HyperLynx: There’s an App for That

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When we’re laying down power planes, we’re asking, “Do we have enough metal to carry the current needed, and will neckdowns cause problems due to excessive voltage drop?” The DC drop app will allow you to analyze and visualize current flow under steady state conditions, so you can quickly identify and correct potential problems.

When we’re designing an AC power delivery network (PDN), we’re placing decoupling capacitors, and we’re asking, “Do we have enough capacitors, with the right values, close enough to the devices they need to service?” The traditional approach to placing decoupling capacitors has often been called “sprinkle and pray,” which results in overdesign and higher manufacturing costs. Being able to determine how many capacitors are actually needed makes the process more reliable and frees valuable board space that would have been occupied by unnecessary capacitors.

Pulse response analysis considers a group of signals that should have nearly identical electrical characteristics to see if there are any outliers. This is first-order signal integrity; I don’t need the exact driver model; I just need a technology model with about the right impedance at about the right edge rate. That makes the setup and simulation process much simpler. I can quickly analyze a group of related signals (think DDR data or address bus) to see if anything stands out, then go from there.

Johnson: This is the “signal and power integrity for the average engineer” you’ve been talking about in past interviews?

Westerhoff: Right. It’s based on reframing the way we typically think about signal and power integrity. Typically, we’re told that signal integrity and power integrity need to be detailed, quantitative, and exact, down to the millivolt or picosecond. That results in a process that can only be performed by SI/PI experts. The analysis we perform with design apps is more of a qualitative approach. We’re running first-order analysis during layout to tune things as we lay them down, identifying and resolving obvious problems as we go. Remember, design apps aren’t trying to perform signoff analysis; we assume the normal signoff process still applies.

Regression apps are more what we typically consider as signal integrity because they’re specific and quantitative. They’re also different in that they are standards-based and focus on spec compliance instead of device-specific performance. It’s much easier to determine whether a channel is compliant with a spec because all you need is the layout database and which protocol you want to analyze it for; everything else is already known. Traditional serial channel analysis involves vendor IBIS-AMI models, which is a much more complicated and case-dependent proposition. Protocol compliance analysis is well-defined once you know the protocol, so it can be automated.

The extraction and electromagnetic modeling process for serial channel compliance is pretty complex, so this isn’t a “while you wait” process; it’s an automated, overnight run. Load the layout database at the end of the day, start the compliance app, and have a report ready for the next morning. That’s the workflow.

Setting up a regression app is more involved, so it can make sense to have an SI/PI expert set up the initial run and save that setup to a library. That makes sure that everything is configured correctly to ensure a correct final result. Once the setup is in the library, the designer can rerun the analysis as often as they need at the push of a button.

Johnson: How accurate are the results we’re talking about here? How well do HyperLynx Apps results compare to HyperLynx?

Westerhoff: Excellent question. As we said, signal and power integrity are traditionally all about accuracy. The important point here is that HyperLynx Apps are HyperLynx. We’ve just created a simpler front-end for specific tasks. We’re building on the infrastructure HyperLynx already has, so the accuracy and analytical capabilities are the same. In some cases, the app calls the automated flows that have existed in HyperLynx for some time now.

Johnson: What happens if a designer runs across a problem that they can’t resolve using the app?

Westerhoff: Good point. We’re giving PCB and hardware designers the ability to run analysis themselves, but the design problems can still be quite complex. They eventually will run into something that they can’t resolve, so then what? Remember that HyperLynx Apps use the same database and analytical methods as traditional HyperLynx. That means that when a designer runs analysis and gets stuck, the HyperLynx simulation setup and results already exist. An experienced user can open up the project with traditional HyperLynx and dig right in.

Johnson: The designer escalates the problem, so the SI/PI experts can take a look at it?

Westerhoff: Right, but the SI/PI experts get the problem handed to them on a silver platter, with a complete simulation setup and results available. It’s all ready to go.

Johnson: When will these HyperLynx Apps be available?

Westerhoff: We began shipping HyperLynx Apps with the 2.11 release this March. We’ve been working with select customers on this concept for a while, and we’ve just opened it up for general use.

Johnson: Thanks for speaking with me, Todd.

Westerhoff: Thank you, Nolan.

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