SAR-ADC, loại này có nhiều ưu điểm hơn các loại ADC khác, nó có độ chính xác cao và tiêu thụđiện năng thấp Do có độ chính xác cao nên SAR-ADC thường được dùng để cải thiện hiệunăng cho các loại màn hình cảm ứng điện trở có trên thị trường Loại màn hình cảm ứng điệntrở là loại màn hình cảm ứng đơn điểm, nhược điểm của loại màn hình này là có độ trễ khálớn và độ chính xác không cao SAR-ADC hoàn toàn có thể khắc phục những nhược điểm đótrên màn hình cảm ứnng điện trở, cụ thể là màn hình TFT

Từ khóa: SAR-ADC

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Abstract: Today, in the world of scientific measuring instruments, almost all measurementresults are digitized, i.e converted to the digital domain Analog outputs of sensors such asthermocouples, strain gauges, accelerometers, force and displacement sensors, etc., aredigitized for recording, display and analysis purposes Digital computers can interact withthese common signals by converting analog to digital An analog to digital converter is ananalog to digital converter, referred to as ADC (Analog to Digital Converter) There are manytypes of ADCs on the market, including SAR-ADC, which has many advantages over otherADCs, it has high accuracy and low power consumption Due to its high accuracy, SAR-ADC

is often used to improve the performance of resistive touch screens on the market Resistivetouch screen type is a single-point touch screen, the disadvantage of this type of screen is that

it has a large delay and is not accurate SAR-ADC can completely overcome thosedisadvantages on resistive touch screens, specifically TFT display

Keywords: SAR-ADC

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First of all, I would like to express my sincere and deep gratitude to Assoc Prof.Mai Anh Tuan for his dedicated guidance and advice, providing valuable experiencesfor me during the time of researching and carrying out my thesis

I also want to express my sincere thanks to the teachers in the University ofEngineering and Technology for creating opportunities for me to study and developmyself during my four years at the school, helping me acquire the basic skills to beable to complete my thesis Furthermore, having these skills prepared me to take onthe world with confidence

Although I have tried my best, my graduation thesis cannot avoid someshortcomings I respectfully request the teachers and friends to provide suggestions toimprove my thesis

Finally, I wish the teachers and everyone good health and success in their life andteaching careers, and to prepare the next generation of knowledgeable citizens for thecountry

Thank you very much!

Student

Nguyen Tuan Anh

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LỜI CAM ĐOANTôi xin cam đoan đề tài “Thiết kế bộ chuyển đổi tương tự - số 12 bit SAR-ADCnhằm cải thiện hiệu năng của màn hình TFT ” là khóa luận tốt nghiệp do chính bảnthân mình thực hiện trong suốt thời gian vừa qua dưới sự hướng dẫn của PGS.TS MaiAnh Tuấn Những số liệu và kết quả nghiên cứu là hoàn toàn trung thực và không saochép của người khác mà không chỉ rõ về mặt tài liệu tham khảo Nếu không đúng sựthật, tôi xin chịu hoàn toàn trách nhiệm.

Hà Nội, ngày…tháng…năm 2023

Sinh viên

Nguyễn Tuấn Anh

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TÓM TẮT NỘI DUNG i

ABSTRACT ii

ACKNOWLEDGMENTS iii

LỜI CAM ĐOAN iv

CONTENTS v

IMAGE CATALOG vii

LIST OF TABLES ix

PREFACE 1

CHAPTER 1 INTRODUCTION 4

1.1 Overview of ADC 4

1.1.1 History of ADC 6

1.1.2 Type of ADC 10

1.2 Overview of SAR-ADC 14

1.3 Overview of TFT Display 15

1.3.1 What is TFT screen? 15

1.3.2 Advantages and disadvantages of TFT screens compared to other screens 16

1.3.3 Application of TFT 17

1.4 The impact of ADC on the performance of TFT Display 18

1.5 Compare SAR ADC and conventional ADC 19

1.6 Objective 19

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CHAPTER 2 LITERATURE REVIEW 21

CHAPTER 3 DESIGN 24

3.1 SAR ADC architecture and operation 24

3.2 Sample and Hold circuit 25

3.2.1 Cmos Technology 27

3.2.2 Bootstrapped sample and hold circuit 29

3.3 Digital Analog Converter circuit 30

3.3.1 Split capacitor Digital to Analog Converter 35

3.3.2 Perform 36

3.4 Comparator circuit 36

3.4.1 Comparative Criteria 40

3.5 Successive-Approximation-Register control logic block 41

3.5.1 D flip-flops with Set/Reset 42

3.5.2 Perform 43

CHAPTER 4 RESULTS AND CONCLUSIONS 46

4.1 RESULTS 46

4.1.1 Sample and Hold 46

4.1.2 Digital to Analog converter 46

4.1.3 Comparator 47

4.1.4 SAR 48

4.2 CONCLUSION 50

REFERENCES 52

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IMAGE CATALOG

Figure 1: Vacuum Tubes 6

Figure 2: Typical example of Nyquist frequency and rate 7

Figure 3: Early telegraph machine 8

Figure 4: Electronic magazine, Jun 1954-The silicon transister 8

Figure 5: Block diagram of the Delta-sigma ADCs 11

Figure 6: Showing the comparator, timer, and controller 12

Figure 7: Pipelined ADC illustration 13

Figure 8: Block diagram of the SAR-ADC 15

Figure 9: TFT LCD Display Layer 16

Figure 10: Application of TFT 17

Figure 11: SAR-ADC blocks 22

Figure 12: A 3-bit SAR ADC example 23

Figure 13: Sample and Hold simulation 24

Figure 14:Basic Track & Hold (T&H) circuit 25

Figure 15: NMOS pass gate and a PMOS pass gate 27

Figure 16:Working principle of Bootstrapped 28

Figure 17: Operation diagram of DAC block 30

Figure 18: DAC block simulation 30

Figure 19: DAC classification 32

Figure 20: Structure of Split Capacitor DAC 33

Figure 21: Switches of capacitors 34

Figure 22: Comparator block simulation 36

Figure 23: Positive feedback decision circuit 37

Figure 24: Self bias buffer 37

Figure 25: Pre-amplifier 37

Figure 26: SAR block simulation 39

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Figure 27: Successive-Approximation-Register control logic block 40

Figure 28: D Flip-flop circuit which uses NAND gate 3-to-1 to build up this structure 41

Figure 29: Simulation the Sample and Hold 44

Figure 30: Simulation DAC with Vin = 600mV, Vref = 1V 45

Figure 31: Simulation Comparator with Vin = 600mV, Vref = 1V 45

Figure 32: Simulation SAR control logic with Vin = 600mV, Vref = 1V 46

Figure 33: Simulation SAR control logic with Vin = 900mV, Vref = 1V 47

Figure 34: Simulation SAR control logic with Vin = 700mV, Vref = 1V 47

Figure 35: Simulation SAR control logic with Vin = 600mV, Vref = 1V 48

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LIST OF TABLES

Table 1: First Row Register Outputs 42Table 2: Second Row Outputs 42

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The meaning of the topic

The SAR ADC digital-to-analog converter aims to optimize the conversionfrom analog signal to digital signal in TFT display This converter will help improveimage quality, increase processing speed and reduce errors in the conversion process.The project "Designing a SAR ADC digital-to-analog converter to improve TFTdisplay performance" tries to solve performance problems in converting analog todigital signals on TFT screens A SAR ADC digital-to-analog converter is used toimprove the signal quality and ensure the accuracy of the output signal

In addition to improving performance, SAR ADC digital-to-analog convertersalso help save costs and reduce complexity in the manufacturing process

Through the implementation of this topic, it is desired to solve the problems of signalconversion on TFT screens and provide users with a better experience in using TFTscreens

Content of the topic

Theses “Design 12-Bit Successive-Approximation Digital-To-Analog Converter(SAR-ADC) Toward An Improvement of TFT Display Performance” will describe,design and test a SAR ADC digital-to-analog converter that can improve theperformance of the TFT Specifically, the accuracy, mode and power consumption ofthe TFT

Objective

In order to enhance the performance of TFT, I shall create an analog to digitalconverter in my thesis Therefore, ideal power and excellent resolution are needed TheAnalog-to-Digital Converters of Consecutive Approximation are the most appropriateADC to meet the criteria, according to section 1.2 analysis of the benefits anddrawbacks of ADCs

My goal is not only to develop a low power 12-bit sequential approximation Analog toDigital Converter (SAR-ADC) based on CMOS technology (90nm protocol) withinternal voltage reference + 2.5V, 10ms transition time, basic features of SAR ADC,including Differential Nonlinearity – DNL (1 LSB) and Integral Nonlinearity – INL (1LBS), were measured, but also to cultivate more knowledge about integrated circuitdesign such as design diagram, digital design, simulation, IC layout, basic knowledge

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A standard comparator circuit has two inputs: an analog input signal and a DACoutput signal Based on the comparison of these two input signals, the comparatorcircuit provides a digital output signal If the DAC output signal exceeds the inputsignal, the comparator produces a digital output of '0,' indicating that the DAC outputvoltage should be reduced If the DAC output signal is less than the input signal, thecomparator outputs a digital value of '1,' indicating that the DAC output voltage should

be increased

The precision and speed of the comparator circuit are essential variables indetermining the overall performance of the SAR ADC The offset voltage, hysteresis,and noise of the comparator circuit determine its accuracy When the input signals areequal, the offset voltage is the voltage difference between the comparator's inputterminals The difference in voltage levels at which the comparator flips from high tolow and low to high is referred to as hysteresis The random variation in thecomparator's output voltage caused by internal and external sources is referred to asnoise

Several strategies for optimizing the performance of the comparator circuit havebeen devised Offset voltage, for example, can be reduced by designing the comparatorcircuit using symmetrical input transistors By incorporating feedback into thecomparator circuit, hysteresis can be reduced Noise can be reduced by using low-noise amplifiers and filtering techniques in the comparator circuit design Thecomparator circuit in modern SAR ADCs is frequently developed utilizing advancedtechniques like as dynamic comparators, latch comparators, and regenerativecomparators These modern comparator circuits are built for high accuracy, fast speed,and low power consumption

To summarize, the comparator circuit is an important component of the SARADC and has a substantial impact on the ADC's overall performance Researchers andengineers will continue to explore new and inventive techniques to developingcomparator circuits that improve the performance of SAR ADCs in diverseapplications as technology advances.Comparator circuits are built with high precision,fast speed, and low power consumption in mind

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Figure 22: Comparator block simulation

A SAR ADC's comparator circuit can be implemented using a variety ofamplifier circuits, including open-loop amplifiers, folded-cascode amplifiers, and two-stage amplifiers The open-loop amplifier is the most basic, but its performance islimited due to its low gain and bandwidth Higher gain and bandwidth are provided bythe folded-cascode amplifier and the two-stage amplifier, but they are more complexand consume more power.[30]

Figure 23: Positive feedback decision circuit

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Figure 24: Self bias buffer

Figure 25: Pre-amplifier

To achieve high resolution and accuracy in SAR ADCs, the comparator circuitshould have a high gain, high speed, and a low offset voltage Furthermore, to reducepower consumption, the comparator circuit should be designed to operate at lowsupply voltages[31]

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The main calculation formula used in the block as:

In there:

- Vout is the output of the comparator block

- VREF is the reference voltage of the DAC block

- D is the bit being compared during sampling

- Vin is the input voltage from the DAC block

- Vcm is the common voltage of the comparator block

The above formula allows to compare the input voltage from the DAC block with

a threshold set by adjusting D If the input voltage is greater than the threshold, theoutput of the comparator block will be "1", otherwise it will be "0" Therefore, thisformula along with other parameters of the SAR ADC affects its accuracy andresolution

3.4.1 Comparative Criteria

The comparator is an important component in SAR ADC because it comparesthe input voltage to a reference voltage and generates a digital output based on theresult of the comparison The characteristics of the comparator can have a significantimpact on the SAR ADCs overall performance Some of the important comparatorcharacteristics in SAR ADC are:

- Input offset voltage: The minimum voltage difference required between theinput and the reference voltage to change the comparator's output state A lowinput offset voltage reduces the output error of the comparator [32]

- Input offset drift: Input offset drift is the change in the input offset voltage overtime and temperature A low input offset drift ensures that the comparator'soutput remains stable over a wide range of temperatures and operatingconditions[33]

- Input common-mode range: Input common-mode range is the range of inputvoltages that the comparator can handle without saturating or producing anincorrect output A wide input common-mode range ensures that the comparatorcan handle a broad range of input signals[34]

- Propagation delay: Propagation delay is the time it takes for the comparator tochange its output state after the input voltage changes A low propagation delay

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