Clock and data recovery methods for the readout control unit 2 in ALICE TPC

Abstract

The present ALICE TPC readout electronics consists of 4356 Front End Cards that are read out and controlled by a total of 216 Readout Control Units (RCUs). The RCU communicates with all sub-systems, in particular with the Timing, Trigger and Control (TTC) system, which provides each RCU with the 40.08 MHz LHC clock, which is used as a system and sampling clock in TPC readout electronics. The LHC clock and trigger data are sent over the TTC fiber using 80 Mb/s Time Division Multiplexed BiPhase Mark encoded signals. It is important to have a radiation tolerant solution to recover the clock with low jitter and with a predefined phase-offset to the LHC input clock. Presently, this is handled by the TTC receiver (TTCrx) ASIC sitting on the RCU.

First irradiation tests results of the ALICE TPC Readout Control Unit 2

“…With such a significant fluence rate, radiation induced effects can nevertheless be expected in clock distribution elements, memories and registers of the FPGA, in addition to external interfaces such as the DDL2 data link and the Trigger, Timing and Control (TTC) interface [12]. Irradiation campaigns are therefore necessary to investigate the radiation tolerance of the RCU2.…”

“…Three solutions for CDR functionality are considered for the RCU2 [12]: a custom CDR in FPGA, the Analog Devices ADN2814 and the TTCrx ICs. At TSL in Uppsala, the first two CDR solutions together with an optical receiver from Avago were irradiated.…”