A Sub-/22W Embedded CMOS Temperature Sensor for RFID Food Monitoring Application Man Kay Law , Student Member , IEEE

Abstract

An ultra-low power embedded CMOS temperature sensor based on serially connected subthreshold MOS opera- tion is implemented in a 0.18 m CMOS process for passive RFID food monitoring applications. Employing serially con- nected subthreshold MOS as sensing element enables reduced minimum supply voltage for further power reduction, which is of utmost importance in passive RFID applications. Both proportional-to-absolute-temperature (PTAT) and complimen- tary-to-absolute-temperature (CTAT) signals can be obtained through proper transistor sizing. With the sensor core working under 0.5 V and digital interfacing under 1 V , the sensor dissipates a measured total power of 119 nW at 333 samples/s and achieves an inaccuracy of /431/ 0.8 Cf r o m 10 Ct o3 0 C after calibra- tion. The sensor is embedded inside the fabricated passive UHF RFID tag. Measurement of the sensor performance at the system level is also carried out, illustrating proper sensing operation for passive RFID applications.