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
  • A365 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 to Use a Star Point for Analog Ground and Digital Ground Connection

    July 7, 2017

    宇宙旅行の背景

     

    I’ve found that the hardest part of dating for me is meeting people in the first place. As an engineer, I spend a large portion of my life in front of a computer, not out mingling. That’s one reason I think dating websites and apps are a great idea. They help me make connections I might never be able to otherwise. Forming a bond with another person is difficult, but linking analog and digital ground planes are even harder. Noisy digital chips can cause interference in your nice analog circuits. Thus they have to be separated, but they still need to be referenced to the same ground. If you connect the planes willy nilly you can create more problems than you solve. That’s where the star ground comes in. A star ground will let you join together different grounds for certain mixed signal circuits.

     

    The Mixed Signal Grounding Problem

    Like dating, grounding mixed signal PCBs is a complex issue with many problems and solutions. You know that you need to keep your analog and digital signals separate to reduce EMI, but they also need to be grounded together. Improper grounding can result in large ground loops that will radiate noise in, and possibly around, your circuit.

     

    The main problem on mixed signal boards is digital circuits. Digital switching chips can be quite noisy, which would not be a problem if they were alone. However, when paired with analog circuits digital EMI will often find itself mingling with sensitive analog signals. That’s why you should generally try to keep these two systems separated.

     

    Separating analog and digital circuits creates another issue, though, a floating ground. Your analog and digital chips all need to be referenced to the same ground in order to operate properly. If you connect your separate analog and digital ground planes wherever you want you can create ground loops. Large ground loops will act like antennae and radiate EMI to other parts of your board, and possibly out of your device. A star ground allows you to connect your analog and digital circuits together at a single point. This reduces the possibility of ground loops and EMI radiation.

     

    アスタリスク アイコン
    All ground connections should terminate at your star ground.

     

    Star Ground

    A lot of people have tried to describe love and failed. I’m not that bold so I’ll just outline star grounds. A star ground is a single point that connects analog and digital grounding planes so as to eliminate ground loops. It doesn’t necessarily have to be in the shape of a star, but the idea is that each connection is made at a single central point.

     

    If you want to have two girlfriends at the same time (which I don’t recommend) you should keep them separated. In the same way, your analog and digital circuits should interact as little as possible. You should use separate power rails for each, and connect them only at the star point. This will ensure that ground loop areas are minimized and that analog and digital signals don’t mix and interfere with each other in the ground planes.

     

    When to Use Star Grounds

    In my experience it’s not enough to just know what to do, you need to know when to do it. I know couples hold hands, but I’ve found that I shouldn’t try to hold hands right after sneezing. There are some situations where using a star ground is appropriate, and some where it’s not.

     

    The perfect time to use a star ground is when you have a single PCB with a single ADC/DAC on it. In that kind of system, you can make your star point the grounding point for your converter. Then, connect your analog and digital ground planes on either side of the converter at that same point as well. This will help you greatly reduce noise in your mixed signal circuit and make grounding a breeze.

     

    Like I said earlier, once you get into more than one relationship, things get complicated. If you’re designing a multi-card system, or are using more than one converter, a star ground might not work for you. The problem is that you’ll have more than one star point, creating the potential for lots of ground loops. The whole idea of a star ground is that everything is connected at one point. If you can’t connect everything at one point, don’t even try.

     

    電子回路
    Keep your circuit well grounded.

     

    People aren’t meant to stay separated, but analog and digital signals certainly are. If you don’t properly ground your mixed signal circuit, things will get noisy. A star ground can help reduce EMI on your PCB and keep everything in its right place. However, you should take care to only use a star ground in systems with a single converter. Once you get into more complex systems creating a single star point becomes almost impossible.

     

    Online dating can make your love life much simpler. CircuitStudio can make your work life easier. It has a great selection of advanced features that will help you design a board with minimal EMI.


    Have more questions about star grounds? Call an expert at Altium.

    most recent articles

    Back to Home