Full passive RFID pressure sensor with a low power and low voltage time to digital interface

There is a strong motivation for the development of low-power RFID sensors tags. In this work, a full passive RFID pressure sensor tag is presented paying special attention to a time to digital converter based on nonius oscillators. The circuit has been designed using a 90nm CMOS standard process. Post-layout simulations show that the nonius converter allows the estimation of the input pulse width in the range from 34μs to 51μs with a LSB of 2ns and an effective resolution of 8.3 bits. It requires a maximum conversion time of 97.8μs with an average power consumption of 1.59μW from a 0.7V supply voltage. The comparison of these results with the state of the art showed that, according to the authors´ knowledge, the proposed sensor interface has the best characteristics in terms of minimum power consumption and supply voltage level. Therefore, it is a remarkable solution for passive RFID sensor applications.