Altium
5 HN recommenders · recommended in 8 months, 2021–2026
1:03:22 · 108K views · Oct 24, 2019
Rick Hartley's AltiumLive keynote on differential pairs in PC boards. He argues the rules from cables and twisted pairs do not carry over, and covers which pair geometry gives the best impedance control, the right spacing, routing practice and how much skew is acceptable.
HN engineers cite Hartley as the intuitive, field-based alternative to cargo-cult PCB advice, especially on differential pair routing, reference planes and EMI.
10 comments from Hacker News
The article is not that good, but whatever. I am new to electronics myself and quite fascinated how has the art progressed in the past hundred or so years. There are people remembering "we were doing it wrong". Incredible. Anyway, if you are interested in signals traveling inside those cute green multi-GHz boards you make your living off, go watch Rick Hartley. [LINK] (How to Achieve Proper Grounding) this video (What your Differential Pairs Wish You Knew)
I found Phil's lab content [1] [2] indispensable for just this. Phil is a great communicator and gives in-depth explanations, so I didn't just watch most of his youtube, but also bought his mixed signals course and was very happy with it. Phil also recommends this lecture in one of his videos [3], which is still one of my all time favourite lectures ever. [1] [LINK] [2] [LINK] [3] this video
I have some further video recommendations: [LINK] ("How to achieve proper grounding") [LINK] ("Keys to control noise, interference, and EMI in PCBs") this video ("What your differential pairs wish you knew") [LINK] ("Secrets of PCB optimization") These are all by Rick Hartley (from GP's comment) and they are all worth watching in this order.
Basically, go watch every Rick Hartley video on YouTube. He is awesome at explaining. It will become intuitive instead of being a bunch of cargo cult advice. (Normally I dislike long videos but this is absolutely worth your time if you design PCBs.) this video
> First off, you want to keep both of the pair’s signals close to each other throughout their length. The closer the two signals are, the better external interference cancellation works, and the less noise they radiate (…) Wrong! This is a myth that's stubbornly difficult to weed out. The coupling between the wires of a pair is only ~12% the amount of coupling to the reference plane. On a PCB it's best to treat each signal on its own and route it as a single ended, coplanar waveguide surrounded by reference planes. This allows to use far thicker widths, which reduces inductance, which also reduces the coupling to radiating EM fields. If you want a longer talk on the topic: this video