A 47.5nJ Resistor-to-Digital Converter for Detecting BTEX with 0.06ppb-Resolution

This paper describes an energy-efficient resistor-to-digital converter (RDC) for detecting benzene, toluene, ethylbenzene and xylene (BTEX). The sensor’s selectivity is adjusted by the different heat levels, thereby detecting the BTEX with a single-R sensor. The sensor is directly digitized by an energy-efficient RDC based on a continuous-time delta-sigma ADC. The proposed RDC achieves a better energy-efficiency by processing the signal in current domain. The prototype chip implemented in a 0.11-µm CMOS consumes only 95µW from a 1.5-V supply. It achieves a resistance resolution of 863mΩ with a 0.5-ms measurement time. This corresponds to a gas resolution of 0.06ppb and an energy per measurement of 47.5nJ. This work is fully verified through the BTEX measurements.