A Fully Integrated Single-BJT-Based Temperature-to-Digital Converter Achieving ±0.23 °C (3σ) Over 2.0-5.5 V for Duty-Cycled Operation

초록

This article presents a fully integrated temperatureto-digital converter (TDC) fabricated in a 0.18 & micro;m CMOS process, employing a single bipolar junction transistor (BJT). The proposed front-end sequentially biases a single BJT at two current levels to generate a triangle VBE, thereby eliminating the need for matched BJT pairs and improving reproducibility with a one-point calibration. All critical analog and digital blocks-including the sensing front-end, an incremental deltasigma analog-to-digital converter, power management units (PMUs), clock generators, e-fuse memory, digital processing logic, and an (IC)-C-2 interface-are fully integrated on-chip to enable compact and standalone operation. After one-point calibration at 30 degrees C, the TDC achieves an inaccuracy of +/- 0.23 C-degrees (3 sigma) over a -40 C-degrees to 125 C-degrees temperature range. At a conversion time of 7.68 ms, it achieves a 6.71 mK rms resolution, corresponding to a system-level resolution figure of merit (FoM) of 75.3 pJ & centerdot; K-2 . For the sensing core, the resolution FoM is 11.8 pJ & centerdot; K2 . A co-integrated dual-BJT TDC exhibits an inaccuracy of +/- 0.37 C-degrees (3 sigma), validating the effectiveness of the single-BJT approach for comparison. The TDC operates from a 2.0 to 5.5 V supply with low supply sensitivity of 2.54 m degrees C/V and supports a low standby current of 420 nA at 2.0 V, enabling compact size, high accuracy, and energy efficiency for duty-cycled applications.

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