Help needed! can I connect cycloneIII's GNDA with digital ground?

[Altera_Forum]

can I connect cycloneIII's GNDA with digital ground(GND)?  

ps:GNDA is analog GND of PLLs.   Thank you for your reply~

[Altera_Forum]

Altera recommends: "The designer should connect these pins to an isolated analog ground plane on the board." But, to be honest, I do not know of many boards that have been built according to this rule. Often, a single ground plane is used and this works. Personally I recommend paying attention to the negative pads in the ground plane caused by signal vias. If these negative pads are too large then the remaining track width is small what causes inductance. The effect of this is worse that that one caused by a common GND net.

[Altera_Forum]

The said isolated analog ground recommendation can be found e. g. in cyclone iii device family pin connection guidelines. AN466 - Cyclone III Design Guidelines tells in contrast 

--- Quote Start ---  GNDA and GND pins should be connected to the same ground plane as the device’s digital ground.  --- Quote End ---    It seems to me, that the first recommendation is continuing an outdated concept found in some previous Altera design guides. More generally, I think that the concept of separated analog ground planes has shown inadequate in many mixed signal designs even with parts as high speed ADC, for various reasons. To mention just one serious problem: It tends to cause nasty ground differential noise voltages already at moderate distances (e. g. 1") from the common ground location. If more than one mixed signal device is connected to both planes, it's advantages are questionable. It looks good in data sheets and application notes dealing with a single device.  There have been other recommendations in the past, e. g. to have ferrites or decoupling resistors in both the VCCA and GNDA supply and a capacitor across the pins. With Cyclone III, the problem addressed with these measures - noise susceptibility of VCO supply - has become less dramatic due to the internal voltage regulators. Thus I think the AN466 guideline quoted above is more appropriate.