On-chip oscillator based temperature-to-digital converter exploiting channel length modulation coefficient λ

Abstract

This work presents a fully integrated, self-clocked temperature-to-digital converter-based smart temperature sensor for thermal monitoring of SoC for self-heating problem. The design utilizes the channel length modulation coefficient λ with MOSFET sensing followed by a time-to-digital converter (TDC). The proposed method considers the ratio of saturation currents of two nMOSFETs with constant gate voltages but different gate lengths. At a CMOS process of 90-nm and supply voltage of 1.1 V, the sensor occupies a small area of 0.047 mm2. The sensor further attains a resolution of 0.036OC over a temperature range of −40OC to 100OC and limits the inaccuracy between −0.79OC and 0.78OC after two-point calibration.