I have been looking at two reference designs for the iMQ6Q:
iMX6 Sabre Board Rev C3, schematic available from the Freescale website.
Sabre Lite Board Rev D, schematic available at http://boundarydevices.com/sabre_lite-revD.pdf
The Sabre Board has an optional LDO with a note saying it "may be desired for NVCC_PLL_VOUT" (U9 on page 20). Similarly, the Sabre Lite Board feeds the NVCC_PLL_OUT pin from an external 1.2V LDO (U23 on page 2). However, the iMX6 documentation shows that there is an internal LDO for this pin and makes no mention of feeding it from an external LDO. Why might an external LDO be required?