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What your Differential Pairs Wish You Knew with Rick Hartley - AltiumLive Keynote

Altium

31K subscribers • 2 videos on Hallway

YouTube
  • Recommended by 5 people: 5 on Hacker News.
  • A classic. People kept recommending it from 2023 to 2026.
  • Presented by Rick Hartley

Intermediate. Assumes working knowledge.

107K views7 years ago5 recommendations

HardwareElectronics

Rick Hartley explains the physics of differential pairs on printed circuit boards, debunking common routing myths and explaining proper impedance control.

Differential Pairs have been used in PC boards for years to carry high-speed signals, in a variety of bus formats. Many Board Designers and Engineers believe the rules for differential pairs are the same in a PC board as they are in a cable or twisted pair of wires. This is NOT the case! This keynote will discuss the advantages of differential pairs, which format gives the best impedance control, what is the right spacing between lines of a pair, what’s important in differential pair routing, and how much skew is really acceptable. Pre-register for AltiumLive next year at: bit.ly/altiumlive Watch all the AltiumLive Keynotes at: bit.ly/AL19vids Follow Altium on Twitter: twitter.com/altium Follow Altium on Linkedin: linkedin.com/company/altium/ Follow Altium on Facebook: facebook.com/AltiumOfficial/ Subscribe to the Altium Podcast on iTunes:bit.ly/altiumpodcast Please subscribe to our channel and remember to LIKE and SHARE. #AltiumLive #Altium #DifferentialPairs

Why it's here

5 people recommend this

What people say. Highly recommended as an essential, intuitive guide to PCB design, signal integrity, and routing differential pairs correctly.

thrtythreefortyon Hacker News • Recommends

On “High Speed Printed Circuit Board (PCB) Design Guidelines”

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.) link to this video
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mordaeon Hacker News • Recommends

On “The Mysterious 50 Ohm Impedance: Where It Came from and Why We Use It”

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) link to this video (What your Differential Pairs Wish You Knew)
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aaronmdjoneson Hacker News • Recommends

On “Vibe-Coding a PCB – surprisingly good”

I have some further video recommendations: link ("How to achieve proper grounding") link ("Keys to control noise, interference, and EMI in PCBs") link to 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.
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dgroshevon Hacker News • Recommends

On “How I leared what a decoupling capacitor is for, the hard way”

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 link to this video
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datenwolfon Hacker News • Recommends

On “PCIe for Hackers: The Diffpair Prelude”

> 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: link to this video
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aaronmdjoneson Hacker News • Recommends

On “The magic of DC-DC voltage conversion (2023)”

> so wouldn't it be better to put power/ground on the outer layers and keep signals in the middle? Signals must never cross a break or split in the plane they're referencing (usually 0V or ""ground""). This creates huge EMI problems. Your proposal would have signals on layer 2 crossing a split in the ground plane on layer 1 (that split caused by power traces). Some interesting material on the subject: link link to this video link link
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foxfluffon Hacker News • Mentions

On “I bought 1000 meters of wire to settle a physics debate [video]”

"I have never in my life length matched the two lines of a differential pair, including at 10 GHz. Never." - Rick Hartley link to this video
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dkbrkon Hacker News • Mentions

On “I bought 1000 meters of wire to settle a physics debate [video]”

> He claims that the way EE is taught is a "lie" The thing is: this is sort of true. Now, all electrical engineers are very familiar with transmission line theory, that's pretty much their bread and butter. And all EEs know that if you're not working with well-defined transmission lines (like coaxial cables), you need to use a field solver. 2D field solvers are often sufficient, but if not 3D field solvers can and will be used. And then most of those same EEs, despite having just used a field solver which clearly shows that all the power is in the fields, which are in the dielectric space between the conductors, persist in using the mental model that electrical power moves in wires. This isn…
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dkbrkon Hacker News • Mentions

On “I bought 1000 meters of wire to settle a physics debate [video]”

> Is there really an epidemic of EE's who know how to use a field solver, but don't know to consider coupling between signal lines? Now, I'm not an EE myself, just someone who took undergraduate electrodynamics, decided to read up the subject, and found some truly excellent videos on youtube. But, at 1:00:23 in that same video I linked before ( link to this video ), Rick Hartley says this: > I spend most of my consulting time solving EMI problems because most of the engineers I meet have no clue about any of this. My job is so easy and I make such a ridiculous amount of money doing it. It's just unbelievable; I solve most EMI problems by simply adding returned vias to boards or changing the positions o…
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MrBuddyCasinoon Hacker News • Mentions

On “The Art and Science of PCB Design”

> But focus on the two most important words in EE: REFERENCE DESIGNS. „I avoid application notes as if they were the plague, because frankly, more than 95% of them are incorrect.“ link to this video
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