Building a virtex 7 pcb - Page 1
Forum section: electronics / general

author: ultrathom
author_rank: Contributor
timestamp: January 26, 2014, 09:36:30 am
content: Hi all,I would like to build a PCB with a Virtex 7 chip which I have.What I want is a footprint for the part, and the most basic layout for power. I thought about taking the gerber files they provide and stripping out the components I don't need. They supply gerbers for allegro. Is there a easier way ?

author: Dago
author_rank: Frequent Contributor
timestamp: January 26, 2014, 03:39:14 pm
content: If you need to ask then you can't do it.How would you even solder a BGA?

author: JoeN
author_rank: Frequent Contributor
timestamp: January 27, 2014, 03:04:39 am
content: Virtex 7s have a bunch of different pin counts (I see devices with 1157 through 1930 pins), all BGA. You have to tell us the specific chip. Once you have a board made, you have to be able to solder a BGA, probably one with a 1000+ pin count, which means a reflow oven. Are you up to that?The best way to approach this, IMHO, having done some things approaching this (but not on such a large part) is to find a schematic for a development board from any serious manufacturer. Base your design on that. What could go wrong at that point?For example, I enter "virtex 7 development board" into Google and soon find this:A development board schematic based on Virtex 5:http://www.digilentinc.com/Data/Products/GENESYS/Genesys-sch.pdfXilinx Virtex 7 Development Board VC707 schematics, based on the 1761 pin XC7VX485T-2FFG1761C device:http://esimioni.web.cern.ch/esimioni/files/EvalOptoMezzanine/backup/vc707_Schematic_xtp135_rev1_0.pdf(you may want to save this, this is password protected at Xilinx and I don't think these guys are supposed to have it available on the Intertubes.)And after all of that, you will maybe be able to get the time-limited 30 day eval software you need to program it. The free version will not work. If you figure out how to get the full-feature-time-limited software to work past the 30 day limit, please tell me. It's your duty to do so since I gave you some solid pointers here.

author: poorchava
author_rank: Super Contributor
timestamp: January 27, 2014, 07:54:02 am
content: I'd guess minimum of 6 layers pcb, most likely 8 or more for up-to-spec operation.Start with spartan 6 or something.Where did you get that chip anyway? Those are several thousands of dollars apiece in retail.

author: JoeN
author_rank: Frequent Contributor
timestamp: January 27, 2014, 08:06:06 am
content: Code:Quote from: poorchava on January 27, 2014, 07:54:02 amI guess I shouldn't be answering this for another guy, but even very high-end FPGAs are always available used/for recovery on eBay, usually literally pennies on the dollar. Unguaranteed, of course. Good luck to your desoldering/reballing/resoldering efforts.http://www.ebay.com/sch/i.html?_nkw=virtex+recoveryI don't see any 7s right now but I have seen them before.Good point about the 6/8 layer issue. There are places that do cheap 4 layers now but the price goes up enormously for 6/8 layer. It might be more economical to keep an eye out on eBay for a used development board than doing that.

author: tszaboo
author_rank: Super Contributor
timestamp: January 27, 2014, 10:34:45 am
content: Quote from: JoeN on January 27, 2014, 08:06:06 amSome applications, you can omit the usage of the pins in the middle of the FPGA. Than you can route it on a 4 layer board, and the cost will not be that much anymore. That is why we always cry for QFP packages at the FPGA companies, no response of course.

author: JoeN
author_rank: Frequent Contributor
timestamp: January 27, 2014, 07:34:10 pm
content: Quote from: NANDBlog on January 27, 2014, 10:34:45 amI wonder why there hasn't been more adoption of the dual-row VTLA packages. They have pretty decent pin density and can be routed out very easily. Microchip uses this package for at least one of their devices.VTLA-124:

author: scientist
author_rank: Frequent Contributor
timestamp: January 30, 2014, 10:59:03 pm
content: OP, can you respond? Or are you too busy trying to PTH solder the BGA?