Radiation induced effects in the ATLAS Insertable B-Layer readout chip

The ATLAS Insertable B-Layer is the innermost pixel barrel layer of the ATLAS detector installed in 2014. During the first year of $pp$ collisions at $\sqrt{s} = 13~{\rm TeV}$ in 2015, an unusual increase was observed in the low voltage currents of the readout chips. This increase was found to be due to radiation damage to the chips. The dependence of the current on the total ionising dose and temperature has been studied using X-ray and proton beam sources, and will be presented in this note together with its possible parametrisation and operation guidelines for the detector.