CMOS thermal sensing system with simplified circuits and high accuracy for biomedical application

A low-cost thermal sensor with sigma-delta ADC was realized in 0.25mum CMOS process. Simplify the circuitry with different technologies to improve the efficiency and reduce the error in the thermal sensor chip. Substrate npn transistors are used to sense the temperature and generate the ADC´s reference voltage. The ingenious application of sigma-delta ADCs can reduce the complexity of circuit, thereby reducing system cost, area and power consumption. Attach importance to the body temperature (37 plusmn 4 degC), from +33 degC to +42 degC, the inaccuracy is less than plusmn0.15 degC with one-point calibration after packaging. This paper proposes here to further develop this thermal sensor chip (including the calibration of the system) and to use this chip for biomedical application