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Got problems going the distance with 28Gbps data lines on Xilinx-based systems? Answers in Samtec’s New FireFly Design Guide

Xilinx Employee
Xilinx Employee
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The steep attenuation of 28Gbps signals on pcbs cause problems for every system designer trying to deal with high-speed serial interfaces. Samtec’s new brochure titled “Samtec Products Supporting Xilinx Virtex UltraScale+ FPGA VCU118 Development Kit” sums up the problem in just one graphic:

 

 

High-Speed Signal Attenuation.jpg 

 

 

The best you can hope for with a pcb (the dark blue line) is about half a db of attenuation per trace inch for a pcb manufactured using PTFE laminates, which were originally developed for microwave and RF applications. Up there at the top of the graph, showing far less attenuation, you see Samtec’s solution: its Twinax FireFly interconnect system, which is designed to carry these high-speed data signals within a system. (For essentially no loss, there’s a compatible optical FireFly module, shown for comparison at the very top of the graph.)

 

This next table, also taken from the Samtec brochure, sharpens the picture even more:

 

 

 

FireFly Performance Table.jpg 

 

 

As the table shows, if you are dealing with 28Gbps transceiver signals (and soon perhaps 56Gbps) and you need to go more than a very few inches, then you’ll want to consider the Samtec FireFly Micro Flyover system.

 

An easy way to experiment with the Samtec FireFly Micro Twinax interconnect system is to use the company’s FMC+ Active Loopback card, which is included with the Xilinx VCU118 Virtex UltraScale+ FPGA Dev Kit. Here’s a photo of that card plugged into the FMC port of the VCU118 Dev Kit:

 

 

 

Xilinx VCU118 Dev Kit for UltraScale Plus with Samtec FireFly Micro Flyover FMC Card.jpg

 

Xilinx VCU118 Virtex UltraScale+ FPGA Development Kit with Samtec FireFly Micro Flyover FMC Card

 

 

 

Note that one end of the FireFly Twinax cable is connected to this FMC card and the other end plugs into a FireFly connector already present on the Xilinx VCU118 Dev Kit’s FPGA board.

 

Samtec has a new 12-page FireFly Application Design Guide that provides more details.

 

 

For previous Xcell Daily blog posts about the Samtec FireFly interconnect system, see:

 

 

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