Expert Advice on Power Integrity

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Check out this description of what is likely the fastest GaN edge-speed ever recorded.

The voltage regulator module (VRM) contributes system level noise in several ways. Power integrity (PI) engineers tend to focus on transient voltage noise related to high-speed dynamic current. Many PI simulators ignore the VRM noise and use an ideal resistor and inductor model to represent the VRM. This overly simplistic approach misses many potential system level issues.

My friend Steve Sandler pointed out a major hurdle we face in power distribution design: power engineers (who design power converters) and power integrity engineers (who design system bypassing-decoupling networks) use different vocabulary, techniques, and requirements. To understand a little better how we got here, I want to start with a prediction I heard sometime in the early 90s at one of the conference keynote speeches: “In 10 to 20 years, computers will look like hairy steamy golf balls.” 

The power electronics engineer and the power integrity engineer share a common goal: provide the system with the correct voltages, currents, and noise characteristics to achieve the desired performance. Unfortunately, they do not share much else. They generally use different tools, vocabulary, and figures of merit. As a result, both sides lose.

Microwave engineers know that sharp corners and right-angle bends have their drawback at high frequencies. So what happens if we go to the other extreme of the spectrum, to DC? Istvan Novak takes a closer look.

We have to use enough capacitors so that the PDN functions properly. At the same time, to keep cost and size in check, we want to avoid overdesign and not use capacitors unnecessarily. Read on for advice on how to find the balance.