Free Trials

Download a free trial to find out which Altium software best suits your needs

Altium Online Store

Buy any Altium Products with few clicks or send us your quote to contact our sales


Download the latest in PCB design and EDA software

  • Altium Designer

    Complete Environment for Schematic + Layout

  • CircuitStudio

    Entry Level, Professional PCB Design Tool

  • CircuitMaker

    Community Based PCB Design Tool


    Agile PCB Design For Teams

  • Altium 365

    Connecting PCB Design to the Manufacturing Floor

  • Altium Concord Pro

    Complete Solution for Library Management

  • Octopart

    Extensive, Easy-to-Use Component Database

  • PDN Analyzer

    Natural and Effortless Power Distribution Network Analysis

  • See All Extensions

    World-Renowned Technology for Embedded Systems Development

  • Live Courses

    Learn best practices with instructional training available worldwide

  • On-Demand Courses

    Gain comprehensive knowledge without leaving your home or office

  • Altium 365 Viewer

    View & Share electronic designs in your browser

  • Altium Designer 20

    The most powerful, modern and easy-to-use PCB design tool for professional use


    Annual PCB Design Summit

    • Forum

      Where Altium users and enthusiasts can interact with each other

    • Blog

      Our blog about things that interest us and hopefully you too

    • Ideas

      Submit ideas and vote for new features you want in Altium tools

    • Bug Crunch

      Help make the software better by submitting bugs and voting on what's important

    • Wall

      A stream of events on AltiumLive you follow by participating in or subscribing to

    • Beta Program

      Information about participating in our Beta program and getting early access to Altium tools

    All Resources

    Explore the latest content from blog posts to social media and technical white papers gathered together for your convenience

    Altium Online Store

    Buy any Altium Products with few clicks or send us your quote to contact our sales


    Take a look at what download options are available to best suit your needs

    • Documentation

      The documentation area is where you can find extensive, versioned information about our software online, for free.

    • Training & Events

      View the schedule and register for training events all around the world and online

    • Design Content

      Browse our vast library of free design content including components, templates and reference designs

    • Webinars

      Attend a live webinar online or get instant access to our on demand series of webinars

    • Support

      Get your questions answered with our variety of direct support and self-service options

    • Technical Papers

      Stay up to date with the latest technology and industry trends with our complete collection of technical white papers.

    • Video Library

      Quick and to-the-point video tutorials to get you started with Altium Designer

    Power Integrity Measurements for Your Prototype Board

    Zachariah Peterson
    |  November 17, 2019

    Aristotle and Plato

    We often write about signal integrity and power integrity around here, but there is one area where we sometimes fall short: test and measurement. Both aspects of building a new device are critical for ensuring your board will work as intended and meets stringent performance requirements. With advanced systems, the level of testing and measurements required to qualify a prototype for full-scale production spans far beyond using a multimeter.

    Power integrity measurements are extremely important as more systems run at lower voltages with smaller noise margins. Power integrity problems in your board can be the source of signal integrity problems, and the two areas of qualification shouldn’t be treated in isolation. Let’s take a look at some standard power integrity measurements required for digital, high frequency analog, and mixed signal systems.

    Power Integrity Problems and Measurements

    The entire point of having a power supply on your board is to ensure your components receive a stable voltage/current. In other words, you need to make sure that the 5 V provided by your power supply is still 5 V by the time it reaches your downstream components. IR drop is an obvious culprit of DC voltage drop, but there are other problems that can arise when we consider the behavior of real components connected to a power rail.

    This is simple enough to simulate with a PDN analysis tool, but it is next to impossible to measure in a board with power and ground planes unless you install numerous test points that can connect to probes. If you are in the mood to test this, you essentially need to produce a test coupon that matches your stackup and includes test points for power/ground connections and some resistors. This is usually less important in high performance systems that run at high speed, high frequencies, or both.

    Ringing on a power rail is much more important in these high performance systems. When an IC switches, it draws a burst of current from the power supply, which induces a transient oscillation in the PDN. Designing a PDN to critically damp this oscillation is quite difficult without tools for extracting parasitics and subsequent parameter optimization, and using a series resistor to provide damping (as is done with series over-termination in transmission lines) is out of the question as it increases the PDN impedance. Therefore, the standard approach is to make the PDN impedance as small as possible within the relevant bandwidth. This minimizes the voltage fluctuation on the PDN for a given transient current draw.

    This should also illustrate the importance of decoupling, both with the right stackup design and decoupling capacitors. Decoupling capacitors have been given a rather unfortunate name as they don’t decouple anything (within the parlance of filtration). Your decoupling network needs to supply enough charge in a sufficiently short enough amount of time such that all the charge is drawn from the decoupling capacitor rather than the power supply. Transient ripple in the PDN can produce ~1 ps/mV or more of random jitter in the output from a digital IC. It is not uncommon to see clock jitter reach hundreds of ps, which creates problems in any channel running at high data rates.

    If we think about these points, we see the five primary quantities that need to be measured in your PDN:

    1. The magnitude of the voltage ripple when critical components switch
    2. The PDN impedance spectrum
    3. Jitter produced due to ringing
    4. Variance in your clock period
    5. DC stability

    Interpreting Power Integrity Measurements

    Transient Response

    Let’s look at an example so you know what to expect when investigating point #1 above. The image below shows an example oscilloscope measurement of the transient voltage response on a PDN with an oscilloscope.

    Power integrity measurements

    Example power integrity measurement results. A power rail on the surface layer is shown in blue, the internal power plane voltage is shown in green, and a test signal is shown in white. All voltage measurements are gathered with respect to the power supply return.

    Once the test clock signal turns on, we see a repetitive transient response corresponding to the rising/falling edges from the clock pulses. This is superimposed over a lower frequency transient response. This lower frequency transient response is easily seen once the test signal switches off. If downstream circuits were running at 1.8 V with 2% tolerance, this PDN would fail qualification.

    Impedance Spectrum Measurements

    The impedance spectrum of the PDN can be determined on a test coupon with an impedance analyzer or a vector network analyzer that can run in impedance mode. If you do use a vector network analyzer, make sure that you de-embed the S-parameters for your connectors (usually BNC connectors for high-quality equipment) when performing the measurement. This measurement helps explain the transient behavior on your PDN and can help you determine how the stackup, decoupling network, or both need to change to reduce power bus ringing.

    Jitter/Phase Noise Measurements

    This is most easily determined from an eye diagram using the output from a downstream component. This is a standard measurement for I/O channels and will require installing some test structures for signal integrity on your board.

    Clock Frequency Variation

    Synthesized clocks (e.g., voltage-to-frequency converters, VCOs/NCOs, etc.) that are not locked to a highly stable reference clock (e.g., with a PLL) also experience some variation in the output frequency in addition to timing jitter. This also arises from the ripple in your PDN. An example for a 500 MHz clock is shown below. Here, we see that the variance in the clock period exceeds 10% in the presence of ~250 mV peak-to-peak ringing.

    Power integrity measurements of clock period

    Clock frequency variation due to noise on the PDN. [Image source]

    DC Stability

    Measuring DC stability requires removing any blocking capacitor on the input of your oscilloscope and applying some voltage offset, bringing the DC signal into the midrange of your scope output. This allows you to see the influence of any low frequency content on the output from your power supply. You can also zero in on any hidden low frequency content by applying an FFT to your time-domain measurements.

    The key to gathering all of these measurements is using an oscilloscope with sufficiently large bandwidth, high resolution, adjustable offset, and low impedance probes with low attenuation ratio. There are plenty of options on the market, but be sure to check these specifications with your scope manufacturer.

    The pre-layout and post-layout simulation tools in Altium Designer® can give you a look into potential signal and power integrity problems in your board before your produce a prototype, giving you some hint of where potential problems may lie. You’ll also have access to a complete set of routing, manufacturing planning, and data management features in a single platform.

    Now you can download a free trial of Altium Designer and learn more about the industry’s best layout, simulation, and production planning tools. Talk to an Altium expert today to learn more.

    About Author

    About Author

    Zachariah Peterson has an extensive technical background in academia and industry. He currently provides research, design, and marketing services to electronics companies. Prior to working in the PCB industry, he taught at Portland State University. He conducted his Physics M.S. research on chemisorptive gas sensors and his Applied Physics Ph.D. research on random laser theory and stability. His background in scientific research spans topics in nanoparticle lasers, electronic and optoelectronic semiconductor devices, environmental sensing and monitoring systems, and financial analytics. His work has been published in over a dozen peer-reviewed journals and conference proceedings, and he has written hundreds of technical blogs on PCB design for a number of companies. Zachariah currently works with other companies in the electronics industry providing design, research, and marketing services. He is a member of IEEE Photonics Society, IEEE Electronics Packaging Society, and the American Physical Society, and he currently serves on the INCITS Quantum Computing Technical Advisory Committee.

    most recent articles

    Back to Home