1650μm2 Thermal-Diffusivity Sensors with Inaccuracies Down to ±0.75°C in 40nm CMOS

Abstract

This work presents a thermal diffusivity (TD) sensor realized in nanometer (40nm) CMOS that demonstrates that the performance of such sensors continues to improve with scaling. Without trimming, the sensor achieves ±1.4°C (3σ) inaccuracy from -40 to 125°C, which is a 5× improvement over previous (non-TD) sensors intended for thermal monitoring. This improves to ±0.75°C (3σ) after a single-point trim, a level of accuracy that previously would have required two-point trimming. Furthermore, it operates from supply voltages as low as 0.9V, and occupies only 1650 μm2, making it one of the smallest smart temperature sensors reported to date. These advances are enabled by the use of a phase-calibration scheme and a highly digital phase-domain ΔΣ ADC.