Calculate Differential Impedance -> Track Width

This dialog is displayed by clicking Calculate differential impedance -> Track Width in the Differential Pairs tab in the Rule Editor dialog.  It allows you to calculate the following:

• The track width, differential impedance and delay per unit length, based on target values for differential impedance and track spacing that you specify.
• The track spacing, differential impedance and delay per unit length, based on target values for target differential impedance and track width that you specify.

Different fields are displayed in this dialog depending on whether you select Track width or Track spacing in the Calculation Mode field.

Item	Description
Calculation Mode	Allows you to select either Track width or Track spacing. Track width: if selected, the Calculate Track Width button and the Rounding precision for track width box are made available, and the Track spacing column can be edited. Track spacing: if selected, the Calculate Track Spacing button and the Rounding precision for track spacing box are made available, and the Track width column can be edited.
Differential pair rule stack	Displays the Differential Pair Rule Stack names that you entered in the Differential Pairs tab.
Rounding precision for track width	For a Track width value, this field allows you to set the value by which the track width is incremented in order to reach the Target Differential impedance value that you specify. When you click Calculate Track Width, the Track width value is automatically incremented by this value until Differential impedance calculated value is as close as possible to the Target Differential impedance value. The most accurate results are produced by specifying smaller values. Note If you change the units in the design, then the precision of the calculated track width value may appear to be different as the value is displayed using the new units. However, the specified precision is maintained. For example, in units of mm, specifying a rounding precision of 0.01, might produce a track width of 0.43000. If this value is saved and the units are changed to inch, then this saved value is changed to 0.01693 in the Differential Pairs tab. If the units are set to mil in eCADSTAR, then the calculated track spacing may be displayed with higher precision than the value specified in the Rounding precision for track width box.
Rounding precision for track spacing	For a Track spacing value, this field allows you to set the value by which the track spacing is incremented in order to reach the Target Differential impedance value that you specify. When you click Calculate Track Spacing, the Track spacing value is automatically incremented by this value until Differential impedance calculated value is as close as possible to the Target Differential impedance value. The most accurate results are produced by specifying smaller values. Note If you change the units in the design, then the precision of the calculated track width value may appear to be different as the value is displayed using the new units. However, the specified precision is maintained. For example, in units of mm, specifying a rounding precision of 0.01, might produce a track spacing of 0.22000. If this value is saved and the units are changed to inch, then this saved value is changed to 0.00866 in the Differential Pairs tab.or example, in units of mm, specifying a rounding precision of 0.01, might produce a track width of 0.43000. If this value is saved and the units are changed to inch, then this saved value is changed to 0.01693 in the Differential Pairs tab. If the units are set to mil in eCADSTAR, then the calculated track spacing may be displayed with higher precision than the value specified in the Rounding precision for track spacing box.
Calculate Track Width	Calculates values for Track width, Differential impedance calculated value [Ω], and Delay or . These values are calculated using the target differential impedance and track spacing values that you enter in the Target differential impedance [Ω] and Track Spacing columns, respectively.
Calculate Track Spacing	Calculates values for Track spacing, Differential impedance calculated value [Ω], and Delay or . These values are calculated using the target differential impedance and track width values that you enter in the Target Differential impedance [Ω] and Track width columns, respectively.
Apply calculated results to diff. pair rule stack	The values that you enter in the attribute table in this dialog, as well as the values that are calculated by clicking Calculate Track Width or Calculate Track Spacing are added to the Differential pair rule stack table, in the Differential Pairs tab.

Differential Impedance table

Allows you to enter a target differential impedance for each conductor layer, and either a track width or track spacing value, depending on the selection you make in Calculation mode. The calculated values for track width or track spacing, differential impedance, and delay are displayed for each layer in the table.

Item	Description
Conductor Layer	Lists the conductor layers that are added in the Board tab.
Layer attribute	Displays the attribute value for each Layer.
Target Differential impedance [Ω]	Allows you to specify a target value for differential impedance. When you click Calculate Track Width or Calculate Track Spacing, this value is used as a target when calculating the differential impedance, delay, and track width or track spacing values. Calculated values will be as close as possible to this value.
Track spacing	If Track width is selected in Calculation Mode: enter a value for track spacing and press return. If Track spacing is selected in Calculation Mode: the track spacing is displayed that is calculated for each layer, using the values specified in the Target Differential impedance [Ω] box and Track width boxes. This value is displayed when you click Calculate Track Spacing.
Track width	If Track width is selected in the Calculation Mode field: the track width is displayed that is calculated for each layer, using the values specified in the Target Differential impedance [Ω] and Track spacing boxes. This value is displayed when you click Calculate Track Width. If Track spacing is selected in the Calculation Mode field: enter a value for track width and press return.
Differential impedance calculated value [Ω]	The value for differential impedance that is calculated for the relevant layer, using the values specified in the Target Differential impedance [Ω] box, and either the Track spacing or Track width boxes.
Delay	The delay per unit length, in nanoseconds, that is calculated for the relevant layer, using the values specified in the Target Differential impedance [Ω] box, and either the Track spacing or Track width boxes. This column is displayed only if delay is set to nanoseconds in the in .