Passive Filtering - Xilinx RocketIO User Manual

PCB Design Requirements

Passive Filtering

To achieve the necessary isolation from high-frequency power supply noise, passive filter networks
are required on the power supply pins.
networks between a device that does contain capacitors (Internal) and a device that does not contain
capacitors (External).
Device with in-package capacitors
2.5 V
VTT
VTR
Figure 3-8: Power Filtering Network on Devices with Internal and External Capacitors
Each transceiver power pin requires one capacitor and one ferrite bead. The capacitors must be of
value 0.22 µF in an 0603 (EIA) SMT package of X7R dielectric material at 10% tolerance, rated to
at least 5 V. The ferrite bead is the Murata BLM18AG102SN1. These components may not be
shared among multiple RocketIO power supply pins under any circumstances.
Many of the Virtex-II Pro devices have power filtering capacitors incorporated into the package to
reduce component count on the PCB and improve the effectiveness of these capacitors.
outlines which device/package combinations have 0.22 µF capacitors internal to the package and
which devices do not. External ferrite beads must be used in all cases, as ferrite beads are not
included inside the package in any device. Table boxes labeled "External" denote a device for which
the user must provide power filtering capacitors externally on the PCB; those labeled "Internal"
denote a device that contains all necessary 0.22 µF capacitors for RocketIO power pins. Table boxes
that say "No MGTs" denote a device that does not have any RocketIO transceivers.
RocketIO™ Transceiver User Guide
UG024 (v2.3.2) June 24, 2004
2.5 V
AVCCAUXTX
AVCCAUXRX
VTT
VTTX
VTR
VTRX
GNDA
www.xilinx.com
1-800-255-7778
Figure 3-8 illustrates the difference in power filtering
Device without in-package capacitors
AVCCAUXTX
AVCCAUXRX
VTTX
VTRX
GNDA
UG024_48_021704
Table 3-6
109
R