Newbie PCB

So one of the smaller FPGAs in the series...

I believe that some of the smaller ones have simpler to work with packages. BGA is likely not easy for a first try. (I haven't tried, so I can't really say.)

VGA doesn't need the top speed, but you still need to do some for both decoupling and impedance. Series termination is not so hard, and should work for VGA speeds. What else will your FPGA do besides drive a VGA? I can imagine a while graphical terminal, which should fit in a fairly small one.

Also some data input source?

(snip)

You should know a little about impedance matching before you do much electronics at all these days.

-- glen

The copper layer thickness requirement comes from current supply requirements. 50 ohms impedance on clock traces _hopefully_ only applies if you're going fast.

I don't know about which is better, but I would hazard a guess that if you're just running a 50MHz clock then you can get by with a lot less precision in the board than if you're trying to run right at the limit of the part. The biggest clock issue I'd be concerned with would be reflections causing false clocks, and that can be cured by putting your oscillator as close to the FPGA as you can get it, and/or terminating the clock line.

I would recommend using a leaded package, as those can, with only moderate difficulty, be soldered by hand. If you're willing to forgo being able to use all the pins, you may even be able to use a two-layer board, although it's probably smarter to go with at least a four-layer board with ground and power planes.

I think you could do this with EagleCad, if you're careful and know what you're doing.

The best thing you could do is to have a look at some of the schematics and gerber files from the Xilinx boards. Getting a schematic that is functionally correct shouldnt be too much of a problem but you need to be a bit more carefull with the pcb. The lower the frequency you use the easier things will be, so you may be better off sticking to around 50MHz for your first board. BGAs are not hard to work with, however you can forget about soldering them yourself. So if you plan to do the soldering yourself then use a non BGA package. I mainly use Xilinx devices but I doubt there is too much difference between them and Altera.

Jon

--------------------------------------- Posted through

I believe I have heard stories about people doing BGA in a toaster oven. No idea about the success rate, though.

-- glen

Yes, I think I've seen some videos in Youtube where people does BGA rework even with hot air. But no, definitely no; I'll stick with some QFP package I can do by hand, so preferably one without pad.

The thing is I noticed the 50-ohms impedance for the JTAG clock in the Spartan-6 Configuration guide, and then I found the excel spreadsheet for decoupling caps for the Cyclone IV power requirements. That's when I started wondering which one would give me somewhat of a bigger error margin. I'll go either with a Spartan 6 or 3A, or a cyclone IV, tqfp 100 or

Yes, I'll try to follow from some schematics I found, but on the other hand, I don't think is very easy to mimic PCB routing, maybe just for isolated parts like the VGA dac.

Thanks everyone, this is a really nice place to ask for help.

--------------------------------------- Posted through

Hello all,

HumanData in Osaka, Japan offer some Spartan3-AN and Spartan6 FPGAs, in BGA package, but on a nifty little breakout board that fits into a PLCC68 socket.

It's a tad expensive at 12,000 yen per unit (the FPGA itself is only maybe about 20 dollars in single unit prices on Digi-key) but then you don't have to worry about your carrier board being only two layers (or probably even hand wired on proto-board!), and for a hobbyist or otherwise one-off kind of thing, it would save you the cost of doing a four-layer board.

Plus, you can simply pop it out of the socket and reuse it as you please!

Here's a link:

Maybe not super economical, but it's an idea.

Cheers,

Steve

--------------------------------------- Posted through

I've just released a product that's very close to what you're looking for:

Price is $79 for one, cheaper for 3+ boards.

I has an FPGA big enough to hold a VGA controller plus a MicroBlaze microcontroller, 256Mb DRAM for your frame buffer, 62.5MHz clock, voltage regs, JTAG port for programming, configuration ROM, 38 break out pins.

You'd need to add the VGA DAC yourself, that would involve making a simple PCB with the VGA DAC and VGA connector to plug into the expansion connector (64 way edge connector with 38 available FPGA connections).

Stephen Ecob

Silicon on Inspiration

To be honest its not that expensive to get a BGA device soldered (I got one done for about $15). I would rather pay that then blow around $300 dollars on a pcb and device.

Jon

--------------------------------------- Posted through