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3์ค ์ํ๋ง ๋ฐฉ์ ๋ธํ-์๊ทธ๋ง ADC๋ฅผ ์ด์ฉํ ๋์งํธ Capacitive MEMS ๋ง์ดํฌ๋กํฐ
ํ์๋
ผ๋ฌธ(๋ฐ์ฌ) -- ์์ธ๋ํ๊ต๋ํ์ : ๊ณต๊ณผ๋ํ ์ ๊ธฐยท์ ๋ณด๊ณตํ๋ถ, 2022. 8. ๊น์ํ.๋ณธ ๋
ผ๋ฌธ์์๋ ํธ๋ฆฌํ ์ํ๋ง ์ ๋ถ๊ธฐ๋ฅผ ์ฌ์ฉํ Capacitive ๋ฐฉ์์ MEMS ๋ง์ดํฌ๋กํฐ์ด ์ ์๋์๋ค. ํธ๋ฆฌํ ์ํ๋ง์ ๋ธํ-์๊ทธ๋ง ๋ฐฉ์์ ์๋ ๋ก๊ทธ-๋์งํธ ๋ณํ๊ธฐ์ ์ฒซ ๋ฒ์งธ ์ ๋ถ๊ธฐ์ ์ฌ์ฉ๋์๊ณ ํฌ๊ฒ ๋ ๊ฐ์ง์ ๋์์ผ๋ก ๊ตฌ๋ถ๋๋ค. ์ฒซ ๋ฒ์งธ๋ก ์ ๋ถ๊ธฐ์ ์
๋ ฅ์์ ๋ฐ์ฃผ๊ธฐ ์ง์ฐ ์ฐจ๋ ์
๋ ฅ์ ๋นผ์ ์ ํธ ํฌ๊ธฐ๋ฅผ 2๋ฐฐ๋ก ๋ง๋ค๋ ๋ฐฉ์. ๋ ๋ฒ์งธ๋ก DAC์ ํผ๋๋ฐฑ ์ปคํจ์ํฐ๋ฅผ ์ํ๋ง ์ปคํจ์ํฐ๋ก ์ฌ์ฉํ์ฌ ์
๋ ฅ ์ ์์ ์ถ๊ฐ๋ก ์ฆ๊ฐ์ํค๋ ๋ฐฉ์์ด๋ค. ์ถ๊ฐ์ ์ผ๋ก ๊ธฐ์กด์์ ์ํ๋ง ์ปคํจ์ํฐ๋ฅผ ์ฆ๊ฐ์์ผ ์ ํธ์ ํฌ๊ธฐ๋ฅผ ์ฆํญ์ํค๋ ๋ฐฉ์๊ณผ ๊ฒฐํฉํ์ฌ ์ค์๋ฐฐ์ ์ด๋์ ์ป์ ์ ์๋ค. ๋ํ ์ถ๊ฐ์ ์ธ ์ปคํจ์ํฐ, ํ์ด๋ฐ, ์ ๋ฅ ์๋ชจ ์์ด ๊ตฌ์กฐ ๋ณ๊ฒฝ๋ง์ผ๋ก ์ด๋ฅผ ๋ฌ์ฑํ์๊ธฐ ๋๋ฌธ์ ๋ณ๋ค๋ฅธ trade-off ์์ด ์ ํธ์ ํฌ๊ธฐ๋ฅผ ์ฆํญ์ํฌ ์ ์์๋ค. ์ถ๊ฐ์ ์ผ๋ก ํธ๋ฆฌํ ์ํ๋ง ๋ฐฉ์์ ์ ๋ถ๊ธฐ ์ ํธ ์ ๋ฌ ํจ์ ๋ฐ ์ก์ ๋ถ์ ๋ํ ํฌํจํ์๋ค.
์ฐ๋ฆฌ์ readout ํ๋ก๋ ๊ณต๊ธ ์ ์์ด 1.8V์ธ 0.18 m CMOS ๊ณต์ ์ผ๋ก ๊ตฌํํ์๊ณ single-ended capacitive MEMS ํธ๋์ค๋์๋ฅผ ์ฌ์ฉํ์ฌ ์ธก์ ํ์๋ค. ์ ๋ฅ ์๋ชจ๋์ 520 ฮผA ์ด๋ค. ๋ง์ดํฌ๋กํฐ์ A-weighted ์ ํธ ๋ ์ก์ ๋น๋ 62.1 dBA, ์ํฅ ๊ณผ๋ถํ ์ง์ ์ 115 dB SPL์ ๋ฌ์ฑํ์๊ณ ์นฉ์ die size๋ 0.98ใ"mm" ใ^2 ์ด๋ค.A triple-sampling ฮฮฃ ADC can replace the programmable-gain amplifier commonly used in the readout circuit for a digital capacitive MEMS microphone. The input voltage can then be multiplied by subtracting a further half-period delayed differential input and using the feedback capacitor of the DAC as a sampling capacitor. This triple-sampling technique results in a readout circuit with sensitivity and noise performance comparable to recent designs, but with a reduced power requirement. CMRR improvement is achieved by subtracting differential inputs and superior noise performance compare to conventional structure, as amplifier noise and DAC kT/C noise is not amplified by triple-sampling structure while the signal is increased by its gain. Triple-sampling also can be operated as a single-to-differential circuit. A MEMS microphone incorporating this readout circuit, fabricated in a 0.18ฮผm CMOS process, achieved an A-weighted SNR of 62.1 dBA at 94 dB SPL with 520 ฮผA current consumption, to which triple-sampling was shown to contribute 4.5 dBA.CHAPTER 1 INTRODUCTION 1
1.1 MOTIVATION 1
1.1.1 MEMS MICROPHONE TRENDS 1
1.1.2 TYPE OF MEMS MICROPHONES 4
1.1.3 PREVIOUS WORKS 7
1.2 MEMS MICROPHONE BASIC TERMS 9
1.3 THESIS ORGANIZATION 12
CHAPTER 2 SYSTEM OVERVIEW 13
2.1 SYSTEM ARCHITECTURE 13
CHAPTER 3 INTERFACE CIRCUITS AND POWER MANAGEMENT CIRCUITS 16
3.1 PSEUDO-DIFFERENTIAL SOURCE FOLLOWER 17
3.2 CHARGE PUMP 19
3.3 LOW DROPOUT REGULATOR 22
3.3.1 DESIGN CONSIDERATION OF LOW DROPOUT REGULATOR 22
3.3.2 IMPLEMENTATION OF LOW DROPOUT REGULATOR 26
CHAPTER 4 TRIPLE-SAMPLING DELTA-SIGMA ADC 31
4.1 BASIC OF DELTA-SIGMA ADC 31
4.2 IMPLEMENTATION OF TRIPLE-SAMPLING DELTA-SIGMA MODULATOR 37
4.2.1 CONVENTIONAL 1ST INTEGRATOR STRUCTURE 37
4.2.2 CROSS-SAMPLING 1ST INTEGRATOR 40
4.2.3 TRIPLE-SAMPLING 1ST INTEGRATOR 43
4.2.4 STF ANALYSIS OF TRIPLE-SAMPLING 1ST INTEGRATOR 47
4.2.5 THERMAL NOISE ANALYSIS OF TRIPLE-SAMPLING 1ST INTEGRATOR 51
4.2 CIRCUIT IMPLEMENTATION OF DELTA-SIGMA ADC 57
CHAPTER 5 MEASUREMENT RESULTS 64
5.1 MEASUREMENT ENVIRONMENT 64
5.2 MEASUREMENT RESULTS 67
5.3 PERFORMANCE SUMMARY 72
CHAPTER 6 CONCLUSION 74
BIBLIOGRAPHY 76
ํ๊ธ์ด๋ก 79๋ฐ