A PNP-Based Temperature Sensor With Continuous-Time Readout and ±0.1 ∘C (3σ) Inaccuracy From -55 ∘C to 125 ∘C

This article describes a PNP-based temperature sensor that achieves both high energy efficiency and accuracy. Two resistors convert the CTAT and PTAT voltages generated by a PNP-based front-end into two currents whose ratio is then digitized by a continuous-time (CT) $\Delta \Sigma $ -modulator. Chopping and dynamic-element-matching (DEM) are used to mitigate the effects of component mismatch and 1/f noise, while the spread in $V_{\mathbf {BE}}$ and in the ratio of the two resistors is digitally trimmed at room temperature (RT). Fabricated in a $0.18~{\mu }$ m CMOS process, the sensor occupies 0.12 mm2, and draws $9.5~{\mu }$ A from a supply voltage ranging from 1.7 to 2.2 V. Measurements on 40 samples from one batch show that it achieves an inaccuracy of ${\pm } 0.1~{^{\circ }}$ C ( $3{\sigma }$ ) from ${-} 55~{^{\circ }}$ C to $125~{^{\circ }}$ C, and a commensurate supply sensitivity of only $0.01~{^{\circ }}$ C/V. Furthermore, it achieves high energy efficiency, with a resolution Figure of Merit (FoM) of 0.85 pJ $\cdot $ K2.