Hi Ant,
You need to run it at 3.3v output. Go back over your CD6003 thread, there is info there from myself and Martin.
Unless you have other ideas?
Ideas?.... I had a good look at the scematic and there are 2 regs for the XO IC supply, 1 x 3.3v quite a distance away for IC output which splits to 1.8v kia reg for the IC supply.
In a rush.
More detail later.