A BJT-Based Temperature Sensor Achieving an Inaccuracy of ±0.3°C (3σ) and a 6.605 pJ∙K² Resolution FoM in 28-nm CMOS

This paper describes an accurate BJT-based temperature sensor fabricated under 28-nm CMOS process: the analog front end (AFE) and bias circuit feature low noise and high precision techniques. Source degeneration is adopted to mitigate noise, while chopper and dynamic element matching (DEM) are used to reduce mismatch. The $\beta_{F}$ compensation is also integrated to reduce non-linearity caused by the low current gain $\boldsymbol{\beta}_{\mathrm{F}}$ of the substrate BJT in nanometer CMOS technology. The discrete-time $\Sigma \Delta$ modulator applies chopper and correlated double sampling (CDS) to eliminate mismatch and noise effectively. Thanks to these techniques, the sensor achieves an accuracy of $\pm 0.3^{\circ} \mathrm{C}$ within the test range of $0^{\circ} \mathrm{C}$ to $80^{\circ} \mathrm{C}$ after single-point trimming. The sensor’s resolution figure of merit (FoM) stands at $6.605 \mathrm{pJ} \cdot \mathrm{K}^{2}$. It takes 4.27 ms to complete a conversion round with a resolution of $0.01^{\circ} \mathrm{C}$ and consumes $15.48 \mu \mathrm{~W}$ power.