A Time-Domain SAR Smart Temperature Sensor With Curvature Compensation and a 3σ Inaccuracy of −0.4°C ∼ +0.6°C Over a 0°C to 90°C Range

• Published in: IEEE journal of solid-state circuits 2010-03, Vol.45 (3), p.600-609
• Main Authors: POKI CHEN, CHEN, Chun-Chi, PENG, Yu-Han, WANG, Kai-Ming, WANG, Yu-Shin
• Format: Article
• Language: English
• Subjects: Applied sciences; Approximation algorithms; Bipolar transistors; Calibration; Circuit properties; Circuits of signal characteristics conditioning (including delay circuits); Curvature compensation; Delay effects; Delay lines; Design. Technologies. Operation analysis. Testing; Electric, optical and optoelectronic circuits; Electronic circuits; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Exact sciences and technology; Integrated circuits; Linearity; Logic; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; smart temperature sensor; successive approximation register (SAR); Temperature measurement; Temperature sensors; thermostat; Time domain analysis; time-domain; time-to-digital converter; Transistors
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2010.2040658

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 mm 2 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.