期刊
IEEE JOURNAL OF SOLID-STATE CIRCUITS
卷 53, 期 11, 页码 3303-3313出版社
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/JSSC.2018.2866374
关键词
Carbon dioxide (CO2) sensor; CMOS compatible; delta-sigma modulator; phase-domain readout; resistive sensor; thermal conductivity (TC)
资金
- NXP Semiconductors, The Netherlands
- ams AG, The Netherlands
This paper presents a readout circuit for a carbon dioxide (CO2) 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 Delta Sigma 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 0.16-mu m CMOS technology, with an active area of 0.3 and 3.14 mm(2), 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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