Design of an Integrated Low-Power Capacitive Sensor Readout Circuit

This book reports the development of an integrated
low-power readout circuit for a capacitive sensor
with 40 - 60 pF basic capacitance. The sensor is used
to detect screw loosening in an osteosynthesis
measurement system. To ensure detection of screw
loosening the readout circuit must be able to measure
capacitance changes of at least 0.25 pF. Several
readout techniques for capacitive sensors are
investigated and evaluated for this application.
Finally two types are developed and simulated, a
Wien-bridge oscillator and a switched capacitor (SC)
capacitance to voltage (C/V) converter. The
oscillator is simulated with Cadence in a 0.35 µm
triple-well, 4-metal, and double poly CMOS process
from austriamicrosystems. The Wien-bridge is adapted
for CMOS integration. Additionally, a SC
C/V-converter is developed and simulated in the same
process to compare the readout techniques. The target
audience for this book are electronic engineers,
students and people who are interested in working and
developing with simulation tools.

Autorentext
After an apprenticeship to an electronic technician, he achieved his vocational diploma by the constinuation education. From 2002 to 2006 he studied telecommunication engineering at the University of Applied Science in Offenburg (Germany). He is currently acting in the research and development of driver circuits for semiconductor lasers.

Klappentext
This book reports the development of an integrated low-power readout circuit for a capacitive sensor with 40 - 60 pF basic capacitance. The sensor is used to detect screw loosening in an osteosynthesis measurement system. To ensure detection of screw loosening the readout circuit must be able to measure capacitance changes of at least 0.25 pF. Several readout techniques for capacitive sensors are investigated and evaluated for this application. Finally two types are developed and simulated, a Wien-bridge oscillator and a switched capacitor (SC) capacitance to voltage (C/V) converter. The oscillator is simulated with Cadence in a 0.35 µm triple-well, 4-metal, and double poly CMOS process from austriamicrosystems. The Wien-bridge is adapted for CMOS integration. Additionally, a SC C/V-converter is developed and simulated in the same process to compare the readout techniques. The target audience for this book are electronic engineers, students and people who are interested in working and developing with simulation tools.