How to choose FPGA Package - muneeb-mbytes/FPGABoard_edgeSpartan6 GitHub Wiki

  • First important step is to collect all requirements for your project, then weigh your requirements by importance (For example, if the most important issue is cost, that might make some FPGAs more appealing than others).

  • The decision while selecting FPGA should not be merely based on technical requirements but also commercial - a specific FPGA should not be chosen if it has too many resources or has too many IOs that are not required by the design. If so then the company money is simply wasted on expensive FPGA.

6 common criteria for selecting FPGA

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I/O Count

This basically means how many pins are required to connect from the FPGA to the external world. It’s always a good idea to add a few extra I/Os to the list to ensure having spare I/Os in case there is a need to make design changes if the future.

For TQG144 package the maximum user I/O is 102.

Number of Gates

There are different FPGA categories in the market and within each category there are different FPGA sizes (in terms of gates or resources). Large FPGAs cost much more than small FPGAs, therefore, choosing the smallest FPGA that the design can fit into and estimating the number of gates required is a skill.

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Operating Frequency

In general, an FPGA that run faster cost more money. All FPGA vendors have speed grading for their different FPGA offering and the goal is of course to find the cheapest FPGA that could meet all requirements. An FPGA speed grade is a maximum frequency at which a flip flop can run. For example, spartan6 has -1 -2 -3 etc. The speed grade influences various timing parameters in the FPGA, including LUT, I/O, and other parameters.

Operating Temperature

For most of the FPGA designs, this is not a problem. But if the work is in space, automotive or defense industry, this is a major issue. Taking FPGA to extreme operating temperatures means that FPGA vendor has been testing the FPGA and can guarantee it meets this extended requirements. For that reason, the FPGA that are used in extended temperature conditions may expect a cost increase.

Cost

The cost of an FPGA is an important factor to consider when selecting an FPGA package. However, the cost of an FPGA can increase with additional features. For example, the Spartan-7 series is very similar to the Artix-7 with the exception that there are no transceivers in Spartan-7, which makes it less expensive.

Vendors

There are four main vendors. The two large vendors: Xilinx and Altera (Intel). And two medium sized vendors: Lattice Semiconductor and Microsemi. There offering is similar but there are small difference.

If the FPGA product offering from various vendors is observed closely then you will see that some vendors have more clock signals or special blocks that could give you an edge, or some FPGA are more geared for high speed interface, etc.

Other factors to consider when selecting an FPGA package include

  • density
  • power dissipation and rails
  • package size
  • peripherals
  • expansion connectors
  • memory interfaces
  • ease of use
  • time to market
  • customization options more