A 13-bit Temperature Sensor with a ±1.45°C (3σ) Inaccuracy from -55°C to 125°C

This paper introduces a bipolar junction transistor (BJT)-based CMOS temperature-to-digital converter (TDC) that demonstrates an accuracy of ±1.45°C (3σ) within a temperature range of -55°C to 125°C, achieved without the need for calibration. This result is attributed to the implementation of a second-order curvature compensation technique, which utilizes a switched capacitor integral circuit within the bandgap reference circuit. This approach effectively mitigates higher-order reference voltage errors, enhancing overall precision. Additionally, the paper incorporates dynamic element matching (DEM) and auto-zeroing techniques, applied in successive amplification stages, to minimize errors originating from current mirror mismatches and operational amplifier offset voltages, respectively. The described BJT-based sensor features a 13-bit successive-approximationregister analog-to-digital converter (SAR ADC), comprising a 5-bit capacitive array and an 8-bit resistor-capacitor hybrid array, designed to monitor and digitally record temperature data. The proposed design operates within a supply voltage range of 2.7V to 5.5V and is realized using a 0.6 μm BJT process, ultimately achieving a resolution of 29.7 mK.