A CMOS MEMS thermal sensor with high frequency output

This work presents the design and characterization of a CMOS-integrated thermal sensor that features a novel oscillator-based sensing interface to achieve a high thermoelectric sensitivity. The thirty pairs of thermocouples are made of n⁺/p⁺ polysilicon of a standard 0.18-mum CMOS to produce a large thermoelectric voltage. The produced thermoelectric voltage is used to control the bias current of a high-frequency oscillator circuit and causes a shift in the output frequency. Experimental result indicates the 544-MHz oscillator has a temperature sensitivity of 46.3 kHz/degC.