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Introduction to Hierarchical Schematic Design


  In this post we’ll give a quick introduction to hierarchical schematic design, what it is, and how it can help you better organize your projects.

The problem with flat schematics

If you’ve ever worked on a PCB design team before, chances are you’ve used the flat schematic approach before, even if nobody called it that. In a flat schematic, each major component of a design gets its own page, that can later be integrated into a file system or imported into a master schematic representative of the whole design.

Flat schematics are fine when your hardware designs can be captured in one or two pages, but as your projects grow larger and work gets distributed among more designers, you’re bound to run into a few problems:

  • Typos and errors, especially in the net names, can result in duplicate nets or unintentional shorts in the final design.

  • Circuits must be replicated across pages by manually copying, pasting, and renaming labels—all of which can be error prone.

  • Engineering change orders can be time consuming, requiring an engineer to manually scrub all pages for additional changes.  

While the components contain references to each other in the form of net names and callouts, the pages themselves are static—no software links one page to another, and the engineer must manually navigate the pages of the schematic to understand the whole design.

And so it was that the stage was set for the appearance of a new PCB design paradigm: hierarchical schematic design.

What is hierarchical schematic design?

Hierarchical schematic design is a better way to organize your PCB designs. In the hierarchical approach, you have a main design or top sheet, that contains block symbols representing all the subcomponents of your design. Each subcomponent in turn can be blown up to reveal additional sheets each with their own block symbols.

The nested structure allows a designer to move from sheet to sheet, creating new blocks for new components, and reusing old blocks where necessary, greatly improving PCB designer productivity. The schematic editor takes care of any data conflicts automatically, making it easier to manage net names, avoid conflicts, and make changes.

Hierarchical schematics help you make the most of modern PCB design software

PCB design software has come a long way in recent years, making it easier to hold all the information regarding the assembly and fabrication of a PCB in a single CAD file. Cadence PCB design tools support hierarchical schematics. Why let that comprehensive interconnectivity go to waste?

A hierarchical schematic gives you a birds eye view of your design, allowing you to dive into each functional area by following each block symbol on the topsheet. Together these technologies make a PCB designer’s life easier.