Design and Simulation of a Wide Temperature Range Frequency-to-Data Converter Based on Threshold Voltage Dependent Thermal Sensor

This paper reports the design and simulation of an integrated CMOS threshold voltage dependent thermal sensor with a 10-bit frequency-to-data converter to generate the required temperature binary code. The thermal sensor makes use of the dedicated MOS transistors on CMOS process to build two ring oscillator structures, one is PMOS-enabled while the other is NMOS-enabled. The NMOS-enabled suffers a threshold voltage drop while passing the power supply rail. This leads to a lower oscillation frequency of the NMOS-enabled ring oscillator compared to that of PMOS-enabled ring oscillator. The division of the two oscillation frequencies is found to be a good inversely fit of temperature. The linearity error is confined to +/-3°C over a temperature range of -40°C to 130°C and supply voltage of 5V ± 5%, with calibration performed over three temperature ranges, i.e. -40 to 25°C, 26 - 98°C, and 99 - 130°C.