Want to design a PCB with an FPGA on it?

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Lord Banshee

Joined: 18 Feb 2007
Posts: 24
Location: USA

05 Feb 2008 18:05 Want to design a PCB with an FPGA on it?

Want to design a PCB with an FPGA on it, but it seems i can not find "official" documents from Altera or Xilinx on how the pins should be connected. On most circuits i've used (simple ICs in comparison) there is always a typical circuit to go by. I've looked at some FPGA dev board schematics and it seems like the only resources i have, but i wonder if there was something from the vendors?

Any help would be great, or guide lines that i should follow, like how there is always many different size caps for noise isolation fro VCC to GND.

Thanks,
Chris

ep20k

Joined: 17 Sep 2002
Posts: 319
Helped: 15

05 Feb 2008 19:16 Re: Want to design a PCB with an FPGA on it?

xilinx

http://www.xilinx.com/support/documentation/index.htm

altera

http://www.altera.com/literature/lit-dp.jsp

ep20k

FvM

Joined: 22 Jan 2008
Posts: 5151
Helped: 766
Location: Bochum, Germany

05 Feb 2008 20:08 Re: Want to design a PCB with an FPGA on it?

Hello Chris,

unlike as you said "simple ICs" FPGA have most of their pins user configurable. There is little sense in giving application circuits, cause these pins can have nearly any function the developer want's them to. Some pins are dedicated, e. g. for configuration purposes. Example circuits for these pins can be found in device manuals and detailed application notes. Other documents discuss PCB design issues or special type of interfaces, e. g. for DDR-RAM.

The evaluation board documents, including layout files for some boards, are however a good starting point when you are planning a similar design. To my opinion, you should be able to design a FPGA board from the scratch, I did it myself some years ago and several times helped customers to take the first step.

But FPGA are rather complex and there are some design traps you may walk in. Thus it may be an alternative to start a prototype design based on an evaluation board. Some have daughter board connectors where your hardware could drop in. You can start code development on the evaluation platform and design your own board in parallel. If it isn't operational from the beginning (very likely) you have a reference to compare with.

Regards,
Frank

Lord Banshee

Joined: 18 Feb 2007
Posts: 24
Location: USA

05 Feb 2008 21:16 Re: Want to design a PCB with an FPGA on it?

i actually do have a couple fpga dev boards already, but the ones i have actually do not have any public schematics or layout documents (go figure). So maybe it would be a good idea to start with a dev board that has schematics and then build pcbs for my other circuits and once everything works great, integrate them all into one.

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FvM

Joined: 22 Jan 2008
Posts: 5151
Helped: 766
Location: Bochum, Germany

05 Feb 2008 21:28 Re: Want to design a PCB with an FPGA on it?

O.k., if you're using dev boards, you should know some basic design parameters: Pin mapping, power supply, configuration technique, also without having an exact schematic. And you can see many implementations details without an "X-ray view". I always learn from other designs, sometimes even from a photo. That could be a starting point for your design.