A 0.4 V, 19 pW Subthreshold Voltage Reference Generator Using Separate Line Sensitivity and Temperature Coefficient Correction Stages

Abstract

Sensor nodes and IoT systems require blocks that not only consume low power but also have good accuracy. Voltage reference generators are also considered important building blocks in sensor interface circuits. This paper presents a solution to increase the accuracy of low power subthreshold voltage generators by lowering the circuit sensitivity to temperature and supply voltage variations. The enhancement is achieved by using two separate stages for temperature coefficient (TC) and line sensitivity (LS) correction. A 0.18 {\mu}m standard CMOS process has been used for the proposed structure. The effects of parameter variations in the fabrication process are investigated using post-layout simulation and Monte Carlo analysis. In the supply voltage of 0.4 V to 2 V, an LS of 143.8 ppm/V is obtained. In typical corner conditions, the achieved TC is 7.45 ppm/{\circ}C over the temperature range of 0{\circ}C to 80{\circ}C. Due to process changes, and mainly affected by threshold voltage variations, the average TC can change to 39.2 ppm/{\circ}C. The minimum power consumption at 0{\circ}C and at a supply voltage of 0.4 V is 3.25 pW while the power consumption increases to 2.84 nW in 80{\circ}C and at the maximum supply voltage of 2 V.