IPC-7351 gives a pin out and a 0 degree rotation for SOT23-3 packages; but, IC vendors use many different pin numberings.
When I make my library component should I use the IPC pin numbering for all of my parts or use the datasheet pin numbering for each part?
I can put functional labels and put the part body outline in the schematic symbol to reduce confusion there.
I am most concerned about confusion at the board assembly house. It seems to me that they would prefer consistent IPC numbering and rotation. But they might look at the datasheet or some other info from the manufacturer resulting in confusion.
Best Answer
You ALWAYS use the manufacturer's data sheet. If it differs from the industry standard 'pin 1 in the top left corner, next to the index mark, increasing anti-clockwise round the package', then put a warning note on the schematic in text.
But first, does the part really have a non-standard pinning? Have you read the data sheet correctly? Have you confused a pins-up with a pins-down drawing? Has the data sheet been published with an error (it can happen). Check the pinning of some pin-compatible parts from other manufacturers, or contact the manufacturer. Once you are sure what the data sheet says, use that. I have had 'function' compatible parts that would work on the same footprint, with different pin numbers from different manufacturers, that required a table on the schematic to avoid confusing myself as well as others.
As in everything in life, the specific (data sheet) always supercedes the general (the standard).