A 65 nm Rad-Hard Bandgap Voltage Reference for LHC Environment

A radiation-hard BGR (bandgap voltage reference) circuit is here presented. It's able to maintain the output voltage accuracy over process, voltage, and temperature (PVT) variations, combined with extremely high total-ionizing-dose (up to 800 Mrad (SiO2)), as required by the next experiments upgrades of the Large Hadron Collider (LHC). The design has been dealt starting from several experimental results, collected from some testing devices, under radiation exposure. In particular, this information has been used modifying the model files provided by foundry, in order to consider the radiation exposure effects during the design process. Consequently, a rad-hard optimized sizing device has been devised. In addition, a particular layout solution has guaranteed a better radiation immunity for the temperature sensing elements (i.e., diodes). The bandgap reference circuit has been fabricated in a commercial 65 nm CMOS technology. Measurement results show a temperature coefficient of about 130 ppm/°C over a temperature range of 120 °C (from -40 °C to 80 °C, as required by application) and a variation of 0.3% for Vdd 1.08 V-1.32 V. The mean value of the BGR output is about 330 mV, with a 10% maximum shift when exposed up to 800 Mrad (SiO2). The power consumption is 240 μW at room temperature, with a core area of 0.018 mm2.