A Resistor-Based Temperature Sensor With a 0.13 pJ·K² Resolution FoM
S Pan (TU Delft - Electronic Instrumentation)
Yanquan Luo (University of Ulm)
S Heidary Shalmany (TU Delft - Electronic Instrumentation)
K.A.A. Makinwa (TU Delft - Microelectronics)
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Abstract
This paper describes a high-resolution energy-efficient CMOS temperature sensor, intended for the temperature compensation of MEMS/quartz frequency references. The sensor is based on silicided poly-silicon thermistors, which are embedded in a Wien-bridge RC filter. When driven at a fixed frequency, the filter exhibits a temperature-dependent phase shift, which is digitized by an energy-efficient continuous-time phase-domain delta-sigma modulator. Implemented in a 0.18-μm CMOS technology, the sensor draws 87 μA from a 1.8 V supply and achieves a resolution of 410 μKrms in a 5-ms conversion time. This translates into a state-of-the-art resolution figure-of-merit of 0.13 pJ·K². When packaged in ceramic, the sensor achieves an inaccuracy of 0.2 °C (3σ) from -40 °C to 85 °C after a single-point calibration and a correction for systematic nonlinearity. This can be reduced to ±0.03 °C (3σ) after a first-order fit. In addition, the sensor exhibits low 1/f noise and packaging shift.