Stats

More Content

Impedance calculator issue

Jessicak

I am using the impedance calculator for a 14 layer PCB, and although I have only roughly set up the stack the data is not too far out. However I am getting a stupid width for a 50R impedance of 22mm. the 14 layers give a total thickness of 3mm with Fr4 @0.2032mm and copper of 0.03048, dielectric constant of 4.5. What am I missing?

I tried an old design just 4 layers and the values were equally ridiculously out.

Thanks Jessica.

  • excellon1
    +1

    Jessica in order for the PCB editor to calculate impedance the physical reference layer needs to be set as a Plane.

    For example Layer 1 is top and set as a conductor. L2_GND should be set as a plane layer. Doing so will allow you to calculate the desired impedance on layer 1.

    It can be confusing because one might think it would not be possible to route traces on a plane layer but this is not the case. On your stackup in the picture just set L2_GND & L5_PWR to a type of "Plane" and the
    impedance solver should work as desired.

  • Jessicak
    0 in reply to excellon1

    Thank you so much for your help Excellon1, I knew I must have missed something

Cadence Guidelines

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.