The USB port supplies 4.2 to 5 V DC, so you can use the 18F4550 at this range as the minimum operating voltage is 4.2 V (with brownout disabled).
But why would you want to use 3.3 V for USB application ??
---------- Post added at 07:05 ---------- Previous post was at 06:31 ----------
The USB port supplies 4.2 to 5 V DC, so you can use the 18F4550 at this range as the minimum operating voltage is 4.2 V (with brownout disabled).
But why would you want to use 3.3 V for USB application ??