Design of 0.35 um CMOS Temperature Sensor for Automatic Refresh Cycle in DRAM Memory Cell

This paper proposes a low power CMOS smart temperature sensor which is composed of temperature-to-pulse generator (TPG), time-to-digital converter (TDC), and frequency selector. The multiple-block system is to obtain the self-refresh operation for a low power memory cell. Temperature-to-pulse generator (TPG) is composed with two delay-lines which are obtained by the circuit of CMOS inverter. The propagation delay time of CMOS inverter has a dependency on temperature. The inverter-based delay line and feedback topology are applied in TDC. The small-size time-mode temperature sensor is designed with 0.35-μm CMOS process. Six different digital outputs are obtained for the temperature ranges of -40 ~ 100 °C. Simulation test shows that the proposed temperature sensor is operated with the low power dissipation of 0.075 μW per sample and die-area of 0.06 mm2.