Delay-line based temperature sensors for on-chip thermal management

Integrated digital temperature sensors facilitate advanced thermal and power management. This paper reviews the integrated delay-line based temperature sensors, in terms of operating principle, the state-of-the-art power and area optimization and calibration methods. A self-calibration approach recently introduced will also be discussed in detail. This self-calibration method allows the automatic elimination of process variations and mismatches without the need for individual preprocess trimming as needed in traditional approaches. Measurement results for a 65nm CMOS delay-line based temperature sensor confirms an energy per conversion of 0.02 nJ with a resolution of 0.5 °C between 20 to 80 °C with a maximum error of ±2.0 ^oC. The active area of the temperature sensor is only 0.002 mm².