Results from End-of-Substructure card production for the ATLAS ITk Strip upgrade using both the lpGBT-v1 and -v2 ASIC

Abstract The tracking system of the ATLAS experiment will be upgraded for the upcoming High-Luminosity Upgrade of the LHC (HL-LHC). The main building blocks of the new strip tracker are silicon-strip modules that consist of a sensor and hybrid PCB's. The modules are mounted on rigid carbon-fibre substructures, the so-called staves (petals) in the barrel (end-cap) regions, that provide common services to the modules. At the end of each stave or petal side, a so-called End-of-Substructure (EoS) card facilitates the transfer of data, power, and control signals between the modules and the off-detector systems. The EoS connects up to 28 data lines, each with 640 Mb/s, from the modules to one or two lpGBT chips that provide data serialization and use a 10 Gb/s versatile optical link (VL+) to transmit signals to the off-detector systems. The lpGBT also recovers the LHC clock on the downlink and generates clock and control signals for the modules. To meet the tight integration requirements in the detector, fourteen different EoS card designs are necessary. The power to the EoS is provided by a dedicated dual-stage DC-DC package providing 2.5 and 1.26 V to the EoS cards. A first production of almost 2000 EoS cards has been stopped due to the errors found in the lpGBT-v1 ASIC, but all accompanying DC-DC converters have been produced. We report on the production experience including detailed QC statistics and design validation (QA) results for the EoS itself with the lpGBT-v1 ASIC and how the two lpGBT issues were identified and how many EoS boards were affected by each. With the lpGBT-v2 ASIC now in hand, we report first QC results with the second production iteration.