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PCB design

PCB Grounding & Return Paths

Grounding explained as a current path rather than a set of rules: where return current actually flows, what changes with frequency, and how to review a finished board.

  • Intermediate
  • 10 lessons

About this course

Grounding is the part of PCB design most often taught as a list of rules, and the rules contradict each other. Split the analog ground. Never split the analog ground. Use a star. Never use a star. The rules conflict because each one was correct for a particular board, and the board was left out of the telling.

This course replaces the rules with the thing they were approximations of: the path the return current takes. Once you can see that path, most grounding decisions stop being a matter of opinion. You can look at a layout and say where the current will go and what it will couple into on the way.

The approach is physical rather than procedural. Current flows in loops, loops have inductance, and inductance depends on geometry. Everything else follows from those three facts.

Course contents

In order. Each lesson assumes the one before it.

  1. Ground Plane vs Ground Pour: What Is the Difference?

    Copper named GND is not the same thing as a reference plane.

  2. Return Current: The Idea That Explains Most of Layout

    Every signal you route is half a loop. The other half decides whether the board works.

  3. Why High-Frequency Return Current Does Not Follow the DC Path

    The same copper carries two different currents by two different routes.

  4. Should Analog and Digital Grounds Be Split?

    The pin is called DGND for a reason, and the reason is not the one most people assume.

  5. Star Grounding: When It Helps and When It Makes Things Worse

    A topology that solves a low-frequency problem, applied to a high-frequency one.

  6. Ground Vias and Stitching Vias: Where and Why

    A signal that changes layer needs its return to change layer too.

  7. What Happens When a Signal Crosses a Plane Split

    The trace crosses in a straight line. The return current does not.

  8. Grounding a Mixed-Signal Board, Step by Step

    One sensor, one converter, one microcontroller, and every decision justified.

  9. Connectors: What Happens When the Signal Leaves the Board

    Your careful return path ends at the connector unless you continue it.

  10. A Grounding Review Checklist for a Finished Layout

    Fourteen checks you can run in your PCB editor before the files go out.

Other courses

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    Power Integrity & Decoupling

    Why a capacitor on the schematic is not a capacitor on the board, and how to decide placement, value and count with reasoning instead of folklore.

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