Creating the Perfect Part (2/4)

Part 2 – Schematic Symbols

If you need to use a component that’s not in your library, what two things do you need to consider while designing it in your CAD tool?

  • How to make your part design accurate and practical for manufacturing
  • How to make your part reusable in the future

The second part aspect that requires perfection, and the focus of part 2 of our series, is the schematic symbol which is a logical (non-physical) representation of the part that emphasizes readability for the design engineer’s schematic.

Schematic Symbol

The main goal in designing the schematic symbol is to preserve clarity of the overall schematic, and to make your representation of the part helpful in accomplishing that.

1) Consider breaking up a part into multiple symbols, like a dual op-amp.

perfect-part-2-dualopamp

 

2) For ICs, their schematic symbol (typically a square) should be as large as necessary to be readable.

Like this!

perfect-part-2-readable

 

Not Like This…     

perfect-part-2-notreadable

 

3) It is better to avoid using pins on the top or bottom of the symbol, and that a left-to-right flow should be preserved (inputs on the left, outputs on the right).

Like this!

perfect-part-2-sidepins

 

Not Like this….

perfect-part-2-incorrectpins

 

4) Pins should be named in such a way that they indicate their function and uppercase letters should be used.

5) For clarity, all of the chip’s pins should be shown.  Pins that are unused should still be shown, but marked as such on the schematic (typically with a no-connect flag that looks like the letter ‘X’).  The thermal pad should have a pin on the symbol and should be connected to ground in the schematic.

This Arduino Micro, for example.

perfect-part-2-arduino-micro

 

Consult Upverter’s style guide (here) for more suggestions on how to keep your schematic symbols and nets clear and readable.

For the practical “How-To” of creating the schematic symbol of a new component in Upverter, see our YouTube video.

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