A Low Power, Frequency-to-Digital Converter CMOS Based Temperature Sensor in 65 nm Process Mudasir Bashir (&) , Sreehari Rao Patri, and K. S. R. Krishna Prasad Department of Electronics and Communication Engineering, National Institute of Technology, Warangal, India mudasir.mir7@gmail.com Abstract. A low power all CMOS based smart temperature sensor is intro- duced without using any bandgap reference or any current/voltage analog- to-digital converter. With the intention of low cost, power and area consump- tion, the proposed temperature sensor operates in sub-threshold region gener- ating 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 tem- perature 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 °C for (–55 to 125) °C and a resolution of 0.28 °C for the same range. The power and area consumed by the sensor is 1.55 μW and 0.024 mm 2 respectively. Keywords: Calibration Á Counter Á Low power Á PTAT Á Temperature sensor Temperature insensitive ring oscillator 1 Introduction Due to the progression in pervasive computing, internet of things (IoTs) and the increase in demand of portable and miniature electronic devices, demand of low-cost, high performance temperature sensor is increased. The aggressive scaling techniques and increased transistor integration results in amplified junction temperature gradient. These junction temperature variations affect the lifetime, performance and reliability of the electronic device by increasing the leakage power, timing issues, gate delay, self-heating and the overall cost [1]. Temperature sensors have become an important element in every system on chip (SoC), especially the on-chip temperature sensors, mostly because of their compactness, low cost, high performance and low power consumption. The low power consumption helps in mitigating the self-heating issues of these sensors. The on-chip temperature sensors are mostly used for thermal compen- sation and power consumption control in SoCs. Different types of temperature sensors have been realized in CMOS technology. The conventional block diagram of sensor with its interface is shown in Fig. 1. © Springer Nature Singapore Pte Ltd. 2017 B. K. Kaushik et al. (Eds.): VDAT 2017, CCIS 711, pp. 657–666, 2017. https://doi.org/10.1007/978-981-10-7470-7_62