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This paper describes a time-domain temperature sensor based on a successive approximation algorithm. Without using any bipolar transistor, a temperature sensor composed of a temperature-dependent delay line (TDDL) is utilized to generate a delay proportional to the measured temperature. A binary-weighted adjustable reference delay line (ARDL) is adopted with an effective delay varied by a SAR control logic to approximate the TDDL delay for output coding. For linearity enhancement, a curvature compensation between both delay lines is invented to achieve the best ever accuracy among inverter-delay-based smart temperature sensors. With two-point calibration, a -0.4°C ˜ +0.6°C inaccuracy (3σ) over a 0°C ˜ 90°C temperature operation range has been measured for 23 test chips. With 10 output bits, the proposed sensor achieves a resolution better than 0.1°C and a chip area of 0.6 mm2 in a TSMC 0.35-μm standard digital CMOS process. The sensor's average current consumption is 11.1 μA at a conversion rate of 2 samples/s.