An SOI thermal-diffusivity-based temperature sensor with ±0.6°C (3Σ) untrimmed inaccuracy from −70°C to 170°C

This work presents the first thermal-diffusivity-based temperature sensor in SOI technology; it has an untrimmed inaccuracy of ±0.6°C (3π) from -70°C up to 170°C and uses up to 7x less power than prior art. The sensor uses an electrothermal filter (ETF) to measure the thermal diffusivity of silicon, D, which has a well-defined 1/T^1.8 temperature dependence. The ETF´s output is digitized by a phase-domain sigma-delta modulator. Measured data from several process lots show that that the sensor´s inaccuracy is limited by lithographic spread, and not by wafer-to-wafer or batch-to-batch variations.