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80 DESIGN007 MAGAZINE I OCTOBER 2019 draw box with default serpentines to which you can pull up/down or to the left/right to add or remove length (Figure 11). Instant feed- back is given on the cursor with the min and max length rule values shown for that item and where you are in relation to these values. If design time is of further concern, tuning can be performed automatically. By selecting a group of single-ended or differential pairs, au- tomatic tuning can be activated. Automatic tun- ing can complete this process up to 45X faster. What if you make a late-stage change and want larger spacing between the nets? The tool you use should enable you to simply change the design rule to the larger value instead of forcing you to tediously reroute all the trac- es again. Then, the DRC visualizer can display any violations on the board due to the change. It will cross-hatch the traces to indicate the ex- act areas of violations. You can then select the affected nets and select the repair function. Within seconds, the autorouting algorithm re- spaces the nets. This saves considerable time when dealing with inevitable design changes. 4. Plane Creation and Dynamic Fill Once the design has been completely routed, the focus turns to adding power and ground connections by using plane shapes. An intelli- gent layout tool should not require you to draw plane shapes that cover an entire layer based on the board outline. Even if additional nets are included, being able to draw shapes within the main plane area should not cause priority problems. If a complex shape must be added, being able to draw basic shapes like rectangles quickly and combine to one shape will dra- matically reduce the shape creation time. When dealing with high-current, RF, or sen- sitive, high-speed reference planes, being able to instantly see plane adjustments due to via and trace locations reduces cycle time pro- ducing your final plane fills. Having the capa- bility for planes to adjust dynamically when moving or adding a via, adjusting the plane outline, or adding a new sub-plane gives the designer instant feedback to make the proper decisions. Conclusion The routing tool you choose should offer a wealth of routing automation capabilities that enable you to create PCB boards faster with better results, including: Figure 11: Interactive tuning.

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