This brief presents a background digital calibration for comparator offset against temperature drift, which relies on the linearity characteristic of the offset versus temperature drift profile. While a reference comparator is introduced as the temperature tracking circuit, the calibration can work in the background without interrupting the normal operation. The calibration achieves a measured offset of < 400 μ V over a temperature range of-40 °C to 125 °C. Fabricated in 65-nm CMOS the chip prototype includes the calibration and works under a 1 V power supply.