Relative tuning

Zachariah Peterson
|  Created: September 2, 2022  |  Updated: September 7, 2022

Most high-speed interfaces contain parallel buses that operate at high frequencies. For their proper operation, it is necessary to match lengths of the group of signals with some accuracy. Often this length matching must be associated with some timing signal. For example, DDR3/4 memory interface: each eight bits of data has an associated data strobe. Because the data is captured off the strobe, the data bits associated with the strobe must be length-matched closely to their strobe bit.

Length tuning tools

Altium Designer has two tools for tuning:

 - Interactive Length Tuning – for single tracks;

 - Interactive Diff Pair Length Tuning – for differential pairs.

There are 3 patterns available for length tuning: Accordion, Trombone, and Sawtooth.

Xsignals for length tuning

Before you start length tuning, you must create special net classes. After that, they can be used in the length tuning rules. Both net classes and xSignals classes can be used for length tuning. But if we want to apply Relative tuning, only the xSignals classes must be used. You can create them manually or use a special wizard.