Title :
A 16-channel capacitance-to-period converter with offset compensation for sensor applications
Author :
Ramfos, Ioannis ; Chatzandroulis, Stavros
Author_Institution :
Inst. of Microelectron., NCSR “Demokritos”, Athens, Greece
Abstract :
An electronic system able to read out arrays of up to sixteen different capacitive type sensors is presented. The output signal of the readout is a square wave signal, with oscillation period linearly modulated by the respective sensor capacitance under measurement. Components such as charge/discharge current control unit, a multiplexing unit and a bandgap voltage reference are integrated on chip, to obtain a stable and linear readout system for multiple sensors of variable types and capacitance ranges. The ASIC was designed and fabricated in AMS 0.35 μm CMOS technology and was hosted on a PCB together with a supervising microcontroller, which is programmed to produce ratiometric measurements using reference capacitances to minimise parasitic effects. Finally, a USB interface undertakes the task of communicating the results to a personal computer. During characterization the system exhibited up to 0.89 μs/pF sensitivity.
Keywords :
CMOS integrated circuits; application specific integrated circuits; capacitive sensors; ASIC; CMOS technology; bandgap voltage reference; capacitance-to-period converter; capacitive sensors; charge-discharge current control unit; multiplexing unit; offset compensation; oscillation period; readout output signal; size 0.35 mum; square wave signal; Capacitance; bandgap reference; capacitive sensor readout; multisensor; offset compensation; relaxation oscillator;
Conference_Titel :
Electronics, Circuits, and Systems (ICECS), 2010 17th IEEE International Conference on
Conference_Location :
Athens
Print_ISBN :
978-1-4244-8155-2
DOI :
10.1109/ICECS.2010.5724638