A 1 pF-to-10 nF Generic Capacitance-to-Digital Converter Using Zero-Crossing $\Delta\Sigma$ Modulation

Conventional capacitance-to-digital converters (CDCs) suffer limitations either on narrow capacitance range or low resolution for jitter-induced noise and high power consumption. In order to avoid these limitations, a 13-b 1 pF–10 nF generic CDC is presented. In the proposed CDC with the oversampled <inline-formula> <tex-math notation="LaTeX">$\Delta \Sigma $ </tex-math></inline-formula> modulation, the zero-crossing-based circuits (ZCBCs) are used to replace the operational transconductance amplifier to avoid feedback loop stability issues. However, the ZCBCs inevitably incur the non-idealities and thus, a novel calibration scheme is presented for efficient non-ideality-error cancellation. In addition, for the purpose of making the proposed CDC sufficiently intelligent to adapt to a wide capacitance-sensing range, an adaptive auto-range mechanism is proposed. The above three techniques complement each other and work as a whole leading to the proposed CDC with wide range, high resolution, high linearity, and low power consumption. A prototype fabricated using 0.18-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS technology is experimentally verified using a MEMS capacitive humidity sensor. The measurement results show that the CDC achieves a 13-b root-mean-square noise equivalent resolution with a 128-<inline-formula> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> conversion time and a 230 fJ/conversion-step figure of merit. The calibration scheme enhances the linearity from 7 to 11.4 b in the 1 pF–10 nF compatible capacitance range.

[1]  Hae-Seung Lee,et al.  A Zero-Crossing-Based 8-bit 200 MS/s Pipelined ADC , 2007, IEEE Journal of Solid-State Circuits.

[2]  David Blaauw,et al.  27.6 A 0.7pF-to-10nF fully digital capacitance-to-digital converter using iterative delay-chain discharge , 2015, 2015 IEEE International Solid-State Circuits Conference - (ISSCC) Digest of Technical Papers.

[3]  Hae-Seung Lee,et al.  Comparator-based switched-capacitor circuits for scaled CMOS technologies , 2006, 2006 IEEE International Solid State Circuits Conference - Digest of Technical Papers.

[4]  A. Baschirotto,et al.  A 828μW 1.8V 80dB dynamic-range readout interface for a MEMS capacitive microphone , 2008, ESSCIRC 2008 - 34th European Solid-State Circuits Conference.

[5]  A. Bakker,et al.  A CMOS nested-chopper instrumentation amplifier with 100-nV offset , 2000, IEEE Journal of Solid-State Circuits.

[6]  A. Matsuzawa,et al.  A 0.026mm2 capacitance-to-digital converter for biotelemetry applications using a charge redistribution technique , 2007, 2007 IEEE Asian Solid-State Circuits Conference.

[7]  R. Sabbaghi‐Nadooshan,et al.  Design and simulation of high sensitive capacitive pressure sensor with slotted diaphragm , 2012, 2012 International Conference on Biomedical Engineering (ICoBE).

[8]  Khaled N. Salama,et al.  A 33fJ/Step SAR Capacitance-to-Digital Converter Using a Chain of Inverter-Based Amplifiers , 2017, IEEE Transactions on Circuits and Systems I: Regular Papers.

[9]  Hae-Seung Lee,et al.  A 12b 50MS/s fully differential zero-crossing-based ADC without CMFB , 2009 .

[10]  José Gerardo V. da Rocha,et al.  Capacitive Sensor for Three-Axis Force Measurements and Its Readout Electronics , 2009, IEEE Transactions on Instrumentation and Measurement.

[11]  Tony T. Kim,et al.  A 1.2 V, 0.84 pJ/conv.-Step ultra-low power capacitance to digital converter for microphone based auscultation , 2017, 2017 IEEE Custom Integrated Circuits Conference (CICC).

[12]  Kong-Pang Pun,et al.  A High-Linearity Capacitance-to-Digital Converter Suppressing Charge Errors From Bottom-Plate Switches , 2014, IEEE Transactions on Circuits and Systems I: Regular Papers.

[13]  Youngcheol Chae,et al.  A 1.2-V 8.3-nJ CMOS Humidity Sensor for RFID Applications , 2013, IEEE Journal of Solid-State Circuits.

[14]  Wei Wu,et al.  A compact sensor readout circuit with combined temperature, capacitance and voltage sensing functionality , 2017, 2017 Symposium on VLSI Circuits.

[15]  Anthony Chan Carusone,et al.  A 1-1-1-1 MASH Delta-Sigma Modulator With Dynamic Comparator-Based OTAs , 2012, IEEE Journal of Solid-State Circuits.

[16]  Andreas Kaiser,et al.  Very low-voltage digital-audio ΔΣ modulator with 88-dB dynamic range using local switch bootstrapping , 2001, IEEE J. Solid State Circuits.

[17]  Saleh Heidary Shalmany,et al.  27.7 A 0.05mm2 1V capacitance-to-digital converter based on period modulation , 2015, 2015 IEEE International Solid-State Circuits Conference - (ISSCC) Digest of Technical Papers.

[18]  Kofi A. A. Makinwa,et al.  A capacitance-to-digital converter for displacement sensing with 17b resolution and 20μs conversion time , 2012, 2012 IEEE International Solid-State Circuits Conference.

[19]  Abdulaziz Alhoshany,et al.  A 45.8fJ/Step, energy-efficient, differential SAR capacitance-to-digital converter for capacitive pressure sensing , 2016 .

[20]  Georges G. E. Gielen,et al.  A fully-digital, 0.3V, 270 nW capacitive sensor interface without external references , 2011, 2011 Proceedings of the ESSCIRC (ESSCIRC).

[21]  Gerard C. M. Meijer,et al.  An Energy-Efficient 15-Bit Capacitive-Sensor Interface Based on Period Modulation , 2012, IEEE Journal of Solid-State Circuits.

[22]  L. Benini,et al.  CMOS DNA Sensor Array With Integrated A/D Conversion Based on Label-Free Capacitance Measurement , 2006, IEEE Journal of Solid-State Circuits.

[23]  Chao Chen,et al.  A 1V 14b self-timed zero-crossing-based incremental ΔΣ ADC , 2013, 2013 IEEE International Solid-State Circuits Conference Digest of Technical Papers.

[24]  Peter R. Kinget,et al.  Current Reference Pre-Charging Techniques for Low-Power Zero-Crossing Pipeline-SAR ADCs , 2014, IEEE Journal of Solid-State Circuits.

[25]  David Blaauw,et al.  A Dual-Slope Capacitance-to-Digital Converter Integrated in an Implantable Pressure-Sensing System , 2014, IEEE Journal of Solid-State Circuits.

[26]  Philippe Renaud,et al.  A Telemetric Pressure Sensor System for Biomedical Applications , 2008, IEEE Transactions on Biomedical Engineering.

[27]  Hiroki Matsumoto,et al.  A high-accuracy digital readout technique for humidity sensor , 2001, IEEE Trans. Instrum. Meas..

[28]  Gabor C. Temes,et al.  Circuit techniques for reducing the effects of op-amp imperfections: autozeroing, correlated double sampling, and chopper stabilization , 1996, Proc. IEEE.

[29]  R. Thewes,et al.  A fully electronic DNA sensor with 128 positions and in-pixel A/D conversion , 2004, IEEE Journal of Solid-State Circuits.

[30]  D.J. Young,et al.  Wireless Batteryless Implantable Blood Pressure Monitoring Microsystem for Small Laboratory Animals , 2010, IEEE Sensors Journal.

[31]  Boby George,et al.  A Direct Digital Readout Circuit for Impedance Sensors , 2015, IEEE Transactions on Instrumentation and Measurement.

[32]  David Blaauw,et al.  15.4b incremental sigma-delta capacitance-to-digital converter with zoom-in 9b asynchronous SAR , 2014, 2014 Symposium on VLSI Circuits Digest of Technical Papers.

[33]  Nan Sun,et al.  An Energy-Efficient Hybrid SAR-VCO $\Delta \Sigma $ Capacitance-to-Digital Converter in 40-nm CMOS , 2017, IEEE Journal of Solid-State Circuits.