The contents of the Differential Pairs tab in the Rule Editor dialog are described below. This tab allows you to calculate the track width, track spacing, differential impedance, and delay per unit length. The values specified for each conductor layer in the differential pair rule stack are used to calculate these values.
Note
- To correctly calculate track widths and spacings, impedances and delays, accurate values for layer thickness, resistivity, dielectric constant and loss tangent must be provided in the layer configuration.
- When defining Differential Pair rule stacks in the eCADSTAR rule editor, Differential Pair tab, the track widths defined should comply with the min and max track width values defined in the Tracks tab. If the Differential Pair Track width is outside of the range of the min and max track width values then DRC will return errors that the widths of the diff pair are in error.
Default differential pair rule stack
| Item | Description |
|---|---|
| Default differential pair rule stack | Allows you to specify an existing differential pair rule stack from the Differential pair rule stack list. This is used, by default, by any differential pairs in the current design. If a default track width stack is defined, then signals which do not have a differential pair rule stack specified in Constraint Browser will use the default widths and gaps. |
Differential pair rule stack
| Item | Description |
|---|---|
| Differential pair rule stack box | Allows you to create a rule stack for differential pairs by typing its name and clicking Add. Multiple rule stacks can be created simultaneously by entering multiple names, separated by a space. The values that you enter can be selected in the Default differential pair rule stack box. If you create a rule stack for differential pairs, then you must add values for Track width and Track spacing in the Differential pair rule stack table, for at least one layer. |
| Add | Moves the values that you enter in the Differential pair rule stack box to the Differential pair rule stack list, below. |
| Differential pair rule stack list | Displays the differential pair rule stacks that you enter by clicking Add. |
| Calculate differential impedance -> Track Width | Displays the Calculate
Differential Impedance -> Track Width dialog. This dialog
allows you to calculate the following:
You can add the calculated values to the Differential pair rule stack table by clicking Apply calculated results to diff. pair rule stack in the Calculate Differential Impedance -> Track Width dialog. |
| Calculate differential impedance | Calculates the differential impedance and delay, based on values for Track width and Track Spacing that you specify. The calculated values are displayed in the Differential pair rule stack table. |
Differential pair rule stack table
| Item | Description |
|---|---|
| Conductor layer | Lists the conductor layers that are added in the Board tab. |
| Track width | Displays the calculated value for track width in each conductor layer, or allows you to define a value for each layer and press Return. If you create a rule stack for differential pairs, then you must add a value for Track width for at least one layer. |
| Track spacing | Displays the calculated value for track spacing in each conductor layer, or allows you to define a value for each layer and press Return. If you create a rule stack for differential pairs, then you must add a value for Track spacing for at least one layer. |
| Differential impedance [Ω] | Displays the differential impedance that is calculated using the values that you specify. |
| Delay | Displays the delay per unit length, in nanoseconds, that is calculated using the values that you specify. This column is displayed only if delay is set to nanoseconds in the in . |
Note
You must restart Rule Editor to apply changes to the units for delay that you specify in the Application Settings dialog, Interaction tab.
You must restart Rule Editor to apply changes to the units for delay that you specify in the Application Settings dialog, Interaction tab.
