This paper describes a voltage controlled oscillator (VCO) based temperature sensor. The VCOs are composed of complementary metal-oxide-semiconductor (CMOS) thyristor with the advantage of low power consumption. The period of the VCO is temperature dependent and is function of the transistors' threshold voltage and bias current. To obtain linear temperature characteristics, this paper constructed the period ratio between two different-type VCOs. The period ratio is independent of the temperature characteristics from current source, which makes the bias current generator simplified. The temperature sensor was designed in 130 nm CMOS process and it occupies an active area of 0.06 mm2. Based on the post-layout simulation results, after a first-order fit, the sensor achieves an inaccuracy of +0.37/-0.32 °C from 0 °C to 80 °C, while the average power consumption of the sensor at room temperature is 156 nW.
Keywords: CMOS thyristor; VCO; temperature sensor.