High linear voltage references for on-chip CMOS smart temperature sensor from-60 degrees C to 140 degrees C

Abstract

A low-cost and high linear voltage reference circuitry is designed and implemented in TSMC 0.18 mu m CMOS technology. Previous research has proposed the use of MOS transistors operated in the weak inversion region to replace the bipolar devices with conventional PTAT (proportional to absolute temperature) circuits. However, such solutions often cause linearity problem in high temperature region because of the current leaking devices in modern deep sub micron and nano-scale CMOS technology. The proposed circuit utilized temperature complementation technique on two voltage references, PTAT and IOAT (independent of absolute temperature) references, to enhance the linearity and produce a stable IOAT voltage reference. Based on the measurement results, the R-square of PTAT reference is better than 0.9 and the temperature coefficient of IOAT reference is 14 ppm/degrees C in a considerable wider temperature range from -60 degrees C to 140 degrees C. The occupied chip area is 0.00126 mm(2). Thus, a fully integrated temperature sensor with wider temperature range is designed and easily to integrate to modern system-on-chip designs with minimal efforts.