Here you are: you’ve upgraded your PCB design software to Altium Designer after four years working in OrCAD. It’s an exciting change and one that will surely give you challenges while you are in your training process trying to learn the capabilities of all the tools offered in this unified design environment. You might find yourself resorting to old processes out of reflex only to discover that there’s a much more streamlined variant available.
But wait—there’s an important step you need to get past before you jump into learning all the ropes: how do you create a schematic? You might feel overwhelmed with all of the features, but don’t worry! Whether you’ve got decades of experience in your pockets, or you’re starting out fresh in your design or engineering careers, every Altium designer before you have had to do this exact first process.
Breaking down the software into baby steps allows us to bite off just the right amount to chew on. With the end goal often to produce a full working PCB, we can then start with the first step of creating a schematic to base our PCB off of.
How to Create a Schematic with a Simple Audio Amplifier
I am a sucker for audio circuitry. I’ve built a handful of speakers with previously manufactured PCBs, however, I’ve never actually built one myself. So for this first PCB, I wanted to produce a full working audio amp that I could put right in my next project.
I’ve chosen to base this work on a very simple amp using the LM386. It has minimal components which makes it a great first step to work off. Especially for a first schematic, the best choices for acclimation to tools and features will always be something which is minimal and with ample space to add to along the way.
To give you a picture of what we’ll end up with, below is the end amp schematic we’re going to work through:
Schematic of a full, simple audio amplifier in Altium Designer
Opening a New Schematic
The first step with any project, after you grab your coffee and do your morning stretches, of course, will be to open a new PCB project. All you have to do here is head to File > New > Project > PCB Project.
Once opened up, we’ll create a new schematic sheet to place our components. Right-click on the new PCB Project created and navigate to Add New to Project > Schematic.
This will give us our blank canvas to base the schematic off of. Look at you go—I’d say it’s time for a five-minute break.
Adding Component Libraries
We have already gone over how to add component libraries into Altium to give us any component to place on schematics. Since we’ll be using a common LM386 op amp, we’ll add the Texas Instruments Amplifiers and Linear Special Functions library.
Make sure you’re comfortable with this process or at least have that blog favorited as you’ll want to make sure you can make use of all the component libraries that Altium has made available for you in your future designs.
Square One: Adding the Central Component
Now that you’ve had your break, maybe a coffee refill, and you’ve updated your component libraries, it is time to start drafting in your schematic. I always like to start with placing the initial ICs that we’ll be basing circuits off of. In this case, we’ll start by placing the LM386 right smack dab in the middle of our page.
Querying the LM386 in the libraries search bar, we will find a few options. I simply selected the first part (LM386M-1) as a starting part. We can slightly edit these component’s names as we go along.
Simply click and drag the IC into the schematic page to place it. You’ll end up with something that looks like this:
Near empty schematic in Altium Designer populated by an IC
You might have different ways to begin your designs, or a more individualized design process for placing components on the schematic, however, I always love to have a central part to place the reference components around.
Editing the Values of Each Component
As you may have noticed, my IC part number (LM386) and designator (U1) is slightly different from the specified name given from the library. I removed the end ‘M-1’ as to keep the IC more generic for our purposes as we may need a different mounting method depending on the end PCB we have in mind.
To edit the values of the IC, simply double click on the value you’d like to edit. The search bar on the right will prompt us for a value to enter:
Schematic with central IC component showing component properties
Once we’ve entered the appropriate part number and designator, we can move on to place other components.
Placing Reference Components in Your Schematic
Similar to the first step, we’ll be searching the library database for our basic reference components (caps, resistors, battery sources, speakers) to place around the IC which will nearly complete the required schematic.
Instead of searching through the Texas Instruments library, however, I simply used the Miscellaneous Devices library to find components to start with. Remembering again that we can change each value as we go along we can select base components so that later we can edit them to our desired value.
The important takeaway, though, is to label and change the values of your components accordingly with your design needs and to document necessary communication. For the purposes of this amp design, the end component placement will look like the following image:
Schematic now populated with necessary components
After we’ve got all the components on the board, we can begin to connect them to their appropriate neighbors.
Adding a Port for an Audio Input Source
Of course, in many of your designs assuredly you will have to place something for reference. For the purpose of this amp, I need to note where the audio input will come from. Instead of trying to leave a bunch of sticky notes on where to place the audio input, I simply add a port to the schematic to give us this info which we can manipulate later on.
If you’re looking to place a port, for reference or necessity, navigate to the upper toolbar and select ‘Place Port’ to place this reference onto our schematic in the same fashion as a component.
You can change the text to whatever you’d like but I’d recommend if you’re writing yourself a less serious note in the port tag, make sure to change it before you ship the schematic out to your team. An example of the added port can be seen below:
Schematic noting the reference port placed on left-hand side
Placing Grounds Within Your Schematic
Next up in my design flow is adding the grounds for my design. No circuit is complete without them, after all, and this seems like as good a time as any.
Similar to placing the port to our diagram, we’ll navigate to the upper toolbar and select GND Power Port. We’ll then go around placing necessary grounds to the specified pins on our circuit. Make sure to follow the necessary grounding best practices, but other than that, adding grounds really is just as easy, Altium makes sure that these important steps in the schematic process are intuitive.
If the real estate is a little tight, simply place it away from the pin as we’ll be able to wire them together in the next step. After you’re done, your board should look something like what’s found below:
Added grounds on schematic attached to necessary components
Keep Your Wires Clean
You’ve almost finished the beginning steps to making a schematic. But before you take your next break, you’ll need to work on your design’s wiring. To connect each component to its correct counterpart navigate to the upper toolbar and select the ‘Place Wire’ tool.
From here, all you need to do is click the pin where you need to start the wire, then the pin to end the wire. In this particular example, since we’re working on a pre-established design and therefore know which components need to go where, the wiring should be straightforward.
If you’ve been following along, or if you’ve been working from your own simple design, your schematic should either have the same features to it or look similar to this:
Schematic with central IC component showing component properties
If you can believe it, you’ve just created your very first schematic with Altium Designer! Give yourself a pat on the back since you’ve taken the first step towards PCB greatness. Save it all up under any name you’d like and then prepare for the next steps toward creating the physical PCB layout.
While this is a very basic example of what the Altium schematic capture is capable of, there are a plethora of further online resources for utilizing the schematic capture tool to its optimized efficiency such as:
- Altium Schematic Documentation
- Schematic Placement and Editing Techniques
- Creating Connectivity
- Design Reuse with Managed Schematic Sheets
If you are looking to expand your knowledge even further, check out the great online resources, or talk to an Altium expert today.
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PCB Design Tools for Electronics Design and DFM. Information for EDA Leaders.More Content by Altium Designer