A Low Power, Frequency-to-Digital Converter CMOS Based Temperature Sensor in 65 nm Process

A low power all CMOS based smart temperature sensor is introduced without using any bandgap reference or any current/voltage analog-to-digital converter. With the intention of low cost, power and area consumption, the proposed temperature sensor operates in sub-threshold region generating a temperature dependent frequency from the proportional to absolute temperature current. A digital output is obtained from the temperature dependent frequency by using a 12-bit asynchronous counter. A temperature insensitive ring oscillator is designed used a reference clock signal in counter. The temperature sensor is implemented using 65 nm CMOS standard process and its operation is validated through post-layout simulation results, at a power supply of (0.5-1)-V. The sensor has an uncalibrated accuracy of +2.4/-2.1 degrees C for (-55 to 125) degrees C and a resolution of 0.28 degrees C for the same range. The power and area consumed by the sensor is 1.55 mu W and 0.024 mm(2) respectively.