Electronic – Eagle: keep decoupling caps near their IC


Is there a way to annotate decoupling caps in the Eagle PCB schematic, such that in board layout, the airwires (or some other thing) make it clear which IC it's 'supposed to be near'? Right now the airwires just give me a line of caps all between supply and ground, so I have to work out which cap is for which IC.

Of course they are mostly the same value caps, and I could figure this out with naming. But if I had a device with many supplies and lots of decoupling needed, it seems like this would be a pain, so I'm wondering if there is some smarter way to do this.

Best Answer

As far as I'm aware, Eagle does not have this function. Two suggestions:

  • Place the capacitors explicitly on the IC's power pins, rather than on a separate power net. This can make your schematic quite cluttered.
  • On the schematic, place a box around the IC and the associated capacitors.

Neither will prevent you from placing them far away but do make the intent clearer, which is ultimately the goal of a good schematic.

Altium Designer has the concept of Rooms, which allows you to create a group of components that are associated but independent - this is probably the closest to what you want.

One final suggestion: for each IC, place a jumper from the global supply to an individual power net. This would allow you to have separate power nets for each IC that would stay attached. This might complicate ERC, and would introduce an extra footprint (although you could make this footprint a testpoint for a DFT bonus!).