What Good Schematic Design Looks Like

A few industry standard schematic tips will lay a good foundation for your circuit board and are very important for a couple of reasons. The first of these are “details”. If you miss a single detail during any portion of a printed circuit board design you’ll pay for it on the back end. If your schematic is layed out such that you can find and fix these errors you’ll save yourself hours of time not to mention hundreds or thousands of dollars.

Second, once you reach the pcb layout phase of your design your schematic will be the goto document for planning how your circuit board is layed out. Having a schematic that is layed out logically with respect to pcb design will again save you hours of time.

Below you’ll find several tips for capturing a schematic. These are tips that are more or less industry standard and expected when an engineer picks up a schematic to review a design or begin troubleshooting. Also you’ll find below a reference design of a 32 page schematic which will actually shows you what a schematic looks like that has been captured properly.

Schematic Tips

  • Flows Left to Right: The most important fundamental of a well designed schematic is that it flows from left to right. Inputs to the left and outputs on the right. It’s just like reading a book and any seasoned electrical engineer or will expect to see the followed for nearly every single situation.
  • Signal Naming: There are lots of different ways to name your I/O but the point is really to just be consistent. All uppercase, all lowercase it really doesn’t matter, but it needs to be consistent throughout the design. Using underscores between words (+5VDC_POWER_STATUS) well ensure you don’t have any issues when importing / exporting your netlist between pcb design software. It’s also a really good idea to note active low signals with a “_N”. This way when you’re debugging the circuit you won’t have to reference the component datasheet.
  • No 4-way Ties: A 4-way tie is nothing more than where 4 nets all terminate at the same point. If you accidentally form a 4-way tie the DRC (design rule checker) won’t throw an error, but when someone reviews your schematic they might miss the little circle that informs them that the 2 intersecting lines are actually connected. Avoid 4-way ties and your life will just be easier in the long run.
  • Organization: Learning how to organize your schematic will get easier with time. When glancing at your schematic it should be simple to see what is going on. If it’s not, you need to reorganize. It becomes especially difficult to organize your schematic when you’re laying down several of the same circuit. With time you’ll learn just the right way to arrange the components in the least amount of space. It will truly be a thing of beauty.
  • Adequate Notes: If there is something done for a specific reason, or you need a certain trace a certain width for current carrying capacity its always always always a good idea to make a quick note of it on the schematic. It will remind you weeks or months later why you did, what you did. It will also inform any pcb design engineer exactly what he needs to specify for layer placement or trace widths.

The following reference schematic has been completed by the nice folks at Altera. It’s a 32 page schematic for an Altera Development Kit. This schematic exemplifies all the schematic tips and is a guide to review if you ever have questions in the middle of your own schematic capture project. Download Now.