Differential Pairs Report Template
Labcenter Note: This template is provided as an example. Users should either edit this document as required or create their own corporate template before using.
Since the document is largely tables the size of all the tables and graphics will change according to the project. This means that in many cases the user will have to edit the document to organise pagination.
This document contains information on all differential pairs on the PCB.
Differential Pairs - 19/12/2019 10:43:42
Property | Actual | Specified | Passing |
|---|
Notes about the data go here....
Labcenter Note: Where a route is out of tolerance or non-compliant it will be marked with a red cross in the tolerance column. You can find the route on the layout using the pin indicators in the table. Changes can be made either to the routes or to the tolerances and then the data re-loaded via the right click context menu (or from the Edit Menu).
Phase Tolerance:
This is the allowable difference in track length due to length mismatch (e.g. a corner) before we are considered out of phase. Serpentine routing is applied at the end of a corner to equalise the track lengths when we are deemed to have drifted out of phase.
It's important to note that serpentine routing for phase matching can only be applied at the end of a corner. This means that long corner (E.g. a large curve) can create a significant distance before serpentine routing can is applied.
Despite a difference in length as we corner the two tracks are not out of phase until they exceed the phase tolerance
Total Length out of Phase:
The total distance over which the two tracks are deemed to be out of phase according to the phase tolerance. Unlike the unpaired length here we are considering tracks which are obeying the pairing distance. We are measuring the length over which these tracks differ in distance from the source pad(s).
The source pads are determined by the routing direction (src->dst) and are indicated by the pin descriptions in the table. You can reverse the differential pair from the right click context menu on one of the tracks on the layout if you have routed from dst -> src . You'll then need to regenerate the table by right clicking on the table and selecting Reload Project Data .
All coupled, out of phase segments
Max Length out of Phase:
This is the maximum contiguous paired length that the two tracks are deemed to be out of phase according to the phase tolerance. It doesn't include serpentines or segments where the track separation exceeds the paired distance.
Largest length out of phase
Max Phase Mismatch:
This is an indicator of the worst case scenario and provides the largest distance that the two tracks deviate by over the course of the route.
Pairing Distance:
This is the default (and also preferred) separation of the two tracks as set in the Design Rule Manager (+ 1th tolerance).
It's very helpful to set up a design rule with the same trace -> trace clearance as this setting. See the help file for more details.
Distance between traces
Unpaired Length:
This is the total distance over which the two tracks are spaced at a distance greater than the pairing distance.
Combination of total unpaired trace segments
Max Unpaired Length:
The maximum distance that the tracks are unpaired for in the route. The actual value reported is the longer of the two lengths of track over which the separation exceeds the pairing distance.
Unpaired length generally results from serpentine segments used to equalize the track lengths. To correct an overly large reported unpaired length you need therefore to look at the corners during routing (causing the length mismatches) and/or the max unpaired separation specification (influencing the distance that the tracks are unpaired for).
It can also result from fanout from the source/receiver pins, covering the etched track distance used to get from the two pins into a paired state. Generally this is routed manually by the user and is unavoidable.
Longest section of unpaired trace
Max Unpaired Separation:
This is the maximum space between the two tracks that occurs when the two tracks are not honouring the pairing distance.
While the specified value will be enforced for serpentine segments note that the actual maximum may well be due to an unavoidable fanout or termination routing which you have placed manually.
Largest distance allowed between two traces