Development of temperature sensor for UHF implantable RFID chips
In this work,a temperature sensor designed for UHF implantable RFID chips is implemented using a 0.18 μm process.The sensor employs MOS transistors as the temperature-sensing elements,with the core design based on a low-power temperature sensing circuit using subthreshold MOS transistors.The sensor utilizes Proportional To Absolute Temperature(PTAT)and Complementary To Absolute Temperature(CTAT)voltage delay generators to form a pulse width generation circuit,which produces pulse width signals that are quantified by a Time-to-Digital Converter(TDC).The core circuit layout area is 298 μm ×261 μm,with a temperature meas-urement range of 35～45℃.Tape-out testing results indicated that,after two-point calibration,the maximum temperature measure-ment error across three chips was±0.4 ℃,with a maximum error of±0.2 ℃ in critical temperature ranges.The measured power consumption was 623 nW.Based on the tape-out results,the current chip's limitations were identified,and directions for future chip structure iterations were proposed.
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