My dad grew up in a time where it was difficult for hime and his brothers to purchase new hardware for the various projects that they busied themselves with, so they became masters in the art of reuse. Wheels that had been liberated from a rusty wagon wound up on a homemade go-kart, while an old rebuilt lawn mower engine provided the power. Once the go-kart had been run into the ground, some parts were repurposed for one project while the engine was coupled with a giant propeller for experiments in wind power.
If you’re thinking that this all sounds kind of risky, I would have to agree with you. But dad loved telling us these boyhood stories, and it birthed in me the same desire to find new ways of reusing work that I’ve already done.
For the longest time though, PCB designers weren’t able to leverage this reuse methodology in their designs. Not only would we have to recreate the same shapes and models over and over again, but larger pieces such as schematic pages and portions of the layout would have to be tediously recreated for each design.
This has changed though as PCB design tools upgrade with more and more design reuse capabilities. If you aren’t already looking at engineering productivity and design reuse tools to reduce your design cycle times, you may be missing out on a real gold mine. Here are some reuse ideas that could be very helpful if you haven’t considered them before.
What is Engineering Productivity and Design Reuse?
Design reuse is the practice of using portions of previously completed designs and reusing them in a new design. This can happen in many ways and one of the most common is when a page of schematic circuitry is read into a new flat schematic design.
This can involve some work to resolve net name and reference designator conflicts but is a tried and true method. A step beyond that would be to use a block symbol to link to another schematic page. This is called hierarchical design, but we’ll talk more about advanced schematic and layout reuse in a moment.
Design reuse is much more common than you may realize, in fact you’ve been using it for as long as PCB design tools have been around even if it wasn’t officially labeled as design reuse. Every time you instantiate a library part into your design, you are using design reuse. There is one copy of that library part either in a library, and yet you are repeating that part all over your design.
Additionally every time you copy and paste circuitry or data into your design, or are executing some sort of script that creates parts or circuitry you are essentially doing design reuse. Even manually copying a schematic sheet into the design database is design reuse, so pat yourself on the back - you are already in the midst of design reuse.
PCB layouts like this can benefit greatly from design reuse techniques
Design Reuse in Your PCB Design
As we mentioned earlier when you link a block part to a schematic sheet you are working with hierarchical design reuse. This allows you to store off those “blocks” of schematic sheets in a library for future reuse whenever you need them. Your PCB design schematic capture tools will handle renaming nets and reference designators so that there aren’t any conflicts, and you can easily place the block symbol on the top level schematic page.
From there you can copy those blocks to duplicate their schematic circuitry. This is especially useful for designs of multiple channels of the same circuitry that need to be exactly repeated. You don’t need to create 8 schematic sheets for 8 channels, you just need to create one block of circuitry and copy the block into 8 individual blocks. Your schematic tools will again handle renaming the conflicts, and you will be much more productive.
Schematic circuitry isn’t the only thing that you can reuse, however. Another great aspect of reuse is to pull in your complex design rules for both the schematic and the layout from a saved location. Once in your new design, you can modify them as needed, but you’ve started with a good template that will save you time and effort.
Design reuse is also used often in layout to recreate areas of component placement and routing. Just as in the schematic, these sections can be either pulled from existing designs or saved as their own entities in libraries. And lastly, pulling in previously configured manufacturing output file commands will save you the time of having to recreate your output scripts every time you are ready to tape-out another design. Like the design rules, you simply pull in a template and then modify it for your needs.
OrCAD’s powerful schematic tools allow you to access your hierarchical blocks from the top level schematic
What you Can Expect from Design Reuse
Design reuse is going to save you a lot of effort and the time it would take you to recreate all of that work every time you need it. You will find that design reuse is a fantastic way to get your product designed, built, and sent out for manufacturing faster using known, good circuitry. Most PCB design tools today have different types of design reuse technology built into them, and you should see exactly what you’ve got available to you to start realizing the benefits of design reuse today.
The PCB design tools from Cadence has some of the most advanced design reuse features that you will find incorporated into it. OrCAD OrCAD PCB Designer has schematic hierarchical design capabilities as well as managed reuse layout modules just as we have been describing. You will also be able to pull in design rules and constraints as well as other design data that you can easily modify for design reuse. With OrCAD you will be fully equipped to start using design reuse processes that will help you to become more productive as well as to help you minimize design errors.
If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.
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