DUE board USB voltage input sanity check

Development Tools IDE 1.x
1

I am comparing the Due schematic (Arduino_DUE_V02b) with the Atmel reference design (SAM3X-EK) and noticed that the Due schematic the VUSB is at 5 volts where the Atmel ref design goes through a 5-3.3v converter to the vbus. Am I missing something? I double checked the datasheet for the SAM3x series chips (SAM3X_doc11057) and the max DC ratings don't specify a 5v tolerant rail.

Sanity check would be great.

Thanks.

Below are the links to the referenced docs:
Atmel site: http://www.atmel.com/tools/SAM3X-EK.aspx?tab=documents
Due schematic: http://arduino.cc/en/uploads/Main/arduino-Due-schematic.pdf

2

In the datasheet the USB 5V is used for a 3.3V(VDD) this is not used for VBUS, which is directly supplied by the USB 5V.