Honored Contributor
Honored ContributorWhen I have been in this situation with a BGA device, I tie the 6 I/O pins to VCCINT through resistors. This requires that you "borrow" a via from an I/O pad next to the via that needs to be tied to VCCINT, and that you use an 0402 resistor to short the vias together. This placement is really no different than the placement for the decoupling capacitors.
Its a little easier to show what I mean with a photo ... scroll down to the photo in Post#9 http://www.alteraforum.com/forum/showthread.php?t=44695 Click on the photo to enlarge it. The blue 0402 components are resistors, while the brown components are decoupling caps. Faced with a situation where I needed to optionally tie 6 I/O pads to VCCINT, I would give up 12 I/O pads, and "steal" 6 of the BGA breakout vias to tie them to VCCINT (the trace on the top-side of the board to the BGA ball pad would be cut). The PCB assembly BOM would then include the 6 VCCINT shorting resistors if I loaded the BGA device that needed those VCCINT pins. If you're not quite sure what I am talking about, you can download the PCB design files (Allegro) and take a look at them (there is a free viewer). I don't recall if this specific design needed the VCCINT migration option, but this method would meet your needs. Cheers, Dave
