Request for help to select an appropriate FPGA IC?

I don't know how to estimate how much logic you'll need, so it's hard to recommend a device.

If the logic is small enough, I'd go for a MAX II or MAX V device.

They're the cheapest, have a small EEPROM I think will be useful for you and require the fewer external components.

You can download, for free, Quartus and start putting together a prototype design before committing to device.

If you need a bigger device, the option is the Cyclone III E or LS or Cyclone IV E family.

These are more expensive and require more external components, including an external EEPROM.

The Cyclone III LS family has the advantage of allowing the configuration (which is stored in the external EEPROM) to be encrypted. But this requires a small battery to keep the decrypting key in the FPGA.

Regarding external components...

Configuration:

- MAX II/MAX V require a connector and a couple of resistors for JTAG; ; you may also want to have a JTAG interface for the Cyclones.

- Cyclone srequire an external EEPROM and a couple of resistors for the FPGA configuration interface.

Voltage regulators, depending on your system and device.

Some MAX II devices can be operated using only a single 3.3V supply.

Other MAX II/V will need a 1.8V supply, plus 3.3V if you want 3.3V I/Os.

Cyclones will need even more supplies..

Level shifters: the MAX II/V and Cyclone FPGA can only handle signals up to 3.3V.

If you need 5V or more, you may need more components.