A β-Compensated NPN-Based Temperature Sensor With ±0.1 °C (3σ) Inaccuracy From -55 °C to 125 °C and 200fJ · K² Resolution FoM
N.G. Toth (TU Delft - Electronic Instrumentation)
K.A.A. Makinwa (TU Delft - Microelectronics)
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Abstract
This article presents a CMOS temperature sensor that achieves both state-of-the-art energy efficiency and accuracy. An NPN-based front end uses two resistors to efficiently generate a PTAT and CTAT current, whose ratio is then digitized by a continuous-time (CT) Δ Σ -modulator. A β-compensation technique is used to mitigate base current errors associated with the NPN's finite β. Component mismatch and 1/f noise are mitigated by applying chopping and dynamic element matching (DEM), while the spread in VBE and the ratio of the two resistors are digitally trimmed at room temperature (RT). Fabricated in a 0.18-μ m CMOS process, the sensor draws 2.5μ A from a supply voltage ranging from 1.4 to 2.2 V. Measurements on 40 samples show that it achieves an inaccuracy of ± 0.1° C (3Σ ) from - 55° C to 125° C. Furthermore, it is both highly energy efficient, with a resolution figure of merit (FoM) of 200fJċK2 , as well as very compact, occupying only 0.07 mm2.