RocketIO™ X Transceiver User Guide www.xilinx.com 117UG035 (v1.5) November 22, 2004 1-800-255-7778PCB Design Requirements RVTRX. The ferrite beads are mounted at the 16 “L[n]” locations (highlighted by the coloredcircles).All AVCCAUXTX and AVCCAUXRX pins in a Virtex-II Pro X device must be connected to2.5V/1.5V regardless of whether or not they are used. See “Powering the RocketIO XTransceivers,” page 121 and “POWERDOWN Port,” page 121 for details.High-Speed Serial Trace DesignRouting Serial TracesAll RocketIO X transceiver I/Os are placed on the periphery of the BGA package to facilitaterouting and inspection (since JTAG is not available on serial I/O pins). RocketIO Xtransceivers have a 50Ω output/input impedance. Controlled impedance traces should beused to connect the RocketIO X transceiver to other compatible transceivers.When routing a differential pair, the complementary traces must be matched in length to asclose a tolerance as is feasible. Length mismatches produce common mode noise andradiation. Severe length mismatches produce jitter and unpredictable timing problems atthe receiver. Matching the differential traces to within 50 mils (1.27 mm) produces a robustdesign. Since signals propagate in FR4 PCB traces at approximately 180 ps per inch, adifference of 50 mils produces a timing skew of roughly 9 ps. Use SI CAD tools to confirmthese assumptions on specific board designs.Figure 4-23: Example Power Filtering PCB Layout for Four MGTs(In Device With Internal Capacitors), Bottom Layerug)35_ch4_23a_021304
