Decoupling cap placement
What is the correct way of placing decoupling capacitors?


Rule 1 - as close to the chip's pins as physically possible.

Rule 2 - Keep ground plane vias from the decoupling cap pins as close as possible and, if necessary on heavy duty current pins, use several vias.

I'm not too worried that the power feeds the "other" end of the pin providing rule 1/2 is observed and there is nothing in the chip's data sheet that says otherwise. Sometimes it's physically impossible to have power plane vias on the outside of the chip's pin.

Rule 3 - do what the data sheet suggests (or better)

Rule 4 - use the most appropriate type of capacitor and take note of the self-resonant frequency of some capacitor types (making them inappropriate).


  is it ok to occasionally route other voltages over the power plane?


Sure but try not to do this too much on the ground plane.