Issue link: https://resources.pcb.cadence.com/i/1532922
Advanced Spacing Constraints Notice we have standard spacing constraints applied like you would for any standard design, high-speed or not. Those rules will be applied immediately to any nets using the Constraint Set. Of keen interest is how to set up spacing for differential pairs. Let's say we want the differential pair traces to be 60 mils (1.524 mm) away from all other objects (except between their own single-ended traces within the diff pairs of course). In this case, we create a Spacing Constraint Set named SCS_DIFF (shown below) and set its Line To value to 60 mils (1.524 mm). You can double-click the Line To column to see what all objects we are requiring the differential pairs to be at least 60 mils away from, in case you need to do some fine-tuning there. But what about differential pair to differential pair spacing? In our design, we don't need diff pairs (like TX and RX) to be more than 20 mils apart. So we need to tell the Constraint Manager that the SCS_DIFF class members only need to be 20 mils apart from other SCS_DIFF class members. That will require a Net Class-to-Class spacing. Before Creating a Class-to-Class spacing, we must ensure that we have Net Classes applied where appropriate. Navigate to the Net > All Layers worksheet, then highlight all the nets you want inside a differential pair net class that we will call CLS1_ DIFF (shown below). If you forget any nets, you can CTRL select those as well, then right click and choose Add To – Class to add them to the CLS1_DIFF net class. 58 www.cadence.com OrCAD X Constraint Management Guide