Hi Warren,
Yes, unfortunately probably not the answer you were looking for. The datasheet does seem to "suggest" a ground plane is required with the strong recommendation on page 176 - in the section titled PCB Design Considerations: "A solid ground plane is a necessity for maintaining signal integrity and minimizing EMI radiation" and "Use a single ground plane in the application layout."
You might also find application note AN-772 handy, which contains some additional board design considerations for the LFCSP package
-JT
