Hi everyone,
I have a evaluation board which has FTDI FT2232 chip on it. I am confused about the connection of the crystal to the IC. Why they use 2.2k resistor, while there isn't any recommendation about this resistor in FT2232's datasheet.
It may be to control the drive level, or to limit current. I read something about that use of a series resistor a few years ago so had to search online to refresh my memory a little. The first two links (similar questions on other sites) and the second two (that are links to application note/tutorial-style pdfs) may be helpful.