Serial Powering for Inner Tracker Detectors at the HL-LHC

The Large Hadron Collider will be upgraded to deliver peak instantaneous luminosities up to 7.5x10$^{34}$ cm$^{-2}$s$^{-1}$ and up to 4000\,fb$^{-1}$ during the 10-year High Luminosity phase (HL-LHC). New silicon tracking detector systems will be installed to fully exploit the physics potential of the upgraded machine. Inner tracker systems will be composed entirely of silicon pixel modules and capable of withstanding intense radiation environments while minimizing material in the detector region. Serial power distribution systems offer an attractive approach to fulfill the required granularity, radiation tolerance, and material constraints for these next-generation pixel detectors. This powering scheme is based on the use of Shunt Low Dropout regulators that will be integrated on the future pixel readout chip designed by the RD53 collaboration. Design choices for powering the inner tracker front-end electronics are discussed along with recent R\&D activities in novel serial powering schemes. First results from system tests of serial power chains with pixel readout chip prototypes are presented.