I'm trying to fix a clock problem on a freebie board I got. It drives an expensive display, so it's worth fixing. It appears to be a 4-layer board with signals on the outside and +5/GND inside. +5 comes from a header along one edge that connects to a fairly long wire back to a SMPS. There's a CY7B992 programmable skew clock buffer in PC32 (datasheet link below) on the board in one corner. It's powered by the +5V plane. When the embedded PC that connects to this board works hard, the clock out of that chip has problems which manifest as display glitches. I suspect that the 5V quality is not up to snuff near that clock buffer (I had assumed it was powered by the adjacent 3.3V regulator when I first examined the board, but it's not).
I can make a new 5V from the 12V. I'm looking for ideas on how best to rework the board to change the supply. The pins seem to be supplied by vias under the chip, with caps connected by the pins. The chip has two sets of power pins, Vccq for the internals, and Vccn for the outputs. I'm guessing I only need to change the 2 Vccq pins over to the new supply. I can probably cut the legs to isolate them, but if necessary I could also remove the entire chip with hot air and cut the traces. If I dead- bug a 5V regulator on top of this chip, will I be able to adequately bypass the new supply, or will I just create a new power problem? Is it important to change the Vccn as well?