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

Abstract

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/°C, whereas almost constant delay possessed by the reference delay-line has a TC of 60 ppm/°C, over 0–100 °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 °C. The sensor shows a resolution of 0.03 °C at 0.5 $$\upmu \hbox {s}$$ conversion time.