An Ultra-Low-Power Read-Out Circuit for Interfacing Novel Gas Sensors Matrices

• Published in: IEEE sensors journal Vol. 22; no. 10; pp. 9521 - 9533
• Main Authors: Puyol, Rafael, Petre, Sylvain, Danlee, Yann, Walewyns, Thomas, Francis, Laurent A., Flandre, Denis
• Format: Journal Article
• Language: English
• Published: New York IEEE 15-05-2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Ammonia; Bias; Circuit design; Circuits; Conducting polymers; Electrodes; Gas detectors; Gas sensors; Graphene; Integrated circuits; Nanomaterials; Nitrogen dioxide; Optimization; Polymer matrix composites; Power consumption; relaxation oscillator; Resistance; resistive read-out; Selectivity; Sensor phenomena and characterization; sensor systems; Sensors; Signal to noise ratio; System on chip; Temperature sensors; Transfer functions
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2022.3165755

New gas sensing materials, like conductive polymers and nanomaterials-based composites, together with integrated circuit advancements have enabled a new paradigm in gas sensing where a matrix of different types of sensors is used to improve selectivity and sensitivity. In this paper we present a highly flexible read-out circuit for acquiring the dc resistance of the sensors in the matrix. It can measure values from 1 <inline-formula> <tex-math notation="LaTeX">\text{k}\Omega </tex-math></inline-formula> up to 33 <inline-formula> <tex-math notation="LaTeX">\text{M}\Omega </tex-math></inline-formula>, with a minimum SNR of 57 dB. It also offers a wide range of input configuration in terms of resistance and bias voltages to select the optimal bias point for each sensor and to accommodate a large range of sensor types. It achieves very low power consumption at a maximum current consumption of <inline-formula> <tex-math notation="LaTeX">194~\mu \text{A} </tex-math></inline-formula> and an energy per conversion ranging from 1.21 nJ up to 188 nJ thanks to the optimization of the frequency of operation. The circuit was fabricated in a 180 nm bulk CMOS process and a complete characterization of the circuit is presented including current consumption, signal-to-noise ratio, and transfer function. Finally, the circuit was tested in a real application for the measurement of NH 3 and NO 2 using two different types of sensors validating the design objectives and the capability of the read-out circuit for system-on-chip integrations.