CMOS time-mode smart temperature sensor using programmable temperature compensation devices and Delta Sigma time-to-digital converter

摘要

This work presents a time-mode smart temperature sensor in a standard 180 nm CMOS process, intended for on-chip thermal monitoring applications. A new temperature-to-pulse converter (TPC) is proposed utilising programmable temperature compensation devices, where a dual delay-line configuration is adopted, namely sensor and reference delay-lines. The proportional to absolute temperature (PTAT) delay offered by the sensor delay-line has a temperature coefficient (TC) of 720 ppm/ degrees C, whereas almost constant delay possessed by the reference delay-line has a TC of 60 ppm/ degrees C, over 0-100 degrees C temperature range. The proposed 1st-order Delta Sigma time-to-digital converter (TDC) serves as the smart sensor readout, where a novel delay-cell is proposed using multipath approach. The projected Delta Sigma TDC achieves 30 ns full-scale range at 9 ps resolution. The dual delay-line configuration in the TPC and the dynamic element matching in the Delta Sigma TDC bound the inaccuracy of the proposed smart temperature sensor to +/- 0.68 degrees C. The sensor shows a resolution of 0.03 degrees C at 0.5 mu s conversion time.