Temperature-to-Frequency Converter With 1.47% Error Using Thermistor Linearity Calibration

Temperature variation is well known to be very critical for estimating other parameters, e.g., the state of charge and the state of health of batteries. A high-accuracy temperature to frequency converter with thermistor linear calibration based on the thermistor linearization circuit is designed and analyzed in this investigation, where a voltage-to-frequency converter (VFC) is added instead of an analog-to-digital converter. The proposed design converts the voltage into a digital signal (frequency output) to reduce design complexity as well as the cost of chip area. A detailed analysis, including the method using the thermistor linearization calibration circuit and VFC, is reported in this paper. The measurement results in a thermal chamber establish that the output frequency is 1.62 to 2.27 MHz, the maximum linearity error is ±0.5%, and the temperature error is ≤1.47% in the temperature range of 268.15 to 313.15 K.