A close-loop time-mode temperature sensor with inaccuracy of −0.6°C/0.5°C from −40°C to 120°C

This paper presents a high linearity time-mode temperature sensor with close-loop architecture. The main loop utilizes a switched-capacitor equivalent resistor (Reqsc) to convert the linear values of ΔVBE and the output period of a Voltage-Controlled-Oscillator (VCO) into the control voltage of the VCO. A temperature independent equivalent resistor (Req) whose value only depends on clock period and capacitor value is built to overcome the PVT variations. When Req is equal to Reqsc, the output periods of the VCO which only contains capacitors' ratio are linear with temperature values. Based on the existence of close loop feedback, the proposed temperature sensor achieves excellent temperature linearity. The gain-enhanced and offset-free integrator is adopted, the design requirements of the VCO and reference clock are significantly relaxed. Within the temperature range of -40 °C to 120 °C, the output periods achieve equivalent temperature error of -0.6 °C/0.5 °C with two-point calibration.