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Switching Power Supply - EM Reduction

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c_oflynn

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vantis high speed board design techniques

Hello,

First off - this is my first post to this forum so hopefully it is in the right spot! Looks like a great forum, got referred here from Avrfreaks.net.

I am working on a PCB design that includes a little switching power supply based on the LM2651. What are some good ideas to reduce the fields generated by it and to minimize interference? So far what I've got are:

-external diode on inductor to supplement internal one (from Datasheet)
-4 layer PCB with Ground plane on one layer
-Top, Middle, and Inner layer all have a ground pour around the area, is that a good idea? So pretty much every layer at that point is as much ground as I could get with lots of vias connecting them all.
-Minimal trace length, etc.

Regards,

-Colin
 

high speed board design techniques amd

Minimize the loop area formed by the traces that carry high currents.
 

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    c_oflynn

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Perfect:
"Minimize the loop area formed by the traces that carry high currents."

but, if you wanna more information, search for this books/articles:

"EMC Design Guide for Printed Circuit Boards" Ford Motor Company
or
"High-Speed Board Design Techniques" Application Note from Vantis, AMD
or (for advanced questions)
"High-Speed Digital System Design—A Handbook of Interconnect Theory and Design Practices" Stephen H. Hall, Garrett W. Hall, James A. McCall, 2000 by John Wiley & Sons, Inc.
 

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    c_oflynn

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c_oflynn said:
First off - this is my first post to this forum so hopefully it is in the right spot! Looks like a great forum, got referred here from Avrfreaks.net.
Click to expand...
Frankly speaking, this is the best forum on electrical/electronic related topics that I've ever joined.

For example, you can find many good references. Of course, you can find some good e-books/e-references on your topic too. There are free and you can download by following the links below:

High Speed Digital Design:Handbook Of Black Magic


High-Speed Signal Propagation: Advanced Black Magic


High-Speed Digital System Design: A Handbook of Interconnect Theory and Design


High-speed Circuit Board Signal Integrity


Signal Integrity Issues and Printed Circuit Board Design


Signal Integrity - Simplified- Prentice Hall PTR


Digital Signal Integrity - Modeling and Simulation with Interconnects and Package


Signal Integrity Board Design and Simulation


Controlled Impedance PCB Layout Design


Testing for EMC Compliance Approaches and Techniques


Design Techniques and Testing for EMC (19 articles)
 

    C

    c_oflynn

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Hi,


Wow thanks everyone, looks like I've got some reading to do now ;-)

Warm Regards,

-Colin
 

Reduce track area and length which are switching,( drain to power inductor and diode) the ground can have a big plane.
I think 4 layer board is overkilling, it will only increase the cost.
8)
 

Reduce track area and length which are switching,( drain to power inductor and diode) the ground can have a big plane.
I think 4 layer board is overkilling, it will only increase the cost.
Click to expand...

Ah - the switcher is just part of a bigger board that needs to be 4 layers pretty much. So if I've already got the layers, would it be wise to flood them with ground in that area as well as doing the aftermentioned things was what I was wondering.

Regards,

-Colin
 

8) "Larger the ground Plane better" does not always hold good in switching power supply design.

keep the shortest routes for feedback and switching tracks
 

    C

    c_oflynn

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I recall there is a good article by Marty Brown in the internet. Also try the EMC compliance website. They have a lot of good articles.
 

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