A MEMS Oscillator and TDC-Based Temperature Sensing Architecture with Embedded Calibration

This paper presents a novel digital temperature sensing scheme operating over a wide range, integrating a high-temperature-coefficient-of-frequency (TCF) MEMS oscillator (205.65 ppm/°C) with a field-programmable gate array (FPGA)-based single-chain time-to-digital converter (TDC). The system employs an iterative compensation calibration method, utilizing data from -40°C to 80°C, to mitigate temperature drift. This calibration improves the TDC root mean square (rms) resolution from 34.88 ps to 23.55 ps. Testing shows that temperature-dependent errors in the uncalibrated system reach a maximum of 0.53°C (average 0.243°C), primarily due to oscillator drift and variations in the delay chain. After calibration, high accuracy is maintained between 20°C and 50°C, with errors consistently below 0.01°C. Performance degrades beyond 50°C due to increased phase noise, yet the maximum error at 70°C is only 0.06°C. The average error across the 20°C to 70°C range is significantly reduced to 0.019°C. The self-calibrating scheme eliminates external sensors, enabling compact and low-cost temperature sensing suitable for various harsh embedded environments.