Performance and description of the upgraded readout with the new back-end electronics for the ATLAS Pixel detector

LHC increased drastically its performance during the RUN2 data taking, starting from a peak instantaneous luminosity of up to $5\times10^{33} \mathrm{cm}^{-2} \mathrm{s}^{-1}$ in 2015 to conclude with the record value of $1.4\times10^{34} \mathrm{cm}^{-2} \mathrm{s}^{-1}$ in November 2016. The concurrent increase of the trigger rate and event size forced the ATLAS experiment to exploit its sub-detectors to the maximum, approaching and possibly overcoming the design parameters. The ATLAS Pixel data acquisition system was upgraded to avoid possible bandwidth limitations. Two upgrades of the read-out electronics have been done. The first one during 2015/16 YETS, when the outermost pixel layer (Layer-2) was upgraded and its bandwidth was doubled. This upgrade partly contributed to maintain the data taking efficiency of the Pixel detector at a relatively high level ($\sim$99%) during the 2016 run. A similar upgrade of the read-out system for the middle layer (Layer-1) is ongoing during 2016/17 EYETS. The details of the Pixel DAQ upgrades, the performance of the Layer-2 during the 2016 run and the status of the Layer-1 upgrade are presented in this poster.