What Every PCB Designer Should Know - Return Current Path (with Eric Bogatin)

[@Aemilindore]

I can't stress enough how valuable this content is for the community.

[@RobertFeranec]

Thank you very much Paul

[@abandonedcranium6592]

I agree. I'm just a hobbyist, but now I realize there is a lot of mis-leading electronics information on the internet. People were told information that they did not fully understand, then details were lost when that information was passed on to the next person. If you use a Xerox machine to make a copy of a copy of a copy, you'll have no information left in the end.

[@Aemilindore]

@@abandonedcranium6592 I also watch Phill's lab. It's an amaizing channel too. I wonder if this channel and that could do a combined video.

[@AlexWhittemore]

Agreed wholeheartedly.

[@IanJohnstonblog]

Wow. This was such a kick ass video. Hard concepts explained in a very intuitive way.

[@RobertFeranec]

Thank you very much Ian

[@matteo234321]

My thoughts exactly, amazing representation! Wish I learned many years ago. I mostly do low frequency digital circuits, but for some of the higher frequency communications this could be a life saver!

[@rockydm4266]

Eric Bogatin + Robert Feranec = the best of signal integrity ! thank you!!

[@quickrd2095]

Only 1 years with saw your all video...My Hardware Design skill made 10x better and my company when saw my hardware they made Surprised !...Thank a lot...love you...

[@jacobdavis000]

I thought I knew how to layout a board because I've been gaining experience, but this video shows me how little I know, so far. Thanks for giving me something to sink my teeth into. This is the most important layout video subject matter I've been able to find. I now need to produce a new better layout for my PCB project, after seeing this.

[@alejandroperez5368]

Discouraging is the word for it.

[@RajasPoorna]

Thank you for being such a sweet host. Thank you to the guest speaker as well; he seems like such an honestly sweet learned man. This is all very heartwarming to see such high quality lectures for free. Thank you so much 🙏🙏

[@patrikstaron]

I had this idea in mind since I was 15 years old and told myself that the voltage must gradually get throuth the conductor, not magically be there all at once. Now I finally see the details.

[@JeffreyBoye]

Bogatin is the man! Great choice of guest. 👍

[@RobertFeranec]

Thank you Jeffrey

[@theosky7162]

35:35 ----- Took the rabbit trail to HFSS Simulation and found ANSYS Software. Mind blowing capability, WOW ! My new acquisition and proficiency goal for System Integration of projects. Still newbie, but seems cutting edge powerful to assist designs. I'm particularly thankful for your introduction to Eric Bogatin.In addition to your channel, my path forward certainly now includes : The Signal Integrity Academy. Double thumbs UP ! Thanks and Regards !

[@alyssamaefauni6230]

I think this channel is very under-rated. The information I learned from you are very practical.

[@exoops]

this is because less people are interested in complicated stuff, most people just need cat's videos

[@JonathanDFielding]

Food for thought. One thing you can do to fix a GND return gap, or say if you MUST run a trace over 2 different GNDs, or power planes, is you can couple them together with a capacitor. You essentially provide a High Frequency path for the return current to pass through the gap. It keeps DC from moving between, but allows the return current to continue to follow underneath the sharp edge transition of your positive signal.

[@kentvandervelden]

Absolutely fascinating! Anytime two great engineers have a discussions like this, we're going to learn a lot.

[@RobertFeranec]

Thank you Kent

[@zoebarry1806]

An absolute magic presentation. Designing a PCB is not a simple task as many may think. The schematic is the easiest part. Selecting auto route is probably the worst mistake when working with high frequency signals. There are valid reasons why different PCB materials exist. Thank you, this is a fascinating field on it’s own.

[@Detroit_Playa]

Hobbyist here thank you for the info I've never been to school everything is self taught and videos like this are invaluable to someone like me. You guys are talking about stuff I've never even thought of but now that I've seen it that image of running returns over gaps and all the static will never leave my brain after this. When I'm making pcb's in the future I will apply all of this thank you.

[@glenmartin2437]

Thank you both. Much of this was over my head, but it helped me understand the complexities of designing PCBs and not garbling a signal. Thanks, again.

[@mesmith5706]

wow, I so much appreciate the explanation of the impact of the dielectric thickness (h) in transmission line design.

[@imignap]

Robert thank you for adding your insight at 13:44, this did help me understand the propagation a bit more. I dont see how that interpretations is incorrect either.

[@jarvenpaajani8105]

This is really good. I actually have been struggling implementing 10/100 mbps ethernet with RMII and this video made me realize few bad design decisions on my latest board. Subscribed!

[@awdheshkumarmrt]

Thanks Eric. I enjoyed learning about how we have to dive deeper into the concept of fields to understand the return currents.

[@moseschan6363]

This really helped a lot sir, although i might cannot fully understand the whole video at once but it actually gives me a intuition of how is current flowing through a microscrip line. Thanks for your dedication of works in this video! Especially that current flowing with a gap plane graph, this saved me so much time to understand it! !

[@burievsardor76]

It is difficult to believe that such kind of videos are now available for free. Thanks a lot , Robert. Now because of you i know who is Eric Bogatin.

[@mdchethan]

@Robert, great work, and this whole idea of talking to domain experts and bringing their insights to a larger audience are really really great. @Eric, no words, I can't imagine if someone else can explain signal integrity better than him.

[@RobertFeranec]

Thank you very much Chethan

[@danthomas9624]

It was very helpful with your pauses in the video to give clarifications, Robert! Thank you!

[@3deeguy]

WOW! WOW! This subject is super important. I've built circuits with multiple frequencies such as a microcontroller, with a wireless connection, with a PWM signal, with an SPI module... I thought a large ground plane was enough. I have to consider capacitances, inductances, current wave fronts... l have to put this video on a playlist. Thanks for posting!

[@antecboy]

29:35 is the example Eric gives for 2- or 4-layer board? I can see how it would be terrible in a 2-layer board (no solid GND plane), meaning the GND pour is gonna be a patchwork of copper areas, but in a 4-layer board with a dedicated inner layer as a solid ground plane and the traces on the bottom and top layers it would be fine, as most return currents would follow under their traces and only cross in places where the traces cross, but mostly have their own return current paths?

[@OttoHunt]

Differential pairs returning mainly via the gnd plane was a real eye-opener for me. Thanks!

[@jimmyji8339]

quite clear and slow pace, friendly to beginners.

[@maurozanata]

wow Robert, the videos dedicated to Signal Integrity are very useful. When I read "Eric Bogatin" I immediately put a like. I hope to see many more videos with Eric Bogatin. Other protagonists of these videos I suggest you "Rick Hartley".

[@RobertFeranec]

Thank you very much MauroNzt

[@terratrodder]

I've had a marginal interest in this topic but sure glad this video showed up in my list as now I'm really interested in delving into more! Wish I had instructors like Eric when I was in college, very effective at conveying information.

[@RobertFeranec]

Thank you terratrodder PS: I thought exactly the same, how lucky are Eric's students

[@Electronics_Dreams]

Many times I come back to this video to refresh my memory, really great master class!! Thanks Robert❤

[@carlchong7592]

"Signal integrity lives in the white space of your schematic." Damn. Fourier would be so proud to see these videos.

[@garimagarg2739]

It took me 2 hours to understand the whole discussion. It is worth it. I respect you both. Thank you. :)

[@RobertFeranec]

Thank you Garima PS: Sometimes I still keep learning new things even I have watched the talks number of times before

[@asingh4152]

Robert you are awesome. Appreciate you spending so much time and effort making content for all of us. Thank you!!

[@alvangroen6127]

Great video like many other of you ! All help to improve reliability or fault rate of a product. I have been working on this stuff and related EMC behaviour for a few years. I learned, that the return current for higher frequencies does not look for the lowest ohmic return path, but looks for a return path that will include the smallest enclosed area available. So make a design, which facilitates this 'starting point' ; no gaps, short tracks, good (cable) shielding etc. You improve cross talk, but also minimize susceptibility for external electrical fields by minimalisation of the current loop size (including grounding). In our equipment we improved susceptibility for more than 40 dB for the higher frequencies, which we measured in our own very big EMC test lab. It was amazing to focus on these aspects of electronics, although it is 25 years ago now. Last remark .... a good design needs proper design of electronics, mechanics and interconnections (connectors an cabling). Teamwork !

[@leonardosoliszamora1061]

Thanks to Eric and you Robert, to teach signal integrity to profesional designs. Regards from Chile 🇨🇱

[@RobertFeranec]

Thank you Leonardo

[@vpapanik]

That was an amazing and very enlightening video ! Well done Robert ! I would also love to see more PCB design examples : good practices and bad practices in 4-layer boards, what happens in 2-layer boards and if anything makes sense in one-layer boards. Also how to keep any DC tracks noise free. Keep the good work, thank you !

[@acanadianbear6966]

I'm a CE and they taught us these concepts during our TL and Waves class. Our prof built a pretty nice TL simulator that really helps visualize these concepts. I'll see if I can find it and share it here.

[@acanadianbear6966]

@Gabriel Quijote Hey Gabe! I found the files. Let me know how I can share them. Github I guess?

[@RobertFeranec]

Thank you Gabriel for sharing. A Github link would be perfect

[@acanadianbear6966]

@Gabriel Quijote github.com/gabrielkarras/Transmission-Line-Simulations.git Here ya go lads. Let me know if you come up with any issues.

[@鄭峻杰-i2k]

Robert, thank you a lot. You just gave me a clear picture on how return current flows and where it flows.

[@C0wb0yh3nk]

Wow this was such an eye opener, very glad I saw this. I think anybody interested in electronics should see this video. I have never seen it explained so good!

[@nihar0689]

Hi Robert, thanks for the video. It is always nice to learn from Dr. Eric Bogatin. My suggestion for future videos is that if you could get him to show how to do measurements on a PCB for parameters like cross talk, ground bounce etc. I remember him saying that you need to make sure that the oscilloscope probe does not become an antenna while doing such measurements which is a general mistake that new bees can make. So if we can see him demonstrate how to do such measurements that would be really helpful!!!!

[@RobertFeranec]

Thank you Nihar. PS: Real measurements are on my list. Let's see how it goes as real measurements are more complicated than simulations (the biggest issue would be, that I do not have any good equipment to take the measurements).

[@23lkjdfjsdlfj]

OMG... this cleared up so many things for me. Every student should watch this!

[@vejymonsta3006]

I think it would very valuable if every electronic engineer is taught about electrostatics and the impact they have on electronic devices. A lot of what goes into designing signal integrity with return paths, crosstalk etc. becomes intuitive when you understand how a very dense and very fast impulse forces its way through a design destroying all the barriers you thought were insulative. Generally, we just assume out of college that the impedance between traces is too great to be a concern, but that is only true in limited circumstances.

[@ThePaulus2010]

gotta love this! awesome.. and super you got Eric into this!

[@RobertFeranec]

Thank you Paul

[@pnjunction5689]

Outstanding video! Thank you alot, Robert and Eric! I really enjoy watching these kind of videos. There is a lot to learn!

[@RobertFeranec]

Thank you very much

[@alexistantot7332]

Since the beginning of these videos, I check almost every day if a new one has been published ! I have read about these concepts many times, I tried to apply them as much as I could in several PCB designs but it is the first time that they start to all make sense together in my head. I'm super curious also about the test boards he talks about to illustrate those principles ! Thank you for the videos :)

[@RobertFeranec]

Thank you very much Alexis PS: I also made a note about the boards ... if it will be possible, I would be very interested to make some videos from real measurements.

[@konstantinponomarev1087]

Hi, Robert. This video convinced me to enter to Eric’s SI class. Thank you

[@nyaaark.5121]

Hi robert! I am an engineering student, I would like to thank you for providing us great content! This was very helpful! Thank you!

[@BB-me9po]

Great video as usual, Robert. I read a paper somewhere that you can help mitigate the effects of cut planes by carefully placing capacitors ACROSS the gap. If the gap is on the ground plane beneath a signal on the top, the signal line would reach the location of the ground gap and right where that gap occurs, you plant a capacitor on the signal line on the top plane that allows the signal to continue. Somehow, that capacitor helps to minimize the effects of the gap on the return current. I am curious if you could investigate this in the future and determine how effective it is, or how ineffective it is. Thanks.

[@RobertFeranec]

Thank you B B PS: I read the same

[@rakeshv46]

Yeh...in advanced layout course, mr.Robert mentioned about stitching caps....I am also curious if you make brief in future videos....

[@abc1w]

Your videos are amazing and inspiring at the same time; to go a step ahead in learning more about PCBs. Eric's talk has been an eye opener towards practicality of how a transmission line works and in his words "there's a lot to signal integrity".

[@djadostyle]

Very very interesting as usual, now we (you) are moving more deeper in concept and I'm happy to see more and more participants. Great idea to get others experts involved. Maybe Dr Rick Hartley next time ? Thanks you Robert !

[@annacersongor8553]

Very Informative video, especially with the contribution of such a great figure as mr. ERIC BOGATIN. We are waiting to see more . Thanks a lot for sharing.

[@RobertFeranec]

Thank you Annacer

[@zhitailiu3876]

"It’s all about the space 'Bout the space... space... space... space"...... as Dan Beeker sings :) It's a good exercise to use this dynamic intuition to think about how the return current (energy) is built up when a track changes layers through vias. Good video as always! Thanks, Robert.

[@RobertFeranec]

Thank you very much Zhitai

[@Hadi-zw9mb]

Nice video and explanation. At a very high frequency, something completely different happens in coupling and crosstalk.

[@fireblade31967]

Thanks a lot Robert and Eric. Very Nicely explained, very nicely laid out presentation. The visuals are awesome, kudos to the person in Japan. I learned a lot from this today.

[@hightechsystem_]

Please keep doing your video interviews.. they are so valuable.

[@ats89117]

Best video ever! Very informative and will be getting much more material of Eric's to learn from. Please have him back if possible to finish telling us why copper pours can be the worst thing ever! I never heard this before, and like many people, I use copper ground pours everywhere...

[@RobertFeranec]

Thank you ats89117

[@NiteshKumar-ss4gg]

Appreciate your effort and the way the terminologies are explained. Really loved it

[@7th_dwarf542]

excellent topic and speaker. I wanted to learn about retun signals in differential lines recently. This video made me raise my eyebrows.

[@michaelmichalski4588]

That's really cool. With the differential pair over a ground plane you can see why it has a shielding effect. It's not so much that the fields cancel, they do, but that doesn't really describe all of what's what's happening. There are lots of ways fields can cancel. In the case of a differential pair over a ground plane, it has a lot of quadrupole charachter. The monopole and dipole terms will be there, but reduced and the quadrupole term will fall off rapidly. This has implications for optimal spacing of the conductors. Without the ground plane you have more dipole and no quadrupole.

[@Yreq]

This video had opened my eyes, while blowing my mind. It gives me a bit of understanding of phenomenons that stands behind some electronic aplications obserwed in real life. Your video helped me to join some loose dots🙃

[@adilmuhammad7911]

Unlearn what you have learned. Thanks Robert & Eric for doing such a great job. You people are amazing . :)

[@rajendrarathod351]

very much valuable content thanks to Mr.Eric & Mr. Robert

[@prototype7970]

I am only a beginner un PCB design but it very interesting video. Thank you for making them easy to understand !

[@Katupiry]

Wonderful video. Cemented various concepts what I had only visualized in my head.

[@RobertFeranec]

Thank you very much Katupiry

[@arthurfarias9550]

I always think as a lightning h strike. The field propagates stablishes. There is a path to currents flow and current flows in the easiest path. 😀 It flows more in the lower impedance path. And distributes through the conductor once it isn't perfect. But mostly at the surface.

[@vyacheslavten708]

Thanks for your videos, it really helps me to increase my understanding when designing PCB.

[@BeMuslimOnly]

thank you Mr. Robert and Eric Bigatin. it was very useful

[@georgemallard4120]

Eric is a master at explanation!

[@brus54per]

Very, very interesting discussion! Thank you to you and to Eric!

[@RobertFeranec]

Thank you very much sm6eik

[@spacewaves94]

Love these videos and the call format, high quality stuff

[@shubhangigurudiwan1753]

This video was really helpful. Thank you so much. I have a question though. If you have a power plane also right next to this signal line, will equal amount of displacement current flow through that also? (Since that plane is also seeing the change in electric field). This would mean that there should be both a power plane and a ground plane adjacent to all signals with no cut in them?

[@gankankg]

Great video !!! Thanks to robert and eric, looking forward to more such videos

[@RobertFeranec]

Thank you gankankg

[@modulate72]

Thanks Robert, these videos are pure gold.

[@st3ddyman]

Finally I understand it! Many thanks to you both

[@RobertFeranec]

Thank you very much Stephen

[@moienm8802]

This was an awesome presentation. Thanks Eric and Robert.

[@changyiful]

Thank you so much to share this discussion for me. Only one thing I'd like to notice is that the talking of differential pair return path wasn't finish. I'm eager to know what's going on if we pull differential pair far from the reference ground plane.

[@andredevilliers0]

Hi Robert, thank you very much for creating these informative videos and also thank you to your guests for sharing their knowledge. I always want to learn more to improve my pcb design skills and understanding of electronics. I really appreciate all the effort that you put in. Always looking forward to your videos. Kind regards from South Africa Andre

[@abhishekupadhyay3419]

Thanks Robert, this is very nice video with the 'Eric Bogatin', I liked your interruption, they were on point.

[@RobertFeranec]

Thank you Abhishek

[@guillep2k]

Super video!!! I liked you 100 quick tips video series, but this series is superior!! Thanks, Robert.

[@RobertFeranec]

Thank you very much guillep2k

[@georgechatzidakis3111]

Congratulations to both of you Robert and Eric! Great video! Robert continue this kind of videos!

[@RobertFeranec]

Thank you George

[@jacewalton6677]

Nice! Helped me understand the importance of the ground plan

[@sandeepkumartutiki851]

Absolutely quality stuff..thanks Robert this was really brilliant conversation..please make more such content.. eagerly waiting..

[@lizard101pwd]

Great video! What I am really interested in is. If you have a multilayer board with Power plane- signal plane - gnd plane. Is there any return path over the power Planes as well? If you consider that at high frequencies GND and PWR are shorted by bypass capacitors? If so then it might be a problem splitting the powert planes as well (for multiple sources its necessary). So for good signal integrity one would need to avoid stackups like this.

[@theminertom11551]

In the video with Eric Bogatin "what every PCB designer should know - return current path" at about 10:50, Eric mentioned Maxwells 4th law and the displacement current, as the means by which the signal flows down the transmission line and returns down the return path to the source. However, my understanding of the displacement current part of Maxwell's 4th law is basically that the curl of the magnetic field is the result of the changing electric field. It is also my understanding that a current does not pass directly through a capacitor. Yes, I know that in the transmission line representation there is not a "real" physical capacitor but the transmission line is a representation of an infinite amount of infinitely small capacitors across the dialectric (between the signal and the return). Not that I wish to argue with Eric Bogatin, but if there is no actual current flowing through the dislectric then the only current in the return path is caused by the curl in the magnetic field which is the result of the electric field change. This would make the animation somewhat misleading. Perhaps the animation would be less misleading if it could show the return current in the return plane being generated by the curl in the magnetic field. I hope that someone can clarify my understanding of what is actually happening. Thank You Tom

[@robegatt]

A current DO pass through a capacitor, because there is a movement of charges around it. It only is a different type of current. Check how displacement current fits in the capacitor paradox in maxwell's equations.

[@giannisasp1208]

Really good stuff Robert. Eric Bogatin has a great and unique way of explaining things in a simple and accurate way! I would have been extreamly lucky if he was one of my teachers.

[@debasish2205]

Thanks for this in-depth video. Keep posting. Thanks to Eric🤗

[@TooHear]

Very interesting and intuitive material. But I'm particularly curious on minute 17:00, when talking about the current going around the gap: Eric mentioned the current going around the gap is some kind of simple approximation, but in reality the energy excites a slot wave mode in the gap. Any article or text I can read about to understand this mechanism?

[@jack_brooks]

Hey Robert, in your 3-trace split ground plane simulation (31:05), there is regular ripple pattern on the return current path around the edge of the cutout. I'm wondering if that is constructive interference of all three of the return traces return currents at 1MHz. Can you measure the distance between those ripples and see if that matches the wavelength of 1MHz? Also, the distance between the traces at the cut appears to be a multiple of the ripple.

[@RobertFeranec]

Interesting. I am planning to go back to these simulations after I know a little bit more about what everything ADS includes in the simulation and when I play with 3D field simulations.

[@JesusSoonComing]

Robert, you are the best! Keep up the good work...

[@pizzabeerengineering2488]

Great video, thanks. The voltage wavefront model is interesting. di/dt is a concern in high speed but also high current. Would be interested in a similar discussion about power supplys

[@devdattchattopadhyay5380]

Great video! The concepts are very well explained. Thank you Robert and Dr. Bogatin!

[@shmani6992]

I definitely learned a lot from this video. Thanks a lot both of you. Eric Bogatin you're awesome.

[@danmarquez3971]

WOW!! This was a great video that demystified a lot! THANK YOU!

[@Nik930714]

Really nice video. I really should show it to my boss, every time i argue we should add more layers to a board.

[@gpetters]

Thank you to explain in detail this very important topic! All the effort you put in to educate manu of us is invaluable and highly appreciated. Your videos are excellent. Stay safe, and continue all the good work. Cheers from Norway.

[@RobertFeranec]

Thank you very much gpetters

[@jrjr54321]

Hyhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhyy h hh h h. H hh h. H hh hhhhhhhnhh. H. i

[@ParameswaranKF]

It was a very informative video. Eric explained the stuff quite well from theoretical as well as practical aspects of PCB design.

[@MaxWattage]

Dear Robert, I have a wild suggestion for reducing digital crosstalk. Instead of having two side-by side digital tracks running over a contiguous ground plane, why not have a separate ground track for each one located on the "ground layer", that takes the exact same path as the signal trace. (i.e. you cut-and-paste the signal layer tracks onto the "ground layer"). The signal's EM wave would then be more tightly constrained to propagate through just the dielectric located between the signal layer track and its dedicated ground-layer track. I feel that this should act to significantly prevent the return currents from two nearby signal tracks from mixing together and causing cross-talk. I would love to see a simulation of this idea. Obviously for the high current return-paths from IC power pins you need a contiguous low-impedance ground plane on one of the deeper layers of the PCB, but for those high speed signal tracks where crosstalk is an issue then I feel that the ground reference for those tracks would be better implemented using individual ground return-path tracks.

[@RobertFeranec]

Dear Nicholas. I am not really sure what would happen ....

[@davebing11]

It could work if both sets of traces are the same electrical length and see similar disruptions. One of the key principals of differential traces is to reduce the odds of one trace seeing something different than the other trace so that any disruptions are common mode and not differential.

[@AbdullahKahramanPhD]

I don’t know why, but our community became really educating recently and I am not complaining at all 😅

[@RobertFeranec]

:)

[@danialphaomega]

Efficiency, thermal dissipation, even RFI play a part especially when its a multi layer board. Also many radio operators are plagued with displacement currents

[@shravanmalagihal1229]

Very Interesting video. Thank you for this great one. Please continue with much more.