A Sub-1.0-V On-Chip CMOS Thermometer With a Folded Temperature Sensor for Low-Power Mobile DRAM

Abstract

As Dynamic Random Access Memory (DRAM) supply voltages drop below 1 V with the scaling down of the process, it becomes increasingly difficult to construct a temperature sensor with sufficient accuracy to control self-refresh, without occupying significant area or consuming increased power. In this brief, we propose an on-chip CMOS thermometer with a temperature sensor, the output of which is divided into segments by a folding scheme. The slopes of these segments can be arranged to be the same or adjusted separately, as desired for the output. Implemented in a 29-nm DRAM process, the sensor operates from -40 degrees C to 95 degrees C at the supply voltage of 0.8 V, with a temperature sensitivity of -3.1 mV/degrees C between -40 degrees C and 35 degrees C, and -2.1 mV/degrees C between 35 degrees C and 95 degrees C. It has an area of 0.0016 mm(2) and consumes less than 0.144 mu W.