  A prototype Liquid-argon Trigger Digitizer Board (LTDB), called the LTDB
Demonstrator, has been developed to demonstrate the functions of the ATLAS
Liquid Argon Calorimeter Phase-I trigger electronics upgrade. Forty
Analog-to-Digital converters and four FPGAs with embedded
multi-gigabit-transceivers on each Demonstrator need high quality clocks. A
clock distribution system based on commercial components has been developed for
the Demonstrator. The design of the clock distribution system is presented. The
performance of the clock distribution system has been evaluated. The components
used in the clock distribution system have been qualified to meet radiation
tolerance requirements of the Demonstrator.
