A PNP-Based Temperature Sensor With Continuous-Time Readout and ± 0.1 ∘ C (3 σ ) Inaccuracy From − 55 ∘ C to 125 ∘ C
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Abstract
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) Δ Σ -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
BE and in the ratio of the two resistors is digitally trimmed at room temperature (RT). Fabricated in a 0.18μ m CMOS process, the sensor occupies 0.12 mm
2, and draws 9.5μ 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 ± 0.1° C (3σ) from -55° C to 125° C, and a commensurate supply sensitivity of only 0.01° C/V. Furthermore, it achieves high energy efficiency, with a resolution Figure of Merit (FoM) of 0.85