Altium Designer Helps You Track Reference Designators on Your PCB

 

Introduction

When designing printed circuit boards (PCBs) in Altium Designer, it's important to track reference designators to ensure proper connectivity between components. A reference designator is a name given to a component on a schematic diagram that allows it to be uniquely identified and linked to its corresponding PCB footprint. Altium Designer has powerful features to help designers manage and track reference designators throughout the design process.

In this article, we'll explore the reference designator tracking capabilities in Altium Designer and how they can help you:

• Avoid duplicate designators on schematics
• Synchronize designators between schematics and PCB
• Cross probe between schematics and PCB
• Highlight net connections
• Identify connectivity issues

We'll also provide tips and best practices for working with reference designators in your designs. With Altium's robust tools for tracking designators, you can have confidence that your components are properly connected as you take a design from schematic to layout.

Avoid Duplicating Reference Designators

When first placing components on a schematic, it can be easy to accidentally give two components the same reference designator. This will cause major issues down the line as Altium will not be able to distinguish between the two components.

Fortunately, Altium has features to avoid duplicating reference designators. When placing components, the designator will automatically increment based on the designator prefix to ensure each one is unique.

You can also configure default designator prefixes based on component type in the Document Options for the schematic:

Setting unique prefixes for different component types makes it easy to identify components at a glance on busy schematics.

Altium also has a tool to check for duplicate designators. To access it, run the Electrical Rules Check (ERC) on the schematic. This will scan the schematic for errors and display notifications in the Messages panel:

The Messages panel will call out any duplicate designators, allowing you to resolve the issue before moving forward with the design. Running the ERC periodically allows you to check your work as you assemble the schematic.

Synchronize Designators Between Schematic and PCB

A key advantage of Altium is the ability to synchronize reference designators between the schematic and PCB layout. This ensures the designators match on both sheets for easy cross probing.

Synchronization occurs through Altium's automated annotation process. After laying out the board, you can run the Annotation tool. This will push designator changes from the schematic to the PCB, updating the footprints to match.

For example, if a designator on the schematic changes from R1 to R2, running Annotation will update the PCB footprint automatically. This prevents you from having to manually change designators between tools.

Annotation also works in the reverse direction - changes on the PCB can sync back to the schematic. This allows for flexibility as design changes happen in either work area.

To run Annotation, access it from the Tools menu in either the schematic or PCB editor:

When prompted, select the direction to push changes (from schematic to PCB or vice versa). The designators will update accordingly.

Regularly annotating changes ensures your designators are always in sync. This improves cross probing accuracy.

Cross Probe Between Tools

With synchronized designators, Altium allows for easy cross probing between the schematic and PCB layout views. This invaluable for checking connectivity and that your design intent transfers correctly to the board layout.

To cross probe, click on a reference designator in either tool. Altium will highlight the component and jump directly to its counterpart view.

For example, clicking a designator on the schematic will center the cursor on the associated PCB footprint, and vice versa:

The bi-directional cross probing acts as a sanity check as you move from schematic to board layout. You can verify components have correctly mapped footprints and connectivity has maintained integrity.

This ability to cross probe on designators saves significant time over manual checks. It also reduces chances for error during the development process.

Highlight Net Connectivity

In addition to cross probing on a single designator, Altium can intelligently highlight all connected nets in a design. This makes it easy to examine how components are wired together.

To view net highlights:

1. Click on a reference designator for a component on either the schematic or PCB.
2. In the Properties panel, go to the Net/Bus tab.
3. Click the Highlight button for the desired net.

This will highlight the entire net with dots along the wire paths. All components connected to that net will also highlight:

Use net highlighting when reviewing schematics for errors. The visual connectivity map makes it easy to follow nets and ensure components are properly wired.

On the PCB, highlighting nets provides the same utility for examining routing and connectivity between components. This can reveal any discrepancies between layout and schematic intent.

Identify Connectivity Issues

In addition to manual checks with highlighting, Altium includes automated tools for identifying connectivity issues. This can catch errors in reference designators and component connections early in the process.

On schematics, the most powerful tool is the Electrical Rules Check (ERC) discussed previously. In addition to reporting duplicate designators, ERC does a full connectivity check. It will report:

• Unconnected pins
• Nets driving multiple pins
• Conflicting net names
• Other errors preventing clean connectivity

ERC can help identify issues with designators, such as components mapped to the wrong footprints. Running ERC periodically on the schematic provides rigorous checking to avoid propagation of errors to the PCB layout.

On the PCB side, the Design Rule Check (DRC) plays a similar role. DRC scans the routed board for errors including:

• Overlapping components
• Incorrect clearances
• Unsuitable component placements
• Missing connections

Altium flags all errors in the Messages panel similar to the ERC. DRC validation on the routed board layout catches any discrepancies in transferred design intent. This includes problems with designators mismatching between tools.

Leveraging both ERC and DRC ensures your design maintains clean connectivity and synchronization. Automated checking supplemented with manual cross probing provides complete design assurance. Altium's robust tools for tracking reference designators facilitates moving from schematic to layout while minimizing errors.

Tips and Best Practices

Here are some useful tips and best practices to employ when working with reference designators in Altium:

• Establish a consistent designator naming scheme early - Prefixes based on component type is an ideal approach.
• Run ERC on schematics frequently - This catches errors like duplicate designators early.
• Use net identifiers rather than names - This avoids name mismatches between tools.
• Cross probe between tools often - Verify correct footprint mapping as you move to layout.
• Annotate after major design changes - Keeps designators properly synced between tools.
• Analyze highlighted nets for connectivity - Use highlighting to follow and validate net routing.
• Run DRC on routed PCBs - Catches errors in transferred schematic connectivity.
• Allow Altium tools to handle designator updates - Automated propagation avoids manual edits.

By following these guidelines, you can avoid common issues related to reference designators in complex PCB designs. Altium provides the capabilities needed for smooth tracking of designators between schematic and layout. Proper use of these features is key to an efficient and successful PCB development process.

Frequently Asked Questions

What are some common causes of designator issues in Altium?

Some common causes of designator problems in Altium include:

• Manually changing a designator on one sheet but not updating the other tools
• Duplicating components on a schematic without updating the designators
• Not running Annotation to synchronize changes between tools
• Copied-and-pasted components keeping the same designators
• Errors in ERC/DRC checks identifying connectivity issues

How can I avoid duplicate designators in my designs?

Setting unique default designator prefixes for each component type will help avoid duplicates. Also run ERC checks on the schematic periodically to catch any slipping through. Finally, allow Altium to automatically handle designator assignments rather than manual editing.

Why is cross probing important when working across tools?

Frequent cross probing validates that component footprints have correctly mapped from schematic symbols to PCB layout. It also verifies connectivity has maintained integrity during the design transfer. Cross probing essentially safeguards against errors as you move from schematic to routed board.

How do I cross probe to a component on the PCB in Altium?

To cross probe from the schematic editor to the PCB layout, simply click on the reference designator for the desired component. Altium will automatically center the PCB view on the associated footprint. The same process works in reverse from the PCB to schematic.

What is the easiest way to highlight and analyze nets in Altium?

Clicking a component's designator and using the Highlight Net option in the Properties panel is the fastest way to visualize nets. This will trace the net across the schematic or PCB layout. You can then examine the routing to validate proper connectivity.