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

Abstract

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.