A CMOS temperature sensor based on duty-cycle modulation with calibration

In this paper, a digital CMOS temperature sensor based on duty-cycle modulation with digital calibration is presented. The temperature sensor generates a duty-cycle-modulated signal by applying a proportional to absolute temperature (PTAT) current and a complementary to absolute temperature (CTAT) current derived from substrate bipolar junction transistors (BJT) to an integrator followed by a window comparator. The duty-cycle-modulated signal is then converted to a digital representation of temperature with two counters. Calibration is performed in the digital domain with three calibration parameters. Dynamic element matching (DEM) and chopping techniques are also used to minimize the errors caused by the component mismatch. The prototype chip is fabricated in a 0.5 μ m CMOS process. The chip area occupies 2.3 mm 2 . Measurement results from 11 test chips show that an inaccuracy of - 1.1 - 0.5 ∘ C is achieved over the temperature range from - 35 to 85 ∘ C after calibration. The 2.5 V supply voltage is utilized and the total power consumption is 0.83 mW at a conversion rate of 0.5 kSa/s with a resolution of 0.0625 ∘ C/LSB , leading to 6.48 - nJ ∘ C 2 resolution figure of merit (FoM) and 2951.1 - nJ % 2 accuracy FoM.