An Energy-Efficient Miniaturized Intracranial Pressure Monitoring System

A miniaturized pressure-sensing microsystem targeting intracranial pressure monitoring is presented. The system takes full advantage of Invensense MEMS-CMOS process to heterogeneously integrate the sensor and interface. This integration type requires no fabrication postprocessing and results in sub-pF sensor-interface parasitic interconnection capacitance <inline-formula> <tex-math notation="LaTeX">$C_{p}$ </tex-math></inline-formula> which is an order of magnitude smaller than previously reported <inline-formula> <tex-math notation="LaTeX">$C_{p}\text{s}$ </tex-math></inline-formula>. Since energy efficiency is of main concern, the minimum energy consumption for maintaining a certain signal-to-noise ratio (SNR) is analytically calculated and compared for two energy-efficient sensor front ends, namely, the switched-capacitor (SC) capacitance-to-voltage converter (CVC) and the successive approximation register (SAR) capacitance-to-digital converter (CDC). The comparison reveals for small values of <inline-formula> <tex-math notation="LaTeX">$C_{p}$ </tex-math></inline-formula> and for low-to-moderate SNR, the SAR CDC outperforms the SC CVC in terms of power consumption. Heterogeneous integration of sensor and CMOS electronics results in only 720 fF of <inline-formula> <tex-math notation="LaTeX">$C_{p}$ </tex-math></inline-formula> which enables direct SAR capacitance-to-digital conversion. Correlated double sampling is also integrated into the proposed SAR switching scheme to combat 1/<inline-formula> <tex-math notation="LaTeX">$f$ </tex-math></inline-formula> noise and the input-referred offset voltage of the comparator. The entire pressure-sensing system measures <inline-formula> <tex-math notation="LaTeX">$2.2\times 2.6\times 0.4$ </tex-math></inline-formula> mm<sup>3</sup> in size, consumes 130 nW at 60-Hz sampling rate, and obtains 57-dB SNR with 0.2% sensor-electronics combined linearity over 520-mmHg pressure range.

[1]  Gerard C. M. Meijer,et al.  A novel low-cost capacitive-sensor interface , 1996 .

[2]  Boby George,et al.  Analysis of the Switched-Capacitor Dual-Slope Capacitance-to-Digital Converter , 2010, IEEE Transactions on Instrumentation and Measurement.

[3]  Simone Gambini,et al.  An energy-efficient heterogeneously-integrated capacitive pressure sensing system , 2015, 2015 IEEE Biomedical Circuits and Systems Conference (BioCAS).

[4]  M. Libicher,et al.  US measurement of the subarachnoid space in infants: normal values. , 1992, Radiology.

[5]  Kenzo Watanabe,et al.  A switched-capacitor interface for capacitive sensors with wide dynamic range , 1989 .

[6]  R. Jacob Baker,et al.  CMOS Circuit Design, Layout, and Simulation , 1997 .

[7]  Odette A. Harris,et al.  Guidelines for the Management of Severe Traumatic Brain Injury, Fourth Edition , 2016, Neurosurgery.

[8]  J. Ghajar,et al.  In Reply: Guidelines for the Management of Severe Traumatic Brain Injury: 2020 Update of the Decompressive Craniectomy Recommendations. , 2020, Neurosurgery.

[9]  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.

[10]  Alessandro Trifiletti,et al.  88-$\mu$ A 1-MHz Stray-Insensitive CMOS Current-Mode Interface IC for Differential Capacitive Sensors , 2014, IEEE Transactions on Circuits and Systems I: Regular Papers.

[11]  Xiujun Li,et al.  Elimination of shunting conductance effects in a low-cost capacitive-sensor interface , 2000, IEEE Trans. Instrum. Meas..

[12]  S. Nasiri,et al.  DEVELOPMENT OF HIGH-PERFORMANCE, HIGH-VOLUME CONSUMER MEMS GYROSCOPES , 2010 .

[13]  K.D. Wise,et al.  A high-performance silicon tactile imager based on a capacitive cell , 1985, IEEE Transactions on Electron Devices.

[14]  Catherine Dehollain,et al.  Design and Implementation of a 46-kS/s CMOS SC Dual-Mode Capacitive Sensor Interface With 50-dB SNR and 0.7% Nonlinearity , 2015, IEEE Sensors Journal.

[15]  Carlos H. Mastrangelo,et al.  Surface-micromachined capacitive differential pressure sensor with lithographically defined silicon diaphragm , 1996 .

[16]  Kenzo Watanabe,et al.  A switched-capacitor charge-balancing analog-to-digital converter and its application to capacitance measurement , 1987, IEEE Transactions on Instrumentation and Measurement.

[17]  Muhammad Arsalan,et al.  7.9 pJ/Step Energy-Efficient Multi-Slope 13-bit Capacitance-to-Digital Converter , 2014, IEEE Transactions on Circuits and Systems II: Express Briefs.

[18]  Boby George,et al.  Switched Capacitor Signal Conditioning for Differential Capacitive Sensors , 2007, IEEE Transactions on Instrumentation and Measurement.

[19]  Carlos H. Mastrangelo,et al.  Contamination-insensitive differential capacitive pressure sensors , 2000 .

[20]  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.

[21]  Xiujun Li,et al.  An accurate interface for capacitive sensors , 2002, IEEE Trans. Instrum. Meas..

[22]  Marilyn J. Cipolla,et al.  Control of Cerebral Blood Flow , 2009 .

[23]  Boby George,et al.  Switched capacitor triple slope capacitance to digital converter , 2006 .

[24]  Kenzo Watanabe,et al.  A Capacitive Pressure Sensor Interface Using , 1997 .

[25]  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.

[26]  Cheng-Ta Chiang,et al.  A Monolithic CMOS Autocompensated Sensor Transducer for Capacitive Measuring Systems , 2008, IEEE Transactions on Instrumentation and Measurement.

[27]  B. Wang,et al.  New high-precision circuits for on-chip capacitor ratio testing and sensor readout , 1998, ISCAS '98. Proceedings of the 1998 IEEE International Symposium on Circuits and Systems (Cat. No.98CH36187).

[28]  M. Yamada,et al.  A capacitive pressure sensor interface using oversampling /spl Delta/-/spl Sigma/ demodulation techniques , 1997 .

[29]  Nguyen Thanh Trung,et al.  A Submicrowatt Implantable Capacitive Sensor System for Biomedical Applications , 2015, IEEE Transactions on Circuits and Systems II: Express Briefs.

[30]  Gerard C. M. Meijer,et al.  A low-cost, smart capacitive position sensor , 1992 .

[31]  David Blaauw,et al.  12.6 A 160nW 63.9fJ/conversion-step capacitance-to-digital converter for ultra-low-power wireless sensor nodes , 2014, 2014 IEEE International Solid-State Circuits Conference Digest of Technical Papers (ISSCC).

[32]  B. Murmann.  Thermal Noise in Track-and-Hold Circuits: Analysis and Simulation Techniques , 2012, IEEE Solid-State Circuits Magazine.

[33]  Paolo Bruschi,et al.  A Low-Power Interface for Capacitive Sensors With PWM Output and Intrinsic Low Pass Characteristic , 2013, IEEE Transactions on Circuits and Systems I: Regular Papers.

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

[35]  Kenzo Watanabe,et al.  A switched-capacitor interface for capacitive pressure sensors , 1991, [1991] Conference Record. IEEE Instrumentation and Measurement Technology Conference.

[36]  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.

[37]  Andrzej Cichocki,et al.  A switched-capacitor interface for capacitive sensors based on relaxation oscillators , 1990 .

[38]  Pierluigi Nuzzo,et al.  Noise Analysis of Regenerative Comparators for Reconfigurable ADC Architectures , 2008, IEEE Transactions on Circuits and Systems I: Regular Papers.

[39]  Lei Wang,et al.  A Power-Efficient Capacitive Read-Out Circuit With Parasitic-Cancellation for MEMS Cochlea Sensors , 2016, IEEE Transactions on Biomedical Circuits and Systems.

[40]  D. Wenzel,et al.  Low power integrated pressure sensor system for medical applications , 1999 .

[41]  Gerard C. M. Meijer,et al.  A very accurate measurement system for multielectrode capacitive sensors , 1996 .

[42]  Kenzo Watanabe,et al.  A switched-capacitor interface for intelligent capacitive transducers , 1986, IEEE Transactions on Instrumentation and Measurement.

[43]  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.

[44]  R. Puers,et al.  Ultra-Low-Power Interface Chip for Autonomous Capacitive Sensor Systems , 2007, IEEE Transactions on Circuits and Systems I: Regular Papers.

[45]  J. Pickard,et al.  Monitoring and interpretation of intracranial pressure , 2004, Journal of Neurology, Neurosurgery & Psychiatry.