Stabilization and Protection of the Shunt-LDO regulator for the HL-LHC pixel detector upgrades

Serial powering is the baseline option for the pixel detectors in both the ATLAS and the CMS experiments targeting the phase II HL-LHC upgrade. The Shunt-LDO regulator is integrated in the front-end chips to generate the required supply voltages. A new compensation scheme has been developed to assure stable operation with large on-chip low-ESR (equivalent series resistance) load capacitances. A two-stage bandgap voltage reference circuit has been implemented to improve regulation performance. Security features have been added to protect against overvoltage and overload. Additional features have been added to allow regulator operation with small supply currents during the installation phase.