DORIC. A front end clock and L1 distribution chip

DORIC has been designed to provide beam crossing (BCO) and L1 signals to the front end chips on ATLAS SCT detector hybrids. These signals are transmitted from the DAQ electronics down a single fibre to each hybrid. A pin diode provides the current input to DORIC from the optical signal at the fibre end. DORIC provides two outputs from this input signal, a 40 MHz BCO output, and a data output which contains L1 signals and any slow control data sent down the L1 line. The signals are sent down the fibre using pulse height modulation to encode the L1 and data signals onto the BCO. The BCO only produces a single height pulse, as does a BCO with data 0. A data 1 produces a double height pulse. The chip has been fabricated on Plessey´s WA process, a bipolar process which has been used for chips with a 10 MRad total dose. It will be tested and used in ATLAS beam tests