3.3V supply for USB



I am new to Q2686 and also to implementing USB in my designs. For my first design with Q2686, a 3.3V power supply is required for RS232 level translator. Since I am deriving this 3.3V from VBATT, it is continuously available . My question is whether I can use this 3.3V for powering the USB (whether or not I actually make connection to any host). In effect, I shall not be making any physical connection to the host power supply. The logic behind this question stems from my doubt whether it’s necessary to extend signal & power simultaneously to the USB.
In short, can I keep the USB section powered-up without making a host connection ?

I shall be very much thankful for your comments.