MGT Link

Hi

I am designing two boards with virtex 4 fx devices fitted. They will stac one on top of the other using a board to board connector. The spacin between boards is about 20mms. Is it critical the type of connector that use to connect the MGT links between the boards. Do I need one of thes fancy 50 ohmn connectors or can I get away with something else? Is there way to simulate the effects that the connector will have?

Cheers

Jon

Reply to
maxascent
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yes

no.

Yes, but not just anything random. The impedance must match the impedance of your board routing.

Yes. Manufacturers like samtec publish electrical models of their connectors. You can get models of the FPGA-pins from Xilinx.

Read this:

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Kolja Sulimma

Reply to
comp.arch.fpga

First of all at what speed are you going to be running it? I have a design running multiple 3.36 Gbps links over a standard cPCI connector without any problem. I would say use something with small pitch and enclose each of your differential pairs in between GND pins and you will be fine... Ideally you'd need at least 3 rows of pins to fully enclose each of the pairs, but I am pretty sure it will work even with a single row connector. With such a short link there is a lot of margin.

/Mikhail

Reply to
MM

Thanks for all the advice. My link will be running at 3.25Gbps. I thin that I am going to use one of the santec board to board 50 ohm connectors.

Jon

Reply to
maxascent

One hint: you could also look at PCI-Express connectors and pinout as a reference. On PCIe, the pinout looks a lot like this:

Front ....... G G D1+ D1- G G D3+ D3- G ... Back ... G D0+ D0- G G D2+ D2- G G .......

Each differential pair is effectively surrounded by ground pins on all practically possible sides. Since PCIe 2.0 will use the same connectors (or slightly improved ones) to run at 4Gbps, these should be suitable for quite a bit more than 3.25Gbps if trace pairs are kept short and routed properly.

Reply to
Daniel S.

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