Same Value for Multiple Components


I am new to kidcad and am trying to use an old schematic to see if I can recreate it and hone my kicad skills. There are multiple parts with the same value, but different references and pin layouts. For example, they all share the value “LFE3” and have references of (U1-1, U1-2, etc). I don’t quite understand what is going on.


The reference field is used as the unique identifier of a component in this project.
In kicad it needs to end in a number. (letters are used to identify the unit of a multi unit symbol)
Typically the reference starts with a standardized letter that identifies the product group (R for a resistor, U or IC for a complex part, …) See:

The footprint field connects the symbol to the footprint (landing pattern). So it tells you how that component physically looks like.

The value field can be used for whatever you want it do be used. It is meant to hold identifying information of a part. For a resistor this will be the resistance value. For an IC it will be the manufacturer part number. (or a short form of it.)

You can also add user fields if you need to include more information. (examples that come to mind are: Fields for manufacturer part number, house part number, ordering information, …)

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My first thought was for example an IC such as a 7400 NAND gate where multiple schematic symbols are part of the same Footprint ( = PCB package with mountingholes etc). But these are called U1A, U1B, U1C, U1D.

If you still want to know more it might help to post a screenshot of the schematic, or the whole schematic.

I’m not sure what the part is, but I did to a search on “LFE3” and the first hit is the following part (at DigiKey): Lattice Semiconductor Corporation LFE3-70EA-7FN672I. This is a 672 pin BGA. My guess is the schematic that you are copying isn’t from KiCad, and each of the U1-# symbols are different parts (or gates) of the same chip. In KiCad they would be numbered U1A, U1B, etc.

There is a thread here that I saw linked recently about drawing multiple different shaped gates for a component, but I didn’t just now see it in the FAQ area. Hopefully someone else has that link on their fingertips that can post it here to give you a guide on drawing all the different gates for that huge pinout chip. (If that really is the part in question.)

I found the link to the thread. Here you go: IC footprint VCC+GND. (This tutorial isn’t for your exact use-case, but should be close enough to understand the steps required.)

Here is an example of two of the instances in the schematic that was made in Cadence/Allegro.

So you have a pretty big BGA.
All the pins of the BGA are not going to fit in a small rectangular schematic symbol.
Therefore the schematic symbol is divided into sub symbols.
“U1” is the RefDes of your IC. It will be the name of the physical part in PCBnew.
The “-3” and “-7” are suffixes to be able to keep the different parts of the symbol apart.
“PL21A” is a name of a pin, usually it is a logical description of what that pin does.
“B1” is the pin number of the BGA Package. Column B, Row 1 just like a checkerboard.
“DA4P” is a label. It is the net name of the wire, which will also be used in PCBnew.
In KiCad this is usually done with “hierarchical labels”.
“SH7” is probably sheet 7. A reference (loose text?) to where the wire goes to.

In your other (similar) thread I posted a link to KiPart, Youtube vid of a Python script to help with creating such large symbols.

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