A 65nm CMOS Technology Radiation-Hard Bandgap Reference Circuit

This paper presents a BandGap reference circuit with low sensitivity to temperature and to the voltage supply variations. It has been designed to be Radiation-Hard up to 1 GRad. This voltage reference has been developed in a commercial 65nm CMOS technology with 1.2 V of nominal voltage supply. A current-mode architecture has been chosen to allow the low-voltage operation. Particular attention has been dedicated to circuit radiation hardness, in order to provide a stable voltage signal also with high radiation levels, like that of high-energy physics experiments. One of the advantages of CMOS scaling-down process is that the effects, due to radiation exposure, steadily decrease making circuits more and more robust. It follows that, in a conventional BandGap circuit, the most critical aspect could regard the diodes, or in general, the sensing elements. This design has been preceded by a series of measurements of two different sensing device in order to use that with the better radiation hardness. The BandGap reference circuit has been simulated with temperature range from -10 degrees C to 50 degrees C. The output value is around 330 mV with a curvature error of 0.05% in nominal conditions. The maximum output deviation in the absolute value is about +/-1.1% and +/-1.6% under process and mismatch respectively. The integrated noise from 0.01 Hz to 100 MHz is about 180 mu V and the power consumption is 240 mu W. The radiation effects have been simulated modifying the models of devices according to measurements. In this case, thanks to a proper sizing, the output voltage shift is of a few millivolts.