A Low-Power BJT-Based Temperature Sensor with Wide Range and High Resolution

This paper proposes a temperature sensor designed for wearable devices, featuring high energy efficiency and a wide temperature range. The dual clamps circuit and current subtractor are utilized to generate sensing currents with high sensitivity, thus enhancing the system’s resolution. The current-to-frequency converter (CFC) employs an Edge Detector (ED) to approximate the two-fold output, increasing resolution and reducing frequency errors caused by delay time. By subtracting the digital codes from two 12-bit counters, the circuit’s accuracy and resolution are further improved. The prototype sensor, implemented in a 180 nm process, achieves an inaccuracy of +0.62 °C/-0.78 °C (3σ) from -60 °C to 110 °C, with a resolution of 40 mK in a 2.2 ms conversion time, resulting in a resolution figure of merit (FoM) of 3.9 pJ•K<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. The total power consumption is only 1.12 μW.