Passive Filtering - Xilinx RocketIO User Manual

Product Not Recommended for New Designs
PCB Design Requirements
with a transceiver from another vendor, termination voltage can be dictated by the
specifications of the other transceiver. In cases where the RocketIO transceiver is
interfacing with another RocketIO transceiver, any termination voltage can be used. With
AVCCAUXTX and AVCCAUXRX already powered with 2.5V, an obvious choice for VTTX
and VTRX is 2.5V. However, it should be noted that when AC coupling is used, the
optimum value for VTRX is 1.7V. See
information.

Passive Filtering

To achieve the necessary isolation from high-frequency power supply noise, passive filter
networks are required on the power supply pins.
power filtering 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 & 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 or X5R dielectric material at
15% tolerance, rated to at least 5 V. The ferrite bead is either the Murata BLM18AG102SN1
or the Murata BLM15AG102SNID. 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.
internal to the package and which devices do not. External ferrite beads must be used in all
RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
2.5 V
AVCCAUXTX
AVCCAUXRX
VTT
VTTX
VTR
VTRX
GNDA
outlines which device/package combinations have 0.22 μF capacitors
Table 3-7
www.xilinx.com
"AC and DC Coupling" section for more
Figure 3-8 illustrates the difference in
Device Without In-Package Capacitors
AVCCAUXTX
AVCCAUXRX
VTTX
VTRX
GNDA
R
UG024_48_032805
111