隨著近年物聯網應用的興起，可攜式裝置與邊緣運算的研究也跟著蓬勃發展，而在此趨勢當中，低功耗高效能的感測器讀取電路也愈發受到重視，諸如生理訊號擷取與電化學感測等。本論文提出一應用於尿液檢測之直接電流感測二階三角積分調變器的高能效電化學讀取電路，主要為建構出前端電化學檢測所需之恆電位儀讀取電路，其特點在於所提出之電流感測三角積分調變器可直接與客製化開發之電化學感測器(ABTS-CNT)連結，且無需使用任何前置轉阻放大器便可直接量化於感測器所產生之氧化還原電流訊號，以達到簡化電路、改善動態範圍以及提高電流使用效率之特點。在整體架構上主要是利用額外的電容/電阻串聯電容作為第一級電流積分器，讓輸入氧化還原電流對此電容先進行充放電，再利用雙環形振盪器電路具有的先天一階雜訊整型能力，作為第二級相位積分器來達到二階雜訊整型的效果。此外，因所設計之電流積分器的轉移函式係數與輸入電流規格大小具有高度相關性，故此架構亦具備高度的可重構性，可作為一高能效、寬動態範圍且高度數位化之前端電流讀取電路，適合應用於尿液微白蛋白/肌酸酐比值的電化學檢測當中。

With the development of internet of things (IoT), studies on portable device and edge computing have become popular, and a low-power high-performance sensor readout has also attracted public attention throughout the years, such as biomedical signal acquisition and electrochemistry acquisition. This dissertation presents a power-efficient electrochemical readout ASIC with a direct current-sensing VCO-based 2nd-order CTDSM for the urine detection. The ASIC mainly includes a potentiostat with a current-sensing CTDSM, a hybrid-R DAC and a class-AB output buffer, which can be integrated with the customized dual-channel ABTS-CNT screen-printed carbon electrode (SPCE) for the urine albumin-to-creatinine ratio (UACR) detection. The proposed CTDSM can directly quantize the redox current from the ABTS-CNT biosensor without any pre-amplifier. Second-order noise shaping is simply achieved with an additional capacitor as a passive current integrator and a dual-VCO structure as a phase integrator. Measurement results show that the proposed current-sensing VCO-based 2nd-oder CTDSM can achieve a peak SNDR of 72 dB in 200 Hz while consuming 580 μW under 1.8 V supply, which leads to a power efficiency of 0.93. Experiment results have demonstrated that the proposed CTDSM can perfectly act as an amplifier-less current readout circuit in the proposed electrochemical urine detection system with the customized ABTS-CNT SPCE for sensor applications. Besides, also a modified architecture with the proportional-integral (PI) integrator and the programmable wide-dynamic-range IDAC has been proposed to further improve the performance of CTDSM.

[1] World Health Organization, “Cardiovascular diseases (CVDs),”. Accessed: May 18, 2020. [Online]. Available: https://www.who.int/en/news-room/fact-sheets/detail/cardiovascular-diseases-(cvds).
[2] K. Matsushita, J. Coresh, Y. Sang, J. Chalmers, C. Fox, E. Guallar, et al., “Estimated glomerular filtration rate and albuminuria for prediction of cardiovascular outcomes: a collaborative meta-analysis of individual participant data,” Lancet Diabetes & Endocrinology, vol. 3, no.7, pp. 514-525, July 2015.
[3] U. Lad, S. Khokhar and G. M. Kale, “Electrochemical Creatinine Biosensors,” Anal. Chem, 2008, 80, 21, 7910-7917.
[4] D. F. Putnam, “Composition and concentrative properties of human urine,” NASA Contractor Reports, 1971, NASA-CR-1802.
[5] R. T. Lagua and V. S. Claudio, “Nutrition and Diet Therapy Reference Dictionary,” 4 ed. Springer Netherlands, 1996, p. 491.
[6] H. J. Lambers Heerspink et al., “Albuminuria Assessed From First- Morning-Void Urine Samples Versus 24-Hour Urine Collections as a Predictor of Cardiovascular Morbidity and Mortality,” American Journal of Epidemiology, vol. 168, no. 8, pp. 897-905, 2008.
[7] A. Sun, A. G. Venkatesh, and D. A. Hall, “A Multi-Technique Reconfigurable Electrochemical Biosensor: Enabling Personal Health Monitoring in Mobile Devices,” IEEE Trans. Biomed. Circuits Syst., vol. 10, no. 5, pp. 945-954, Oct. 2016.
[8] B. Nasri et al., “Hybrid CMOS-Graphene Sensor Array for Subsecond Dopamine Detection,” IEEE Trans. Biomed. Circuits Syst., vol. 11, no. 6, pp. 1192-1203, Dec. 2017.
[9] F. Stradolini et al., “An IoT Solution for Online Monitoring of Anesthetics in Human Serum Based on an Integrated Fluidic Bioelectronic System,” IEEE Trans. Biomed. Circuits Syst., vol. 12, no. 5, pp. 1056-1064, Oct. 2018.
[10] D. -S. Ciou, P. -H. Wu, Y. -C. Huang, M. -C. Yang, S. -Y. Lee, and C. -Y. Lin, “Colorimetric and amperometric detection of urine creatinine based on the ABTS radical cation modified electrode,” Sensors and Actuators B: Chemical, vol. 314, pp.128034, July 2020.
[11] C. -C. Tu, Y. -K. Wang, and T. -H. Lin, “A Low-Noise Area-Efficient Chopped VCO-Based CTDSM for Sensor Applications in 40-nm CMOS,” IEEE J. Solid-State Circuits, vol. 52, no. 10, pp. 2523-2532, Oct. 2017.
[12] M. M. Ahmadi and G. A. Jullien, “A Wireless-Implantable Microsystem for Continuous Blood Glucose Monitoring,” IEEE Trans. Biomed. Circuits Syst., vol. 3, no. 3, pp. 169-180, June 2009.
[13] S. Abdollahvand, N. Paulino, L. Gomes and J. Goes, “A current-mode VCO-based amplifier-less 2nd-order ΔΣ modulator with over 85dB SNDR,” IEEE International Symposium on Circuits and Systems (ISCAS), Lisbon, Portugal, 2015, pp. 2037-2040.
[14] J. -H. Tsai, Y. -C. Chen, and Y. -T. Liao, “A Power-efficient Bidirectional Potentiostat-based Readout IC for Wide-range Electrochemical Sensing,” IEEE International Symposium on Circuits and Systems (ISCAS), Florence, Italy, 2018, pp. 1-5.
[15] S. -Y. Lee, P. -W. Huang, J. -R. Chiou, C. Tsou, Y. -Y. Liao, and J. -Y. Chen, “Electrocardiogram and Phonocardiogram Monitoring System for Cardiac Auscultation,” IEEE Trans. Biomed. Circuits Syst., vol. 13, no. 6, pp. 1471-1482, Dec. 2019.
[16] A. D. Krahn et al., “Use of an extended monitoring strategy in patients with problematic syncope,” Circulation, vol. 99, no. 3, pp. 406-410, Jan. 1999.
[17] T. Furukawa et al., “Additional diagnostic value of very prolonged observation by implantable loop recorder in patients with unexplained syncope,” J. Cardiovasc. Electrophysiol., vol. 23, pp. 67-71, Jan. 2012.
[18] Analog Device, AD8232, Single-Lead, Heart Rate Monitor Front End.
[19] J. Xu et al., “A wearable 8-channel active-electrode EEG/ETI acquisition system for body area networks,” IEEE J. Solid-State Circuits, vol. 49, no. 9, pp. 2005-2016, Sep. 2014.
[20] C. C. Enz and G. C. Temes, “Circuit techniques for reducing the effects of op-amp imperfections: Autozeroing, correlated double sampling, and chopper stabilization,” in Proceedings of the IEEE, vol. 84, no. 11, pp. 1854-1614, Nov. 1996.
[21] S. -Y. Lee et al., “Low-power wireless ECG acquisition and classification system for body sensor networks,” IEEE J. Biomed. Health Informat., vol. 19, no. 1, pp. 236-246, Jan. 2015.
[22] K. Chandrashekar and B. Bakkaloglu, “A 10 b 50MS/s opamp-sharing pipeline A/D with current-reuse OTAs,” IEEE Trans. Very Large Scale Integration (VLSI) Syst., vol. 19, no. 9, pp. 1610-1616, Sep. 2011.
[23] D. Kanemoto, T. Ido, and K. Taniguchi, “A novel third order delta sigma modulator with one opamp shared among three integrator stages,” IEICE Electron. Express, vol. 5, no. 24, pp. 1088-1092, 2008.
[24] S. -Y. Lee, P. -H. Su, K. -L. Huang, Y. -W. Hung, and J. -Y. Chen, “High-pass sigma–delta modulator with techniques of operational amplifier sharing and programmable feedforward coefficients for ECG signal acquisition,” IEEE Trans. Biomed. Circuits Syst., vol. 15, no. 3, pp. 443-453, June 2021.
[25] K. Lee, J. Chae, M. Aniya, K. Hamashita, K. Takasuka, S. Takeuchi, and G. C. Temes, “A noise-coupled time-interleaved ΔΣ ADC with 4.2 MHz Bandwidth, -98 dB THD and 79 dB SNDR,” IEEE J. Solid-State Circuits, Vol. 43, No. 12, pp. 2601-2612, Dec. 2008.
[26] R. Zanbaghi, T. S. Fiez, and G. Temes, “A new zero-optimization scheme for noise-coupled ΣΔ ADCs,” IEEE Int. Symposium on Circuits and Systems (ISCAS), May 2010, pp.2163-2166.
[27] Y. H. Leow, H. Tang, Z. C. Sun, and L. Siek, “A 1 V 103 dB 3rd-order audio continuous-time delta-sigma ADC with enhanced noise shaping in 65 nm CMOS,” IEEE J. Solid-State Circuits, vol. 51, no. 11, pp. 2625-2638, Nov. 2016.
[28] P. Malcovati, S. Brigati, F. Franncesconi, F. Maloberti, and A. Baschirotto, “Behavioral modeling of switched-capacitor sigma-delta modulators,” IEEE Trans. Circuits Syst. I, Fundam. Theory Appl., vol.50, no. 3, pp. 352-364, Mar. 2003.
[29] R. Schreier. (Feb. 2020). Delta Sigma Toolbox MathWorks. [Online]. Available: https://www.mathworks.com/matlabcentral/fileexchange/19-delta-sigma-toolbox
[30] B. Wicht, T. Nirschl, and D. Schmitt-Landsiedel, “Yield and speed optimization of a latch-type voltage sense amplifier,” IEEE J. Solid-State Circuits, vol. 39, no. 7, pp. 1148-1158, July 2004.
[31] S. Song et al., “A 430 nW 64 nV/√H z current-reuse telescopic amplifier for neural recording applications,” IEEE Biomed. Circuits Syst. Conf. (BioCAS), Oct./Nov. 2013, pp. 322-325.
[32] A. Noman, M. Dessouky, and K. Sharaf, “A dual phase SC CMFB circuit for double sampling modulators,” IEEE 2003 46th Midwest Symposium on Circuits and Systems, Dec. 2003, pp. 287-290.
[33] K. Kundert, “Simulating switched-capacitors filter with SpectreRF,” The Designer’s Guide Community, Jul. 2006 [Online]. Available: http://www.designers-guide.org/analysis/sc-filters.pdf.
[34] I. -J. Chao, B. -D. Liu, S. -J. Chang, C. -Y. Huang, and H. -W. Ting, “Analyses of Splittable Amplifier Technique and Cancellation of Memory Effect for Opamp Sharing,” IEEE Trans. Very Large Scale Integr. (VLSI) Syst., vol. 25, no. 2, pp. 621-634, Feb. 2017.
[35] A. F. Yeknami, F. Qazi, and A. Alvandpour, “Low-power DT ΔΣ modulators using SC passive filters in 65 nm CMOS,” IEEE Trans. Circuits Syst. I, vol. 61, no. 2, pp. 358-370, Feb. 2014.
[36] F. Qazi and J. J. Da˛browski, “Passive SC sigma delta modulators revisited: Analysis and design study,” IEEE J. Emerg. Sel. Topics Circuits Syst., vol. 5, no. 4, pp. 624-637, Dec. 2015.
[37] L. Xu, B. Gönen, Q. Fan, J. H. Huijsing, and K. A. A. Makinwa, “A 110 dB SNR ADC with ±30V input common-mode range and 8μV offset for current sensing applications,” IEEE Int. Solid-State Circuits Conf. (ISSCC) Dig. Tech. Papers, Feb. 2015, pp. 1-3.
[38] S. Rout and W. Serdijn, “High-pass ∆∑ converter design using a state-space approach and its application to cardiac signal acquisition,” IEEE Trans. Biomed. Circuits Syst., vol. 12, no. 3, pp.483-494, Jun. 2018.
[39] J. Bang, H. Jeon, M. Je, and G. Cho, “6.5μW 92.3dB-DR biopotential recording front-end with 360mVpp linear input range,” IEEE Symposium on VLSI Circuits, Honolulu, 2018, pp. 239-240.
[40] H. Jeon, J. S. Bang, Y. Jung, I. Choi, and M. Je, “A high DR, DC coupled, time-based neural-recording IC with degeneration R-DAC for bidirectional neural interface,” IEEE J. Solid-State Circuits, vol. 54, no. 10, pp. 2658-2670, Oct. 2019.
[41] M. Reza Pazhouhandeh, M. Chang, T. A. Valiante, and R. Genov, “Track-and-zoom neural analog-to-digital converter with blind stimulation artifact rejection,” IEEE J. Solid-State Circuits, vol. 55, no. 7, pp. 1984-1997, Jul. 2020.
[42] A. Boni, L. Giuffredi, G. Pietrini, M. Ronchi, and M. Caselli, “A low-power sigma-delta modulator for healthcare and medical diagnostic applications,” IEEE Trans. Circuits Syst. I, vol. 69, no. 1, pp. 207-219, Jan. 2022.
[43] 邱嘉仁, 應用於心臟聽診之心電及心音訊號同步監控系統, 國立成功大學電機工程學系碩士論文, 2019.
[44] K. Lee, Y. Yoon, and N. Sun, “A Scaling-Friendly Low-Power Small-Area ΔΣ ADC With VCO-Based Integrator and Intrinsic Mismatch Shaping Capability,” IEEE J. Emerg. Sel. Topics Circuits Syst., vol. 5, no. 4, pp. 561-573, Dec. 2015.
[45] S. Li, A. Mukherjee, and N. Sun, “A 174.3-dB FoM VCO-Based CT ΔΣ Modulator With a Fully-Digital Phase Extended Quantizer and Tri-Level Resistor DAC in 130-nm CMOS,” IEEE J. Solid-State Circuits, vol. 52, no. 7, pp. 1940-1952, July 2017.
[46] G. G. E. Gielen, L. Hernandez, and P. Rombouts, “Time-Encoding Analog-to-Digital Converters: Bridging the Analog Gap to Advanced Digital CMOS-Part 1: Basic Principles,” IEEE Solid-State Circuits Magazine, vol. 12, no. 2, pp. 47-55, Spring 2020.
[47] G. G. E. Gielen, L. Hernandez, and P. Rombouts, “Time-Encoding Analog-to-Digital Converters: Bridging the Analog Gap to Advanced Digital CMOS-Part 2: Architectures and Circuits,” IEEE Solid-State Circuits Magazine, vol. 12, no. 3, pp. 18-27, Summer 2020.
[48] W. Jiang, V. Hokhikyan, H. Chandrakumar, V. Karkare, and D. Marković, “A ±50-mV Linear-Input-Range VCO-Based Neural-Recording Front-End With Digital Nonlinearity Correction,” IEEE J. Solid-State Circuits, vol. 52, no. 1, pp. 173-184, Jan. 2017.
[49] Geerts Y, Steyaert M, Sansen W. Design of multibit delta sigma A/D converters. New York: Kluwer Academic Publisher; 2002.
[50] H. Li, C. S. Boling, and A. J. Mason, “CMOS amperometric ADC With high sensitivity, dynamic range and power efficiency for air quality monitoring,” IEEE Trans. Biomed. Circuits Syst., vol. 10, no. 4, pp. 817–827, Aug. 2016.
[51] P. Prabha et al., “A Highly Digital VCO-Based ADC Architecture for Current Sensing Applications,” IEEE J. Solid-State Circuits, vol. 50, no. 8, pp. 1785-1795, Aug. 2015.
[52] S. S. Ghoreishizadeh, I. Taurino, G. De Micheli, S. Carrara, and P. Georgiou, “A Differential Electrochemical Readout ASIC With Heterogeneous Integration of Bio-Nano Sensors for Amperometric Sensing,” IEEE Trans. Biomed. Circuits Syst., vol. 11, no. 5, pp. 1148-1159, Oct. 2017.
[53] H. Son et al., “A Low-Power Wide Dynamic-Range Current Readout Circuit for Ion-Sensitive FET Sensors,” IEEE Trans. Biomed. Circuits Syst., vol. 11, no. 3, pp. 523-533, June 2017.
[54] Y. -C. Chen, S. -Y. Lu, and Y. -T. Liao, “A Microwatt Dual-Mode Electrochemical Sensing Current Readout With Current-Reducer Ramp Waveform Generation,” IEEE Trans. Biomed. Circuits Syst., vol. 13, no. 6, pp. 1163-1174, Dec. 2019.
[55] C. Lee et al., “A 6.5-μW 10-kHz BW 80.4-dB SNDR Gm-C-Based CT ∆∑ Modulator With a Feedback-Assisted Gm Linearization for Artifact-Tolerant Neural Recording,” IEEE J. Solid-State Circuits, vol. 55, no. 11, pp. 2889-2901, Nov. 2020.
[56] A. Mohamed, L. Baumgärtner, J. Zhao, D. Djekic, and J. Anders, “A current-mode Σ△ modulator with FIR feedback and DC servo loop for an improved dynamic range,” IEEE International Symposium on Circuits and Systems (ISCAS), 2022, pp. 1239-1243.
[57] Y. -T. Hsieh, S. -S. Chang, H. -Y. Lee, J. -Y. Chen, and S. -Y. Lee, “A VCO-Based 2nd-Order Continuous Time Sigma-Delta Modulator for Current-Sensing Systems,” IEEE International Symposium on Circuits and Systems (ISCAS), 2022, pp. 2576-2579.
[58] H. -Y. Lee, P. -W. Huang, D. -S. Ciou, Z. -X. Liao, and S. -Y. Lee, “A Power-Efficient Current Readout Circuit with VCO-Based 2nd-Order CT Δ∑ ADC for Electrochemistry Acquisition,” IEEE Asian Solid-State Circuits Conf. (A-SSCC), Hiroshima, Japan, 2020, pp. 1-2.
[59] S. -Y. Lee, H. -Y. Lee, D. -S. Ciou, Z. -X. Liao, P. -W. Huang, Y. -T. Hsieh, Y. -C. Wei, C. -Y. Lin, M. -D. Shieh, and J. -Y Chen, “A Portable Wireless Urine Detection System with Power-Efficient Electrochemical Readout ASIC and ABTS-CNT Biosensor for UACR Detection,” IEEE Trans. Biomed. Circuits Syst., vol. 15, no. 3, pp. 537-548, June 2021.
[60] Y. Jung et al., “A Wide-Dynamic-Range Neural-Recording IC With Automatic-Gain-Controlled AFE and CT Dynamic-Zoom ΔΣ ADC for Saturation-Free Closed-Loop Neural Interfaces,” IEEE J. Solid-State Circuits, vol. 57, no. 10, pp. 3071-3082, Oct. 2022.
[61] N. Qiao and G. Indiveri, “An auto-scaling wide dynamic range current to frequency converter for real-time monitoring of signals in neuromorphic systems,” IEEE Biomedical Circuits and Systems Conference (BioCAS), 2016, pp. 160-163.
[62] R. K. Pandey and P. C. . -P. Chao, “An Adaptive Analog Front End for a Flexible PPG Sensor Patch with Self-Determined Motion Related DC Drift Removal,” IEEE International Symposium on Circuits and Systems (ISCAS), 2021, pp. 1-5.