[...]- The FT2232 operates bus powered (works without having +12V connected).
Since you can't power the whole FPGA-array through one USB-port and we will need an external power-supply anyway, I'd suggest to also power the FT2232 from the power supply. Why? There are potential host-devices that can't even handle the minimum 100mA. For example an Android phone with a modified kernel to support host-mode ... would also be a very power-efficient host.
[...] Hi,
the idea behind host powered was simply to save one power supply (for 5V in the case of a FT2232D). How do these small devices provide USB host at all if they don't have 100mA? I thought the standard required at least that (and the chip would need less).