Power electronics
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.
- Intermediate
- 10 lessons
About this course
Most decoupling advice is passed on as a rule without its reasoning, which is why it stops working the moment a board is unusual. This course rebuilds the reasoning from the transient current a device demands, through the loop inductance that decides whether the charge arrives in time, to a review you can run on a finished layout.
Every number given here is tied to a stated context. Where your device's datasheet disagrees with a general rule in this course, the datasheet measured and the rule did not.
Course contents
In order. Each lesson assumes the one before it.
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What a Decoupling Capacitor Actually Does
Why a schematic cannot tell you whether the decoupling will work.
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The Transient Current Demand of a Digital Device
How to estimate how much current your device demands, and how fast.
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Loop Inductance: The Number That Decides Everything
Where the nanohenries come from, and which of them you control.
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Placement: Why Distance Matters and How Much
Why “within X mm” hides the variables that actually decide.
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Via and Pad Patterns That Keep Inductance Low
Vias, pads, and the thermal relief that quietly costs you half a nanohenry.
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Choosing Values: The 100 nF Habit Examined
What sets the value, and when the 100 nF default stops reaching.
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Bulk, Mid and High Frequency: Dividing the Work
How to split the frequency range by working from the load.
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Anti-Resonance: When Two Capacitors Are Worse Than One
Why mixing values can raise the impedance instead of lowering it.
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Plane Capacitance and the Power Distribution Network
Target impedance, and how much of it your board actually needs.
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A Decoupling Review Checklist for a Finished Layout
Twenty minutes over the finished layout, cheapest fixes first.