A Passive RFID Temperature Sensor With 0.16 °C Resolution, +0.42 °C/ -0.83 °C Inaccuracy and 0.234 nJ/Conversion

This paper presents an ultra-low power RFID with an embedded CMOS temperature sensor. The thermometry working flow of the Query01-Query00-Ack sequence is introduced, which is compatible with the EPC GEN-2 standard. A 2k-bits multi-time programmable (MTP) non-volatile memory (NVM) array with standard CMOS process is used to store tag information, tag-identification (TID), electronic product code (EPC), initialization parameter and temperature sensor (TS) data. The proposed rectifier can achieve a wide power dynamic range (PDR) of 21.5 dB with peak power conversion efficiency (PCE) of 65%@-15 dBm under a 100kΩ load. A protection mechanism for reliable reading and writing is presented to ensure proper tag initialization and avoid the ghost tag phenomenon. Time domain digital quantization is adopted to convert the signal that period varies with temperature into a digital signal for low power consumption. The temperature sensor achieves a resolution of 0.16°C and inaccuracy of +0.42/-0.83 °C after one point calibration at 0 °C in the temperature range from -20 °C to 30 °C. When the temperature sensor is powered at 1 V, it can achieve 0.234 nJ of energy per conversion in a conversion time of 1.8ms. The passive RFID temperature sensor occupies an area of 0.5579 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in 0.13um CMOS process. At the frequency of ~910 MHz, measured tag sensitivity can reach -22 dBm and the 3 dB bandwidth is 51.5 MHz.