Virtex-5 RocketIO GTP Transceiver User Guide
217
UG196 (v1.3) May 25, 2007
SelectIO-to-GTP Crosstalk Guidelines
R
•
If these SelectIO pins must be used for higher drive/higher speed applications, apply
power to the GTP transceiver analog supplies with a plane or wide buses a few layers
below the top of the board. Using a blind via to the GTP transceiver analog supplies is
better than using a through via. Shield these supply planes or buses with ground
planes above and below.
•
If a through via to supply the GTP transceiver analog supply pins must be used, use a
layer closes to the FPGA for routing signals to these vias. Route SelectIO nets in the
uppermost layer available after GTP transceiver high-speed signal and GTP
transceiver analog supply routing is implemented.
•
If supplying GTP transceiver power from the bottom of the board, route these
SelectIO nets in the highest available routing layer.
The absolute worst-case scenario would be to supply GTP transceiver analog supplies
from the bottom of the board and have all adjacent SelectIO outputs running at high drive
and high speed and routed to lower routing layers. For more information, refer to
for information on escaping of SelectIO adjacent to GTP
transceiver analog supply pins.
The SelectIO signals that have the largest impact on GTP transceiver performance are those
whose solder balls are adjacent to GTP transceiver analog supply solder balls (BGA
adjacency).
through
provide the GTP transceiver user with pin-
specific guidance recommendations to optimize GTP transceiver performance in the
presence of SelectIO switching. Specifically, the tables identify those pins which are either
1.0 mm or 1.4 mm away from an GTP transceiver analog supply pin and REFCLK pins. If
a pin is both 1.0 mm and 1.4 mm away from two different GTP transceiver analog supply
pins, then it is only listed in the 1.0 mm column.
Additionally, it is important to properly shield the traces or planes connecting the analog
supply vias to the supply filter network of the analog supplies from SelectIO escaping from
the BGA field. This is best done by placing GND planes above and below the layer
containing the analog traces or planes.
Table 10-6:
SelectIO Adjacent to Analog Supplies for (FF665 Packages)
GTP_DUAL
1 mm
1.4 mm
MGT116
E5
D5, F5, G4
MGT112
L5
K5
MGT114
U5
T5, W4
MGT118
AD4
AB5, AD5
Table 10-7:
SelectIO Adjacent to MGTCLK (FF665 Packages)
GTP_DUAL
1 mm
1.4 mm
116_REFCLK
D5
E5
112_REFCLK
K5
J5, L5
114_REFCLK
T5
R5, U5
118_REFCLK
AB5
AA5