I'm designing a device which uses an FT201X USB I2C bridge for driving a series of LED controllers. The total LED current would far exceed the few hundred milliamps that a USB port will allow me to consume.
Figure 8.1 in the datasheet shows a typical usage diagram. If I wish to use a separate switch-mode supply to power the entire device, am I correct in thinking that I should just ignore the +5VDC rail on the USB device, and instead feed the 5VDC from my switch-mode supply into the VCC of the FT201X, and connect the switch-mode supply's ground to the GND pin on the USB connector?
My concern is that, since the USB port is going to be connected to an SMPS internally on the motherboard/PSU, I'd be bridging the grounds of two switch-mode supplies. I've read that this can be problematic, causing ground loop issues.
Is this likely to be a problem? If so, is there a standard way to implement galvanic isolation of the USB data lines?