Low voltage supply system for the very front end readout electronics of the CMS electromagnetic calorimeter

The CMS electromagnetic calorimeter requires about 113 kW at 2.5 V to power the custom designed readout chips in 0.25 μm technology. The power is converted to low voltage DC at the periphery of the CMS magnet and distributed by copper buses over ∼ 25 m to the detector. Low voltage regulator cards using radiation hard low voltage regulators from CERN/ST microelectronics provide the power to the readout cards. The power is delivered floating and is grounded at the detector end. Several regulator cards were produced and tested.