Digital systems architecture to accommodate wide range resistance changes of metal-oxide sensors

A monolithic gas sensor array fabricated in industrial CMOS technology combined with post-CMOS micromachining is presented. The device comprises an array of three metal-oxide-coated micro-hotplates with integrated MOS transistor heaters and the needed driving and signal-conditioning circuitry. Three digital PID controllers enable individual temperature regulation for each hotplate. The operating temperature of the SnO₂ metal-oxide sensors may amount up to 350degC. A serial interface and the temperature control units have been implemented digitally. The mainly digital implementation offers the advantage to apply a power-saving mode and temperature modulation techniques to enhance the analyte discrimination capability.