Quasi-Digital CMOS Temperature Sensor for on-Chip Thermal Monitoring of Self-X Systems

Abstract:
This paper presents a simple and fully integrated small size CMOS temperature sensor with quasi digital output for onchip temperature monitoring. The proposed circuit converts the linear temperature-dependent current of the proportional to absolute temperature (PTAT) biasing circuit into a frequency signal by exciting a simple current-mode relaxation oscillator (RO). In order to reduce the circuit area, a current-mode comparator is used in the design of the RO. The postlayout simulations show that under the worst-case process corners and ±10% supply voltage variation, the temperature sensor has a maximum absolute nonlinearity error of 2:4 °C for the temperature range from -40 °C to +85 °C with a power figure of merit equal to 0:2 muW/kHz. The circuit occupies a layout area of 0:028 mm2. The circuit is designed using the XFAB 0:35 mm technology and Cadence Virtuoso tools for verification and physical implementation.