Xilinx RocketIO User Manual

Also see for RocketIO: User guide User guide User guide

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Xilinx RocketIO User Manual Manual pdf 111 page image

RocketIO™ Transceiver User Guide www.xilinx.com 111UG024 (v3.0) February 22, 2007PCB Design Requirements Rwith a transceiver from another vendor, termination voltage can be dictated by thespecifications of the other transceiver. In cases where the RocketIO transceiver isinterfacing with another RocketIO transceiver, any termination voltage can be used. WithAVCCAUXTX and AVCCAUXRX already powered with 2.5V, an obvious choice for VTTXand VTRX is 2.5V. However, it should be noted that when AC coupling is used, theoptimum value for VTRX is 1.7V. See “AC and DC Coupling” section for moreinformation.Passive FilteringTo achieve the necessary isolation from high-frequency power supply noise, passive filternetworks are required on the power supply pins. Figure 3-8 illustrates the difference inpower filtering networks between a device that does contain capacitors (Internal) and adevice that does not contain capacitors (External).Each transceiver power pin requires one capacitor and one ferrite bead. The capacitorsmust be of value 0.22 μF in an 0603 (EIA) SMT package of X7R or X5R dielectric material at15% tolerance, rated to at least 5 V. The ferrite bead is either the Murata BLM18AG102SN1or the Murata BLM15AG102SNID. These components may not be shared among multipleRocketIO power supply pins under any circumstances.Many of the Virtex-II Pro devices have power filtering capacitors incorporated into thepackage to reduce component count on the PCB and improve the effectiveness of thesecapacitors. Table 3-7 outlines which device/package combinations have 0.22 μF capacitorsinternal to the package and which devices do not. External ferrite beads must be used in allFigure 3-8: Power Filtering Network on Devices with Internal & External Capacitors2.5 VAVCCAUXTXAVCCAUXRXVTTXVTRXVTTVTR2.5 VAVCCAUXTXAVCCAUXRXVTTXVTRXVTTVTRDevice With In-Package Capacitors Device Without In-Package CapacitorsGNDAGNDAUG024_48_032805Product Not Recommended for New Designs