I couldn't tell you, and I apologize for being idiomatic. I found 3 out of the 30 or so chips they make with a cursory glance. So at least 10%?
What I can tell you however is it's a "Typical Application" in a few of their products (FT245R, UM232R, MM232R)[1], FTDI comes up in trusted computing chip vendor discussions[2], and they go so far as to provide reference designs [3] which is enough to infer it's non-trivial.
While I don't have any love lost for them, they do have a USB-to-Parallel chip which could have saved the author a lot of work [4].
What I can tell you however is it's a "Typical Application" in a few of their products (FT245R, UM232R, MM232R)[1], FTDI comes up in trusted computing chip vendor discussions[2], and they go so far as to provide reference designs [3] which is enough to infer it's non-trivial.
While I don't have any love lost for them, they do have a USB-to-Parallel chip which could have saved the author a lot of work [4].
[1] http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_...
[2] http://www.eetimes.com/document.asp?doc_id=1251578 & https://www.bertin-it.com/brochure/WP-BadUSB_an-unpatchable-...
[3] http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_...
[4] http://www.ftdichip.com/Products/ICs/FT245BM.htm