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07-17-2009 10:14 AM
I have an LXT V5 where the AVCCPLL is 1.2V. It's not clear to me from UG196 whether or not each voltage needs its own regulator -- particularly since at least one of the evaluation boards (ML50x) shares one regulator for MGTAVTTTX, MGTAVTTRX, and MGTAVTTRXC. For clarity, can I supply all 1.2V pins (MGTAVCCPLL, MGTAVTTTX, MGTAVTTRX, and MGTAVTTRXC) from a single regulator as long as I meet the three requirements in wissolik's posting?
07-17-2009 11:06 AM
07-18-2009 03:57 AM
The fundamental 'problem' is,
the serial links are all but impossible to debug.
you use one regulator and filtering, what do you do if the link does not work or even worse it 'tempramental'.
Now this could be 1001 reasons, it could well be noise on the MGT power lines, they are very suseotable to noise.
You end up like me with no finger nails in very short time.
It's because of this, and only this, that every one I know is VERY conservative with the power supply to the MGT.
Having said that, I've used switchers and filtering and it works very well, first time,
but be carefull, and if you have the space / power / money, design conservativly.
04-23-2010 12:57 PM
we are using GTP power in a Virtex-5 FPGA.
--ug196.pdf case 1 (page 231)------
MGTAVTTTX = 1.2V
MGTAVTTRX = 1.2V
MGTAVCCPLL = 1.2V
MGTAVCC = 1.0V
MGTAVTTRXC = 1.2V
I'am miss take. a MGTAVTTRXC pin is not connected ("MGTAVTTRXC"= floating.)
How can I fix this? (hardware not Adjustment)
04-24-2010 09:21 AM
Do I understand you have a floating power supply pin,
Well, your going to have to modify the board to add the power I'm afraid, else the chip is going to be out of specification,
04-24-2010 09:29 AM
Do you have a floating power supply ball? If you have vias on all of the ball pads, and if your vias come all the way through the printed circuit board, then you can try adding a power connection to the via for the floating ball. Otherwise you'll have to try something more complicated like modifying the top of the board with the FPGA off, or drilling the board from the back side to get to the floating ball, etc.
Best of luck,