Don’t Get Caught Sleeping: Resolve PCB Power Distribution Problems

January 2, 2018 Altium Designer

Couple in house dressed warmly because it’s cold inside

 

 

I’ve got a heating problem at the moment—after 30 years of service to the various owners of this house, my furnace is finally throwing in the towel and no longer providing heat. Unfortunately, this has come at a, let’s say, inopportune time with it hovering just under freezing lately, and with nights being even more frigid. We installed an ad hoc heating system comprised of the gas fireplace and several space heaters; however, this is not a long-term nor an ideal solution. Goldilocks would have no luck finding a place to nap here as each room is either too hot or too cold. Ghost stories, blankets, and porridge help in the meantime but what we need is our regular heat distribution network to be running correctly again before we turn into bears ourselves.

 

You probably won’t have three bears walk in on your PCB design, but your power delivery network (PDN) design for printed circuit boards (PCBs) can still be make-or-break for your good night’s sleep (or afternoon nap). Without the power being distributed correctly to the devices that need it, a circuit board could run into the same kinds of problem that I am having with the uneven heat distribution in my house. The circuit board might be too lumpy with its power and overheat, or too sparse to distribute energy and heat effectively.

 

Unfortunately, PCBs don’t usually come with picture books to show you where you’ve gone wrong in your design; but, there are tools that you can use to see exactly how their distribution of power on the layout looks. PDN analyzers will report and display the power distribution on your PCB as part of the design process, giving you crucial access to a major component of any PCB design. Examining potential power distribution problems and discovering how a PDN analyzer helps you to correct these problems during layout will help you avoid costly re-designs and other potentially hazardous problems down the road.

The Problems in Designing a PCB Power Distribution Network

PDN analysis has typically been a field of nadirs and peaks: you either have a do-it-yourself analysis performed during PCB layout by a “best guess” methodology, or end up using extremely expensive equipment which requires more user knowledge. With guesstimation, you can fatten up traces to device pins known to need more power and tie those traces to the power planes with larger vias or track the amount of power plane area you need to provide a clear path from the power source to the loads. But knowing parameters and understanding general needs of designs can only direct your design to a limited level of specificity.

 

While the old guesstimation method might be tried-and-true for you, designs that need more rigorous adherence to design rules to maximize their power output or minimize their size require a greater degree of specificity to ensure accurate and effective PCB design. An over-design on the PDN makes your conductors too large and decreases space for routing while conservative power plane design can create the opposite problem with smaller power plane areas resulting in circuits running hot or too-thin traces that end up burning through like a fuse. It’s not just a matter of being unable to get comfy for your bed - not using the proper PDN analysis tool could be a matter of heavy increases in cost or PCBs which are easier to short.

 

Power components on a PCB 

Your PCB relies on a well-designed power delivery network

 

 

PDN Analyzers Can Overload the PCB Designer, Too

The other end of PDN analysis is with high-level power integrity simulation systems that can be extremely expensive and give a tremendous amount of knowledge-responsibility to the user. While they are created for extremely high-powered analysis and ultra-specific detail management, much of their information can be tedious to keep track of.

 

The main concern with PDN analysis is managing knowledge requirements and expectations: after all, tools within your PCB design software are there to decrease the amount of information you have to be able to pull from your head at a moment’s notice, and speed up your layout and design process. So while data and reports from a complicated simulation system may provide a plethora of information, having all of that information can be just as much of a burden as a boon to you as the data is more than what will be realistically applicable to you in laying out your board.


 

Picture of the PDN Analyzer menu system within the layout tool

Running a PDN Analyzer from within your PCB layout will help your design

 

The Solution to PDN Design Problems

As a PCB designer I found that what designers need is a PDN analysis system that works within their existing CAD tools that can be easily accessed. The PDN analysis system needs to be intuitive and user-friendly so that they become a natural extension of the design process. In this way you can quickly verify that the design is laid out in the best way possible for the distribution of their power and ground nets without any penalty to the designer using them.

 

The best PDN analysis systems work in real-time with the layout tools and report back their results with visual graphics providing instant analysis, modification, and re-analysis feedback. This will allow you to instantly see if the power delivery layout will work, and if not, where corrections are needed. If changes are required, then the designer can accomplish those immediately in the layout tools without needing to import and export analysis information. PDN analysis tools are intuitive to use, inexpensive and provide practical information. They can save you from costly re-designs that might be needed to correct power distribution problems on your PCB design. If you haven’t looked into these systems before, you owe it to yourself to see how they can help.

 

Whether you’re looking for a good spot to nap, or to design a good power distribution network for your PCB, you owe it to yourself to have a good network of tools to check qualities for you. Your PCB design software is the tool for your design, and with Altium Designer’s PDN Analyzer tool you can find and resolve PDN issues during layout instead of after the board has been manufactured.  

 

Would you like to find out more about how Altium can help you with your power delivery network layout on your next PCB design? Talk to an expert at Altium.

About the Author

Altium Designer

PCB Design Tools for Electronics Design and DFM. Information for EDA Leaders.

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