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SergeyM , 12-09-2024, 08:19 AM

Lesson 3, slide #41, the Ztarget is 3.1 mΩ. In slide #45, the Ztarget varies, but it is not nearly 3.1 mΩ. Can you please explain why I see two different Ztarget values and what I might be missing?
My second question is: which value of current should I use to calculate Ztarget? Is it I = Pmax / V (which leads to 3.1 mΩ in the example), or is it |Ipositive|, as shown in the example of slide #45?

Miuš , 12-12-2024, 01:18 PM

Hello Sergey,

I contacted Keith directly and this is his response:

"My courses are design guidelines, intended to be applied to different situations, now and in the future.

Q1: Any actual quantities used in my slides, such as “3.1 milliohms”, are just worked examples to help demonstrate the EMC design techniques I recommend.

Such quantities are never intended to be used in specific designs (unless my text specifically says so!).

This is because different circuits and components will generally need different values of these quantities to achieve their intended functionality – not EMC.

Please let me know if you think I should add a note on every slide, that says something like:
“Any quantities stated in these coursenotes are only illustrative examples.
For each specific design, we must always discover or design the values of the quantities that are needed for that specific design.”

Q2: IC’s Ztargets for decoupling their power rails are specified by ICs’ manufacturers.

Alternatively, the manufacturers should specify how to calculate them.

The attached document “ Computational Intelligence Based Selection and Placement of Decoupling Capacitors: A Comparative Study ” says:

Miuš , 12-12-2024, 01:19 PM

Where the IC manufacturer is not helpful, the attached document by Barry Olney: “The Target Impedance Approach to PDN Design” gives a guideline for calculating a Ztarget:

Miuš , 12-12-2024, 01:19 PM

Target impedance (Z) is only concerned with the ICs achieving their intended functionality – not EMC, so I don’t cover this in my EMC courses.

However, I will add the attached two documents on PI and Ztarget, to my future course material!"

Miuš , 12-12-2024, 01:20 PM

QDrives , 12-12-2024, 07:39 PM

For PDN you should watch videos from Steven Sandler and Heidi Barnes.
https://www.youtube.com/watch?v=YPm8fTgV_2w
https://www.youtube.com/watch?v=NOGw-M-DPN8
https://www.youtube.com/watch?v=oL6qjhJH_m4
https://www.youtube.com/watch?v=ejAApIv1cR8
And many more...