Progress and advances in serial powering of silicon modules for the ATLAS tracker upgrade

It is expected that at SLHC the number of detector channels in the ATLAS Semiconductor Tracker will increase by a factor 10, to cope with the increased luminosity. Currently every detector module has its own power cable, known as independent power ing (IP). In the upgrade, this arrangement will no longer be tenable, due to cable volume and power losses. The serial powering alternative scheme, in which supermodules, with many readout hybrids, are connected in a serially powered chain, has been propo sed and actively pursued over the last few years by the ATLAS Tracker Upgrade Community. This scheme presents some benefits, including simplicity, lower mass and reduced power losses. On the other hand, grounding, shielding and data transmission schemes a re modified with respect to the conventional arrangement. Custom components specifically for serial powering have been produced, including the ABCN-25 readout ASICs and the SPI serial powering regulation ASIC, both in 250 nm CMOS, a dedicated programmable current source and power protection elements. In this paper the latest measurements from testing of the new custom electronics are presented and future plans are outlined.