Need an example of how to design a controlled impedance differential pair of pcb routes

Bankole Paris wrote on Mon, 13 January 2014 14:36

I need an example of how to design a controlled impedance differential

pair of pcb routes

using Cadsoft Eagle vsn 5.12.0.

 

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In V5 and before, you have to do the routing manually.  First, you need to

figure out what the trace width and separation should be (EAGLE will not

help you be an engineer).  Then once you have that, what I do is figure out

what grid setting I need to get the separation exactly right when routing

that trace width.  I do this by drawing a quick diagram and figuring out

center-to-center spacing of the traces.  Then I usually set my grid to 1/2

of that and then route to make sure 2 grid spaces are between the diff pair

traces.  Diagonals are different and if you really want exact then you need

to do some calculations and move them closer to each other.

The summary is EAGLE won't help you other than letting you put traces

exactly where you need them.  So you have to do some low-level design work

to get these to work.  I've done dozens of boards this way and they

function just fine.

Cheers,

James.

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James Morrison  ~~~  Stratford Digital

Specializing in CadSoft EAGLE

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James,

Thanks for taking the time to explain. Since i posted my question

I saw an Altium example showing that both traces are simultaneously both traces that Eagle vsn 6 

James,

Thanks for taking the time to answer. Since I posted the question

I saw a Altium example that shows both traces being routed simultaneously

after a minor amount of setup. I later found out that eagle offers the same thing in vsn 6. 

James,

Sorry for the multiple sends, I keep hitting the wrong keys as I am typing.

Thanks for taking the time to answer. Since I posted the question

I saw a Altium example that shows both traces being routed simultaneously

after a minor amount of setup. I later found out that Eagle offers the same 

thing in vsn 6.  I am considering buying DipTrace for $895.00 since upgrade

to Eagle vsn 6 will cost me $549.00. I have been with Eagle for years but I 

need to save $$$. 

Regards,

Bankole