Realisation of serial powering of ATLAS pixel modules

Modern hybrid pixel detectors as they will be used for the next generation of high energy collider experiments like LHC avail deep sub micron technology for the readout electronics. To operate chips in this technology low supply voltages of 2.0 V to 2.5 V and high currents to achieve the desired performance are needed. Due to the long and low mass supply cables this high current leads to a significant voltage drop so that voltage fluctuations at the chip result, when the supply current changes. Therefore the parallel connection of the readout electronics with the power supplies imposes severe constraints on a detector with respect to voltage fluctuations and cable mass. To bypass this problem a new concept of serially connecting modules in a supply chain was developed. The basic idea of the concept, the potential risk and ways to minimize these risks are presented. In addition, studies of the implementation of this technology as an alternative for a possible upgrade of the ATLAS pixel detector are shown. In particular, it is shown that the operation of several module in a supply chain does not affect the stability, the reliability and the performance of the ATLAS pixel modules