A Phase-Domain Readout Circuit for a CMOS-Compatible Hot-Wire CO₂ Sensor

Journal Article (2018)
Author(s)

Zeyu Cai (NXP Semiconductors, TU Delft - Electronic Instrumentation)

R. van Veldhoven (NXP Semiconductors)

Hilco Suy (Ams AG)

Ger de Graaf (TU Delft - Electronic Instrumentation)

Kofi Makinwa (TU Delft - Microelectronics)

Michiel A.P. Pertijs (TU Delft - Electronic Instrumentation)

Research Group
Electronic Instrumentation
Copyright
© 2018 Z. Cai, Robert van Veldhoven, Hilco Suy, G. de Graaf, K.A.A. Makinwa, M.A.P. Pertijs
DOI related publication
https://doi.org/10.1109/JSSC.2018.2866374
More Info
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Publication Year
2018
Language
English
Copyright
© 2018 Z. Cai, Robert van Veldhoven, Hilco Suy, G. de Graaf, K.A.A. Makinwa, M.A.P. Pertijs
Research Group
Electronic Instrumentation
Bibliographical Note
Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. @en
Issue number
11
Volume number
53
Pages (from-to)
3303-3313
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Abstract

This paper presents a readout circuit for a carbon dioxide (COࠢ) sensor that measures the CO₂-dependent thermal time constant of a hot-wire transducer. The readout circuit periodically heats up the transducer and uses a phase-domain Δ Σ modulator to digitize the phase shift of the resulting temperature transients. A single resistive transducer is used both as a heater and as a temperature sensor, thus greatly simplifying its fabrication. To extract the transducer's resistance, and hence its temperature, in the presence of large heating currents, a pair of transducers is configured as a differentially driven bridge. The transducers and the readout circuit have been implemented in a standard 0.16μm CMOS technology, with an active area of 0.3 and 3.14 mm², respectively. The sensor consumes 6.8 mW from a 1.8-V supply, of which 6.3 mW is dissipated in the transducers. A resolution of 94-ppm CO₂ is achieved in a 1.8-s measurement time, which corresponds to an energy consumption of 12 mJ per measurement, >10x less than prior CO₂ sensors in CMOS technology.

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