leaving PLL power supplies unconnected

[Altera_Forum]

I use a Cyclone II in a design which does not use any PLL at all. I'm very concerned about power consumption and since PLL consume "a lot" for me, I wonder if it possible to use the chip without powering PLL_VCCA and PLL_VCCD. 

Made simply, the datasheet says NO.  Anyway, anyone ever tried this before ? :rolleyes:   Warm regards.

[Altera_Forum]

I have never done this before but I would be worried about doing it. I would be concerned about how this would affect the POR circuit since this circuit usually waits for all voltages to be valid before it releases the part from reset. That is the only yjong I can think of off the top of my head but there could be some other reason. 

 It would be very cool if you could leave these unconnected since it could save some power. Based on your design have you esitimated the savings that could be realized by not powering the PLLs?

[Altera_Forum]

A thread exists on this topic. You must connect power even if you don't want to use the PLL. As long as PLL doesn't drive a global net in your design, it should not consume much power. 

 http://www.alteraforum.com/forum/showthread.php?t=70&highlight=pll+power

[Altera_Forum]

Do not leave PLLs un-powered. It can cause high current consumption.