Serial Powering for the Tracker Phase-2 Upgrade

The high luminosity phase of the LHC at CERN will bring unprecedented operational conditions for the experiments. To cope with the harsh radiation environment and extreme hit rates in the innermost layers of the detector, both ATLAS and CMS will upgrade their inner tracker pixel detectors. A serial powering distribution scheme is the only viable solution to supply them with the required current levels, within acceptable material budget and power cable losses. This powering scheme is based on the use of Shunt-Low Dropout regulators that will be integrated in the future pixel readout chip designed by the RD53 collaboration. In this paper, this scheme will be explained based on the implementation choices for the future CMS Inner Tracker. Its main system challenges will be discussed and first measurements with serially powered chains of prototype modules will be shown.