I'm looking for an similar FPGA with XILINX XC3020A-7PC84C to replace with it.
i want to do this replacement with minimum changes in circuit design.
I checked XILIINX web site and i found out new generation of their products doesn't work with 5 V level and this is a tragic difference.
Can someone help me to find a good choice for this replacement.
From your description I am sure you would have already gone through Xilinx product line. As Technology nodes change 5V IO is not being supported. Obviously some alternatives exist. For example you could use a low end 3.3V Spartan6 FPGA and replace external IO logic with 3.3V/5V ICs if feasible and this assures minimal changes to schematic. If not feasible Level translators have to be used with FPGA. If schematic is shareable more specific alternatives could be suggested.
Another big difference between a newer chip and what you have is the tools. I bet the content of that FPGA was defined as a schematic? That will all have to be re-engineered into any new device (very likely as HDL, but perhaps some of the other vendors still have schematic capture?)
Have you looked at non-Xilinx replacements? Lattice still have some 5 V tolerant parts I think. The number of flip-flops in the 3020 is probably within reach of a large CPLD-type device - depending on the logic associated with them, it might fit?
Can you give some idea as to what functions the logic in the current device provides?
I agree with what has been said about the tools and the design entry. Something else you need to consider is that IC's are super fast these days compared to the 3020. Even if you could find a replacement in an 84-pin PLCC package, I would be concerned about the adequacy of the decoupling capacitors on your board, and even more concerned about the edge rates of the I/O signals (without knowing the lengths of your traces and the interfacing electronics). Some FPGA's such as the Spartan6 have selectable I/O drive strengths, so you might find something like that in a 5V part from Lattice or MicroSemi. If I were tasked with replacing it and I couldn't find a suitable replacement, I would make a module using a PCB with castellations that you could solder down on your board.
Here is a picture of an example of what I'm talking about:
I would use older technology buffer IC's that match the I/O specs of the 3020 (i.e. 74HC/HCT series).
But it might be a lot simpler to purchase 3020's instead of replacing them. I did a search on Octopart and there are some available:
Without knowing more about the design, that is my first impression.