How do you deal with unused pins on schematic symbols when the symbol is only electrically connected to fewer pins than the physical device or footprint has? Some of the more difficult parts to configure are devices that electrically connect like the TO220 , a 3 leaded device with a electrically connected heat sink 'TAB'. Do you treat it as a pin? How do you show it on the schematic?
I have seen folks stack the pins one on top of the other to force a 'connect dot' on the schematic to graphically look like a 3 pin device but actually connect the tab to the center pin. Other devices like diodes that are packaged in SOT-23 packages can only use 2 out of the 3 available pins, but the schematic symbol for a diode is a 2 pin device, which may be connected between pin 1 and pin 3 of the SOT-23. It might be convenient to run a trace through the unconnected lead on the SOT-23 (pin 2) for layout sake, but it will generate an error on your board when you run DRC... Any sharp designers out there have a tip or trick for dealing with these or other scenarios? Bill Brooks PCB Design Engineer , C.I.D., C.I.I. Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/[EMAIL PROTECTED] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
