A 1.2-V 8.3-nJ CMOS Humidity Sensor for RFID Applications

This paper presents a fully integrated CMOS humidity sensor for a smart RFID sensor platform. The sensing element is a CMOS-compatible capacitive humidity sensor, which consists of top-metal finger-structure electrodes covered by a humidity-sensitive polyimide layer. Its humidity-sensitive capacitan...

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Bibliographic Details
Published in:IEEE journal of solid-state circuits Vol. 48; no. 10; pp. 2469 - 2477
Main Authors: Zhichao Tan, Daamen, Roel, Humbert, Aurelie, Ponomarev, Youri V., Youngcheol Chae, Pertijs, Michiel A. P.
Format: Journal Article
Language:English
Published: New York, NY IEEE 01.10.2013
Institute of Electrical and Electronics Engineers
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
Amplifiers
Applied sciences
Capacitance
Capacitance-to-digital converter
capacitive-sensor interface
Capacitors
Circuit properties
CMOS
CMOS integrated circuits
current-starved cascoded inverter (CSCI)
delta-sigma modulator
Design. Technologies. Operation analysis. Testing
Electric, optical and optoelectronic circuits
Electronic circuits
Electronic equipment and fabrication. Passive components, printed wiring boards, connectics
Electronics
Exact sciences and technology
Humidity
humidity sensor
Integrated circuits
Inverters
Modulation
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Sensors
Signal convertors
Polyimide
Moisture sensor
Digital converter
Sigma-delta modulation
humidity sensor
delta-sigma modulator
Complementary MOS technology
Humidity
Electric power consumption
Minimum energy
Feedforward
Transconductance
capacitive-sensor interface
current-starved cascoded inverter (CSCI)
Inverter
Modulator
Operational amplifier
Capacitive transducer
Third order
Measurement sensor
Baseline
Capacitance-to-digital converter
Intelligent sensors
Capacitance
Low-power electronics
Capacitor
Radio frequency identification
ISSN:0018-9200, 1558-173X
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Summary:This paper presents a fully integrated CMOS humidity sensor for a smart RFID sensor platform. The sensing element is a CMOS-compatible capacitive humidity sensor, which consists of top-metal finger-structure electrodes covered by a humidity-sensitive polyimide layer. Its humidity-sensitive capacitance is digitized by an energy-efficient capacitance-to-digital converter (CDC) based on a third-order delta-sigma modulator. This CDC employs current-efficient operational transconductance amplifiers based on current-starved cascoded inverters, whose limited output swing is accommodated by employing a feedforward loop-filter topology. A programmable offset capacitor is included to remove the sensor's baseline capacitance and thus reduce the required dynamic range. To reduce offset errors due to charge injection of the switches, the entire system is auto-zeroed. The proposed humidity sensor has been realized in a 0.16- μm CMOS technology. Measurement results show that the CDC performs a 12.5-bit capacitance-to-digital conversion in a measurement time of 0.8 ms, while consuming only 8.6 μA from a 1.2-V supply. This corresponds to a state-of-the-art figure-of-merit of 1.4 pJ/conversion-step. Combined with the co-integrated humidity sensing element, it provides a resolution of 0.05% RH in the range from 30% RH to 100% RH while consuming only 8.3 nJ per measurement, which is an order-of-magnitude less energy than the state-of-the-art.
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ISSN:0018-9200
1558-173X
DOI:10.1109/JSSC.2013.2275661