Supply sensitivity analysis for low-power time-domain temperature sensor in RFID application

摘要

In this paper the supply sensitivity of low-power time-domain temperature sensors in RFID sensor tags is analyzed. A common topology of recent published temperature sensors is proposed. Three time-domain temperature sensor topologies (“Inverted based topology”, “SC delay cell with two bias sources” and “SC delay cell with common bias source”) are modeled in this proposed common structure via Verilog A. A supply sensitivity analysis is performed for these three topologies. In the simulation the supply is swept first by DC supply voltage variation of ±100mV. The topology “SC delay cell with common bias source”, which is the most robust design among the three topologies, achieves only 0.0006°C/mV. This result is almost 50 times smaller than other two topologies in a same defined simulation condition. In a further AC analysis this topology shows a maximal AC supply sensitivity 0.55°C/mV over a frequency range from 10Hz to 1MHz. This supply sensitivity gives a specification of RFID power management block, that the power supply rejection (PSR) of low-dropout regulator (LDO) should be -52dB to achieve an accuracy of ±1°C under a realistic condition.