A lot of parts have external pads that are connected internally–e.g. the Omron tactile switches, and voltage regulators with a tab.
Any idea on how to get Eagle to understand this? It won’t let you connect the same “pin” on a symbol to multiple pads on the footprint, which is a PITA for routing and for SMD regulators that want to have the heatsink pad grounded.
Create the schematic symbol with a pin for each pad or tab on the footprint.
That’s a common approach that I’ve seen, but not very satisfactory. It creates two independent signals, which Eagle expects you to connect via a trace. That’s fine for cases when, for example, a chip has multiple grounds that have to be connected externally.
However, when the pins are connected internally, it creates bogus airwires and clutters the schematic with package details. The bogus airwires negate the benefit of the internal connection when routing traces. It’s a nuisance when laying out something like a keypad, where the switch can act as a jumper/pair of vias.
In the case of a live heatsink or thermal pad, e.g. a TO-3, a TO-220, or the like, the details of the extra “pins” will vary between packages, which makes setting up a library more difficult. For example, a footprint for a horizontally mounted TO-220 that recognizes the tab as a live connection can’t be used on the same device as a vertical TO-220 footprint where the tab isn’t on the board.
I’m creating a custom part in a new library and I’d also like to find out how to connect pads/pins internally.
For instance, on the AOP610, pin 7 = pin 8, and pin 5 = pin 6. I’ve made the 8 pin DIP package, but I want these pins to be equivalent for my custom part. Can Eagle CAD do this?
The best compromise I’ve found is to add another pin to the symbol with a similar name to the equivalent pin I want to connect it to. Then change the swaplevel for both pins to a non-zero value. All pins of the same type and the same swaplevel can be swapped with the “pinswap” button.
I just connected the two pins in the schematic anyway because the pins are side by side. This could be a problem if the pins to be connected are the base of a TO220 transistor and the metal tab, as the board traces might get in the way and complicate your board layout.
If anyone comes up with something better, I’d love to know what it is.