A 210 nW NPN-Based Temperature Sensor With an Inaccuracy of ±0.15 °C (3σ) From −15 °C to 85 °C Utilizing Dual-Mode Frontend

This paper describes an NPN-based temperature sensor that achieves a 1-point trimmed inaccuracy of ±0.15 ∘C (3σ) from –15 to 85 ∘C while dissipating only 210 nW. It uses a dual-mode front-end to roughly halve the power consumption of conventional front-ends. First, two NPNs are used to generate a well-defined PTAT bias current, then this current is sampled and applied to the same NPNs to generate well-defined PTAT and CTAT voltages. These voltages are then applied to a low power tracking Σ modulator-based ADC, which employs a digital filter to efficiently generate a multi-bit representation of temperature. A prototype fabricated in a 180-nm BCD process achieves 15 mK resolution in a 50 ms conversion time, which translates into a state-of-the-art resolution FoM of 2.3 pJK2.