Differential trace length matching

[Jhuffaker]

So I'm brand new to PCB layout thanks to my first engineering job and need some advice on length matching of differential signal traces. While I have been given some training on using Altium and my education lets me handle the circuit design, but I am still a little lost on length matching for differential signal traces. I have been finding some conflicting information on how to length match a pair. I have found several guides on the subject of routing differential signals and the two that stood out to me were one from Texas Instruments and a second from Toradex. They have one image that conflicts with the other and with what I thought was true of handling a coupled pair. The two images attached show a general guide to a sawtooth pattern used to extend the length of the shorter trace, however the inequality signs are obviously contradicting. Normally I have found TI to be pretty good with guides but theirs seems to be opposite of what I thought. If anyone could clear this up for me it would be very helpful.

Aside from that, I've read that sawtooth patterns only add up to about 30% of the length of the portion of trace it is applied to. I have also been told conflicting things about using sawtooth over a single longer trombone pattern to extend the length all at once where the space will allow. What do you guys recommend using? Can anyone provide any further reading on the subject?

[thm_w]

Might want to link the note in question: https://www.ti.com/lit/an/slla414/slla414.pdf

I can't see why it needs to be greater than here, this onsemi note also agrees with the 'less than' guideline: https://www.onsemi.com/pub/Collateral/AN-6103-D.PDF
But it depends on the design requirements, they may not be strict so you could get away with a really wide length match bump.


https://www.altium.com/documentation/18.0/display/ADES/((Length+Tuning))_AD#!LengthTuning-LengthTuningDifferentialPairs
https://www.ti.com/lit/an/spraar7h/spraar7h.pdf