27.5: A $4,\ 100\mu\mathrm{m}^{2}$ Wire-Metal-Based Temperature Sensor with a Fractional-Discharge FLL and a Time-Domain Amplifier with $\pm 0.2^{\circ}\mathrm{C}$ Inaccuracy $(3\sigma)$ from −40 to $125^{\circ}\mathrm{C}$ and $45\text{fJ}\cdot \mathrm{K}^{2}$ Resolution FoM in 28nm CMOS

Resistance-based temperature sensors feature a compact area $(< 5,000\mu \mathrm{m}^{2})$ [1]–[3] with high accuracy and superior resolution FoM $(< 100\text{fJ} \cdot \mathrm{K}^{2})$ [4], [5]. In contrast to the sensing element using active devices (e.g., BJT and MOSFET) that require biasing, the resistor does not pose restrictions on the $V_{\text{DD}}$. Such property facilitates the deployment of resistor-based temperature sensors in the advanced processes with core $V_{\text{DD}} < 1\mathrm{V}$ (e.g., 0.9V in the selected 28nm process) for integrated-temperature-sensing solutions. Yet, due to the transistors' pronounced non-ideal characteristics (gate tunneling, leakage current, short-channel effect, etc.), achieving decent competitive resolution FoM (R-FoM) with a compact area while upholding accuracy remains a significant challenge [6].