Power Integrity

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How will the technology inside the data center change to support the latest high-traffic needs?

We searched for a superior cable for PDN measurements, then decided to create our own. Here’s the story.

The goal of power integrity (PI) analysis is to ensure not only sufficient but also stable power to all chips in a system. This article uses the example of a DDR4 application to explain the choices surrounding the use of decoupling capacitors to reduce impedance, and which performance parameters are critical to success.

Recently, Signal Integrity Journal caught up with Todd Cutler, Keysight’s VP and General Manager for Design & Test Software about product development, innovation, and the latest developments in SI/PI design.

There seems to be more standards every day, and some have rumored that there is a movement to merge or consolidate some existing standards. We will examine some of the standards and how they came to be. For starters, we will limit ourselves to three main types of standards in the industry: on-board or internal, input/output (I/O), and networking. I/O and networking are similar, but networking standards typically apply to longer distance links than I/O standards. There is, as often happens, overlap between these types, and some, such as PCI-express, have standards that apply to more than one of them.

Understanding how to make and interpret power supply impedance is very useful for optimized, low noise power supply design. With a simple pair of homemade probes, it’s easy to make the measurements using a compact VNA. Read on to find out how.

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.” 

Obtaining accurate measurement data requires either accurate knowledge and accounting for the probe and fixture influence OR calibration methodology to remove these effects prior to measurement.

A TDR (time domain reflectometer) is an instrument that probably has the fastest rise time of any instrument in your lab, but how accurate is it? Eric tests accuracy using a DC Ohmmeter in this piece.