Ultralow-Power Smart Temperature Sensor with Subthreshold CMOS Circuits

We proposed a smart temperature sensor LSI consisting of subthreshold CMOS circuits. The sensor was composed of a bias circuit, a PTAT current generator, an A/D converter, and a counter circuit. All of the circuits were designed so that MOSFETs in the circuits would operate in the subthreshold region to achieve ultralow power consumption. The PTAT current generator was the key component of the sensor and was constructed by using the characteristics of a MOSFET in the subthreshold region. Simulation with SPICE demonstrated that the circuit can be used as a smart temperature sensor with ultralow-power consumption of 6 muW or less.