A 2800-μm2 thermal-diffusivity temperature sensor with VCO-based readout in 160-nm CMOS

A highly digital temperature sensor based on the temperature-dependent thermal diffusivity of bulk silicon has been realized in a standard 160-nm CMOS process. The sensor achieves an inaccuracy of ±2.9°C (3a) from -35°C to 125°C with no trimming and ±1.2°C (3a) after a single-point trim, while achieving a resolution of 0.47°C (rms) at 1 kSa/s. Its compact area (2800 μm²) is enabled by the adoption of a VCO-based phase-domain ADC. Since 53% of the sensor area is occupied by digital circuitry, the sensor can be easily ported to more advanced CMOS technologies with further area reduction, which makes it well suited for thermal monitoring in microprocessors and other systems-on-chip.