How to get from SN74AVC8T245 to SN74LVC4245A?

There is a library item for SN74AVC8T245. But its supply voltages do not suit into my application. SN74LVC4245A is what I want. Schema symbol and PCB footprints are same, only name changes. What are all the places I need to go to make the change.

If there already is a SN74LVC4245A part somewhere, then where is it?

Both are 8 bit level shifters if you want to know.

Just save as the new name and make the changes that you need. It will probably give you what you want.

In my way of using KiCad it would need:

  • add alias to that symbol with name of new IC,
  • delete previous symbol at schematic and place here the new one,
  • update PCB from schematic.

The 8T245 does not have hidden power pins, so it is trivial to open it in the editor, rename and save in your own private library

Very good. Looks like an easy thing to do. And it should be easy to continue with the board. I can’t run Kicad now, but surely somewhere there is an option to update the bill of material, too.

If you start with modifying Schematic symbols, you should know a bit about library management.

KiCad’s default libraries are read-only because they are a part of KiCad and can be updated / changed with KiCad updates, and then you would loose your changes if you modified them.

So in short, the order to do things is:

  1. Open the KiCad Project Manager.
  2. Open the Schematic Symbol editor.
  3. Symbol Editor / File / New Library
  4. Enter a filename. Make it a “Project Specific Library” (for starters).
  5. Browse to an already existing symbol, right click on it and Save a Copy as.
  6. Click on your newly created library name.
  7. Double click on the fresh copy in your new library to load it in the editor.

For a more formal and complete tutorial about library management, have a look at:

The FAQ part of this forum has quite a lot detailed tutorials about different parts of KiCad.

Thank you all. I have now a created a project specific library. I’ll now check BOM part, that is, ordering info for the assembly house.

I think I found the library entry and modified it. The BOM will tell how good it is, but this is good enough for now.
Edit: One note: SN74AVC8T245 has three ground and power supply pins, 6 total. The symbol shows 3 power supply pins and one ground. PCB footprint has them all.

Are all pads in the PCB connected to a net? If so, then your schematic symbol likely has “stacked pins” which are normally set to “invisible”.

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