The ATLAS Tile Calorimeter digitizer

We describe a digitization and readout system built to serve 10800 PMT channels in the Atlas Tile calorimeter.Six or eight digitizer boards in each calorimeter module each receive six pairs of analog signals (high and low gain) to be digitized by 10-bit ADCs every 25 ns.Two custom designed gate arrays (CX-3161 from Chip Express) on each board each store data from three channels until validated by the first level trigger.Selected data are then formatted for subsequent read out.Clocks and control commands are distributed via the TTC system.The system is designed to achieve good fault and radiation tolerance.It was tested in test beam during summer 1999, and is intended for volume production in 2000.