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 scalingdown 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 °C to 50 °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 μV and the power consumption is 240μW. 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.