SOT223; Joining pad to tab

Question

Hi folks.

I'm having a problem with using the tab on SOT223 voltage regulators that use the tab as a heatsink and is usually the same connection as the centre pin. But when I add a polygon around it to increase the surface area, it either leaves the centre pin disconnected or the tab is isolated.

Is there a nice way to achieve this?

Thank you.

dougw · Answer

You are right, the schematic symbol should have a pin for each pin on the device. You can edit the device to add the pin. You could check the 78L05F device in the Linear library to see how they did it there in the SOT89, but note they connected the 2 pins in the device package. The LD117AS12TR device in the V-Reg library has an unconnected pad, you can just add a pin to the symbol and connect it in the device window, or create a new symbol with 4 pins.