Free Trials

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

How to Buy

Contact your local sales office to get started on improving your design environment

Downloads

Download the latest in PCB design and EDA software

  • PCB DESIGN SOFTWARE
  • Altium Designer

    Complete Environment for Schematic + Layout

  • CircuitStudio

    Entry Level, Professional PCB Design Tool

  • CircuitMaker

    Community Based PCB Design Tool

  • NEXUS

    Agile PCB Design For Teams

  • CLOUD PLATFORM
  • Altium 365

    Connecting PCB Design to the Manufacturing Floor

  • COMPONENT MANAGEMENT
  • Altium Concord Pro

    Complete Solution for Library Management

  • Octopart

    Extensive, Easy-to-Use Component Database

  • PRODUCT EXTENSIONS
  • PDN Analyzer

    Natural and Effortless Power Distribution Network Analysis

  • See All Extensions
  • EMBEDDED
  • TASKING

    World-Renowned Technology for Embedded Systems Development

  • TRAININGS
  • Live Courses

    Learn best practices with instructional training available worldwide

  • On-Demand Courses

    Gain comprehensive knowledge without leaving your home or office

  • ONLINE VIEWER
  • 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

    ALTIUMLIVE

    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

    Downloads

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

    How to Buy

    Contact your local sales office to get started improving your design environment

    • 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

    How Parasitic Inductance Can Impact Your ESD Protection

    June 20, 2017

    shutterstock_552780019 (1).jpg

    When I was a kid, I was certain I was going to be a biologist. I collected all kinds of lizards, tadpoles, and insects, and spent most of my allowance on aquariums for my various creatures to live in. However, one thing really held me back. I am super grossed out by parasites. I will let a mantis or snake crawl all over me, but even looking at a tapeworm gives me dry heaves. Eventually, I went into engineering, where nothing needs weekend feedings. While parasitic parameters are bad news, they’ve never made me throw up at work. 

    In particular, parasitic inductance (L) can have a significant impact on how effective your electrostatic discharge (ESD) protection is. Managing your interfaces and using transient voltage suppressors (TVS) at your inputs are critical first steps. However, if you don’t minimize parasitic inductance all that work can go to waste. This is especially true when you’re using a TVS. If a TVS diode experiences high parasitic inductance, in the event of an ESD pulse the voltage might be allowed to overshoot dramatically and not protect your components at all. 

    Parasitic inductance in a TVS protection

    I kept lots of little creatures, like anoles, but a strenuous aversion to parasites kept me from a career in biology.

    What does parasitic inductance do to my protection ? 

    We can work this out if you look at the inductance in a TVS protection and think way back to your introductory circuits class.

    The voltage of the ESD pulse (VESD) can be considered: VESD = VBREAKDOWN(TVS) + RDYNAMIC(TVS)*IESD + LESD(dIESD/dt). If you really want to dig deep into the math, Texas Instruments has an amazing walkthrough. The key takeaway for those of us skimming this over lunch is the last term: LESD(dIESD/dt). Because t is very tiny, dIESD/dt will be huge. Even if the inductance LESD is very small, you can still have a huge voltage spike in the system.

    How do I minimize my parasitic inductance? 

    So what do you do if the problem is inherent in the traces of your PCB? The key is smart component placement to minimize shunt paths and the resulting parasitic inductance. 

    Minimize any inductance from the TVS to ground by keeping the trace short and by using direct routing. Don’t use a stub or via to connect to the ground plane, so there’s no additional path length or material to contribute to LGND. 

    The same is true of the input to the TVS: keep it short, don’t use vias or stubs. LESD can also contribute negatively to your parasitic inductance and protection capability. Keep the TVS close to the input connector, too. In addition to keeping parasitic inductance low, it will help prevent transient coupling of the ESD pulse into neighboring traces.

    Minimize trace length and don’t use vias to connect to your TVS.

     How do I position my sensitive components? 

    Keep the sensitive components that you are protecting further away from from the TVS. You don’t just want to keep the inductance  LESD small, but you’ll also want maximize the ratio of LIC to  Linput on the protection line. As Machine Design explains it, “The nonlinearity of LIC acts as a buffer to the initial peak of the ESD current pulse. This creates a substantial voltage drop toward the IC. This inductance gets smaller the closer the ESD device gets to the IC, and the voltage drop shrinks to the point where it provides no additional advantage.” 

    Basically, by putting your sensitive components further away from the input and TVS protection, you can get some of your parasitic resistance to work for you by decreasing the voltage spike of the ESD pulse that your components experience. 

    While the getting placement right is certainly not as terrifying as a worm that controls a cricket’s mind (warning: you can’t unread this), it may not be something you want to do repeatedly. If you are using similar protection methodologies in multiple products, you can design your circuits once and use modular designs to make re-use easy. PCB software, like Altium Designer®, makes modular designs simple to implement and helps you protect your PCBs. You can contact an Altium representative to help you get started.

    Check out Altium in action...

    Powerful PCB Design

    most recent articles

    Back to Home