Calculation of differential pair impedance

[robertferanec]

Thank you for watching the videos. No, I don't know how Cadence calculates the impedance.

[Mohammad]

Thank you ❤️ I have learned from you a lot. Do you know what IPC standard Allegro uses for impedance calculations?

[robertferanec]

Only trust numbers from your PCB manufacturer. Everything else is just approximate.

PS: I have explained this many times. Only PCB manufacturer can give you exact numbers, because manufacturing controlled impedance tracks is not only about putting theoretical numbers into a calculator - these numbers will change during PCB manufacturing process e.g. final dielectric thickness may be different.

[Mohammad]

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?