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differential trace impedance calculation

Question asked by v.anisoveca on Jun 4, 2013
Latest reply on Jun 6, 2013 by veronika.anisoveca

Hello!

 

I am confused about the correct PCB stack-up for 100 Ohm differential trace impedance.

Can you describe me the basic rules for this and advise relevant links?

 

For example, I have differential stripline signals, which should be 100 Ohm impedance.

Dielectric thickness may vary, but at the moment I have 4mils.

Trace thickness is 0.6mils.

 

So I need to choose the correct trace width/spacing, am I right?

Previously I was used 5mils width and 6mils spacing differential traces.

But when I put all these values to some calculator it gives me only 72 Ohm of differential impedance.

What could be wrong and what should I change in my values in order to have about 100 Ohm impedance?

 

Should I trust to such kind of calculators?

 

Thank you in advance!

 

Veronika

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