Calculation of differential pair impedance

[mohammadsh8421]

Hi guys
I am using the Saturn PCB toolkit for calculating differential pair impedance and there is a 6 to 10 ohm difference between Saturn and allegro calculations for the same stack-up and trace width and spacing. can anybody help me with this problem? Which one should I trust?
Also, which IPC standard does Allegro use for calculations? IPC-2152?

 

[BigBoss]

This is normal. Saturn PCB software computes Impedance by analytic/empirical method but Allegro simulates using with EM computations. The best way is to measure it and you'll eventually find another but similar value.

 

[mohammadsh8421]

This is normal. Saturn PCB software computes Impedance by analytic/empirical method but Allegro simulates using with EM computations. The best way is to measure it and you'll eventually find another but similar value.

Thank you
Between Allegro and Saturn which one do you think is closer to manufacturer's calculations?
Do you know which IPC standard Allegro uses?

 

[BigBoss]

Thank you
Between Allegro and Saturn which one do you think is closer to manufacturer's calculations?
Do you know which IPC standard Allegro uses?

Allegro should be closer to the real value.

IPC-2581

Allegro PCB Designer enables efficient collaboration through the IPC-2581 open, neutral standard that communicates PCB build intent to manufacturing.

www.cadence.com

 

[marce]

Firstly IPC-2152 is for current, nothing to do with impedance calculations...
How are you calculating the impedance in allegro, using the 3d field solver of an app.
Have you got etch factor turned on in Saturn.