A primary-auxiliary temperature sensing scheme for multiple hotspots in system-on-a-chips

A primary-auxiliary temperature sensing scheme for system-on-a-chip application is proposed in this paper. Taking advantage of the high accuracy and linearity of the analog primary temperature sensors and low production cost of the digital auxiliary temperature sensors, this sensing scheme monitors multiple hotspots in a highly integrated system chip with small area and low power. A cost efficient calibration strategy based on the difference of calibration complexity and sensitivity to the MOSFET aging between the primary and auxiliary temperature sensors is also presented in this paper. Both the temperature sensor prototypes are designed and fabricated with a 90-nm CMOS process technology. The core area of the primary/auxiliary temperature sensors is 0.039/0.001 {\rm mm}^{2} , and consumed energy per conversion is 20.06/0.136 nJ/S with a 1 V supply voltage and 100-kS/s conversion rate. The performance of the temperature sensors and the accuracy improvement of the proposed calibration method are proved with the measurement results.