New Altium users may not fully understand the benefits of organizing schematic sheets into a hierarchical top-down or bottom-up perspective designs. As a result, users often proceed with simple (flat) schematic designs without giving a second thought to project organization. This approach can often lead to a disconnected schematic design process, especially in multi-sheet designs where net connectivity has to be maintained across multiple schematics.
A hierarchical design within Altium can be defined as a design where the sheet-to-sheet relationships (the structure) in the design is represented, with sheet symbols representing the lower sheets in the design hierarchy. The symbol represents the sheet below, and the sheet entries in it represent/connect to the ports on the sheet.
In Altium, starting a hierarchical design requires the creation of sheet symbols. A hierarchical sheet symbol is an electrical primitive, used in design reuse to represent a sub or child sheet in a hierarchical PCB design schematic. Sheet symbols also include sheet entries, which provide a net connection between parent and child schematic entry sheets, similar to the way that ports provide connections between schematics in a flat-sheet design. The sheet symbols can be used to organize multiple schematics on a large design and provides users with the overall flexibility to schematic view net connections across their entire project.
In the image below, the sheet symbol is defined by an orcad schematic capture designator. This can be used to set the category of the design, with its respective design file name linked to a particular printed board schematic sheet. When defining the entries in the sheet symbol, the sheet entry names are then linked to the same name in their sub sheets.
In a hierarchical design composed of multiple sheet symbols, each with its own respective design entry, it’s very easy to navigate to a particular sheet of the project by using Ctrl + double clicking on a sheet entry. This will focus on a particular net-named port on its respective sheet and allows users to view its connection.
In a multi-sheet design, it may be difficult to schematic view connectivity and show the project viewer the overall design structure. That’s why it’s extremely beneficial to use sheet entries to define a hierarchical structure. This will allow project users to save time to eliminate the headaches associated with multi-sheet design, as they proceed to design review for production.
Check out Altium in action...
Hierarchical & Multi-Channel Design