Ultra-Low-Power Interface Chip for Autonomous Capacitive Sensor Systems

Traditionally, most of the sensor interfaces must be tailored towards a specific application. This approach results in a high recurrent design cost and time to market. On the other hand, generic sensor interface design reduces the costs and offers a handy solution for multisensor applications. This paper presents a generic sensor interface chip (GSIC), which can read out a broad range of capacitive sensors. It contains capacitance-to-voltage converters, a switched-capacitor amplifier, an analog-to-digital converter, oscillators, clock generation circuits and a reference circuit. The system combines a very low-power design with a smart energy management, which adapts the current consumption according to the accuracy and speed requirements of the application. The GSIC is used in a pressure and an acceleration monitoring system. The pressure monitoring system achieves a current drain of 2.3 muA for a 10-Hz sample frequency and an 8-bit accuracy. In the acceleration monitoring system, we measured a current of 3.3 muA for a sample frequency of 10 Hz and an accuracy of 9 bits

[1]  Bernhard E. Boser,et al.  High-order electromechanical /spl Sigma//spl Delta/ modulation in micromachined inertial sensors , 2006, IEEE Transactions on Circuits and Systems I: Regular Papers.

[2]  N. Yazdi,et al.  Noise analysis and characterization of a sigma-delta capacitive microaccelerometer , 2006, IEEE Journal of Solid-State Circuits.

[3]  Bernhard E. Boser,et al.  High-order electromechanical ΣΔ modulation in micromachined inertial sensors. , 2006 .

[4]  Robert Puers,et al.  Design methods and algorithms for configurable capacitive sensor interfaces , 2005 .

[5]  Robert Puers,et al.  On the optimization of ultra low power front-end interfaces for capacitive sensors , 2005 .

[6]  B. Schaffer,et al.  Ultra low-power monolithically integrated, capacitive pressure sensor for tire pressure monitoring , 2004, Proceedings of IEEE Sensors, 2004..

[7]  N. Yazdi,et al.  A multi-step electromechanical /spl Sigma//spl Delta/ converter for micro-g capacitive accelerometers , 2003, 2003 IEEE International Solid-State Circuits Conference, 2003. Digest of Technical Papers. ISSCC..

[8]  Haluk Kulah.  Closed-loop electromechanical sigma-delta microgravity accelerometers. , 2003 .

[9]  Robert Puers,et al.  An autonomous bladder pressure monitoring system , 2002 .

[10]  Gerard C. M. Meijer,et al.  The temperature characteristics of bipolar transistors fabricated in CMOS technology , 2000 .

[11]  Khalil Najafi,et al.  A generic interface chip for capacitive sensors in low-power multi-parameter microsystems , 2000 .

[12]  Ramesh Harjani,et al.  An integrated low-voltage class AB CMOS OTA , 1999 .

[13]  W. Snelgrove,et al.  Clock jitter and quantizer metastability in continuous-time delta-sigma modulators , 1999 .

[14]  Bernhard E. Boser,et al.  A three-axis micromachined accelerometer with a CMOS position-sense interface and digital offset-trim electronics , 1999, IEEE J. Solid State Circuits.

[15]  Khalil Najafi,et al.  A generic multielement microsystem for portable wireless applications , 1998, Proc. IEEE.

[16]  Edgar Sanchez-Sinencio,et al.  Low-voltage class AB buffers with quiescent current control , 1998, IEEE J. Solid State Circuits.

[17]  Bo Wang,et al.  High-accuracy circuits for on-chip capacitive ratio testing and sensor readout , 1998, IEEE Trans. Instrum. Meas..

[18]  B. De Geeter,et al.  A wide temperature range micropower sensor interface circuit , 1996, ESSCIRC '96: Proceedings of the 22nd European Solid-State Circuits Conference.

[19]  F.M.L. Van der Goes,et al.  Low-Cost Smart Sensor Interfacing , 1996 .

[20]  Robert Puers,et al.  Capacitive sensors: When and how to use them☆ , 1993 .

[21]  F. O. Eynde,et al.  A high-speed CMOS comparator with 8-b resolution , 1992 .

[22]  Gabor C. Temes,et al.  A differential switched-capacitor amplifier , 1987 .

[23]  Robert W. Adams,et al.  Design and Implementation of an Audio 18-Bit Analog-to-Digital Converter Using Oversampling Techniques , 1986 .