PCB Layout & Decoupling - Explained why it's so complicated (Part 1)
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- Опубликовано: 9 сен 2020
- Change the way how you look at powers on your board.
Part 2: PCB Layout & Decoupling - Understanding Impedance
• PCB Layout & Decouplin...
Part 3: PCB Layout & Decoupling - Measuring and Fixing
• PCB Layout & Decouplin...
Big THANK YOU to:
- Florian Hämmerle www.linkedin.com/in/florian-h...
- Eric Bogatin / eric-bogatin-368860
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Who we are?
PCB DESIGNERS
What we want?
PART TWO OF THIS VIDEO
who we love?
ROBERT FERANEC
:D
can't agree more hehe
There is no need to be embarrassed. Going from the knowledge you gained from books, slides, lectures and whiteboard doodles to using it in practice is very often a "connecting the dots" moment and it's not so unusual to need an example, some hand holding, or just extra time to think about it before it all comes back. Great video as always, thank you very much.
For those interested in high speed processes happening on your PCBs I would recommend reading Howard Johnson's books "High Speed Digital Design: A Handbook of Black Magic" and "High Speed Signal Propagation: Advanced Black Magic". After these books you will clearly understand what is happening on your PCBs.
Agree . The best purchase i have ever made .
I remember reading the high speed circuit designs...definitely worthwhile
Will check it out. Thanks for the recommendation.
Bogatin's book are better imho for this particular topic
It is only math, not a book for hardware designer
That’s some ultra high quality content! Thank you!
Thank you very much nenharma82
Great job Robert
Your Humility and passion for continued learning make you a true educator
Thanks Robert for putting all of these things together is such a manner! After working on PCBs so long it's easy to start thinking about things in a given way. It's so good to see the tools and experience of others show that this may or may not be the correct case! You've given me more than one epiphany if your videos. Thanks!
Fantabulous ! There is no word which can express my feeling. Great job Robert !
Thank you for leaving in the video with Eric. It was a great refresher for myself as well, seeing the tank circuit, I recognized it and understood more clearly. Excellent video! We learn from our mistakes.
I love your honesty and willingness to ask questions to get to a better understanding.
This video is an excellent combination of theory, measurements, and quick calculations. It is also a great reminder how important it is to try to gain an intuitive understanding of a design and its performance. Thanks!
Robert, I need THANK YOU so much for this video series! I've been waiting for these explanations to show up in RUclips since 2010. This will help us understand everything from decoupling, ground loops, EMI, etc.; all the black magic stuff of PCB design. I'm very happy I finally get to watch this.
Thank you guillep2k PS: That is the reason why I am making these videos. There are some pdn videos on the internet, just ... it's not very easy to understand the topic. Many videos are too advanced or require some other knowledge to understand them properly. So I am trying to make a video which would be easy to understand - but as it is complicated topic I am not sure how successful with the explanation I will be. Let's see what people will say ...
Thank you, invaluable information. Very generous of you all for putting this together for the community. I'll share around.
Looking forward Part II
Thank you very much
i've been watching you're videos since my first year of my engineering bachelors until my final year , i'm very happy to see that you become THIS successful on youtube !!!
OMG! I was just about to start placing bypass caps for my PCB and this showed up! Can't wait for the next part! :)
Thank you hri124
Great video tutorial Robert, I can't wait to see the second part!
Thank you very much Edgar
Thank you Robert! With yours channel and yours curses I’m learning a lot. You are a very good teacher. Please continue yours great work.
Thank you very much Jorge
Hi! These videos are really, really interesting and useful. I am discovering a new world in the design of PCBs. Thank you so much to Robert, Eric and Florian for the content, It is highly appreciated! Great guys and teachers :)
Well done Robert, really appreciate the time taken to do these!
Thank you very much Andrew
@Následovník Nikoly Tesly Slovak
@Následovník Nikoly Tesly :D
Hello Robert, grate video about decoupling & power supply! I'll be waiting for part 2 eagerly. Thanks!
Thank you
Cannot wait for the second part!! Great video. You have gone straight to the guru on signal and power integrity - Eric Bogatin. I just got his latest book on SI integrity. Great read
Thank you Jayakrishnan
This is so amazing! thank you. Cant wait for next part. Everithing is informative and it is always great to look and refresh the basics. NO shame in that :)
Thank you :)
Wow, We've just almost built an oscillator accidentally!!
Really really precious video!!
The step response looks really awful. Can't wait to see a revision of the board,
like adjust the capacitor values, modify the power connection(try a 4-layer board) , and perhaps remove the bead(?).
Please upload the second part! Can't wait to see it!
Thank you Zhitai
I was on the edge of my seat most of the time.
It always struck me, that the best teachers are the people who just learned someting new. If there was a complete series on electronics made by a novice, where he's explaining stuff as he learns it, it would be the best course ever. Add a few comments from his mentor and you have a solid education.
I feel it the same way.
No...
really premium content. you clarified a lot of doubts I had... Thanks..!!
Big thumps up for taking a stab on illuminating the dark messy world of PDN. Bogatin book last chapter is probably the best intro on this subject.
The most simple method is to draw the return path of each signal/current, try to minimize the overlap between sensitive signal and noisy tracks. Always place the decoupling cap close to the chip.
Thank You Robert for your efforts.....excellent concepts.
Well done Robert 👏 brilliant video. Very interesting and educational discussion relating to PDN. I'm looking forward to watching the follow up video.
Hi Robert,
I definitely want to see the next part of this video. What I really like about this video is the collaboration of the different area of expertise that you are bringing together for us. For instance:
1) The board from your PCB design course which teaches us how to make the best use of the PCB layout tools and follow best industry practices, 2) The simulation software that you used and showed us how we even we can simulate our own designs if given the right tools.
3) Last but not the least, how you compare simulation results with actual waveform captures from oscilloscope and then bringing the expertise from Dr. Eric Bogatin who looks at circuits way differently than others given his background in physcis.
Keep up the good work Robert, it is really educating young engineers like us.
Thank you very much Nihar PS: After making this video, I may need to do some improvements on the board :D
Thank you all so much for explaining, after watching this video (part 1), you let me realized that even though the microcontroller is doing the switching (on and off), this situation can cause the microcontroller's voltage supply "Vcc" pin to fluctuate (having voltage ripple in millivolts), where the voltage across the microcontroller can become low depending on how large the "Power Delivery Network" (PDN) impedances is.
You also summarized the 3 things that you've learnt, which is the key take aways of this video❤️ love your videos, Robert, Florence, and Eric🙌
sure we want the 2nd part of this video. this is really important and amazing
Thank you Blu PS: Part 2 and 3 are now available, there still should be also at least part 4
Escribire en mi idioma NATAL, muchas gracias Robert por compartir tu conocimiento, nos motiva a los que amamos esta carrera a seguir comprendiendo las hermosas imperfecciones de la Electronica.
Thanks So much, for you Work.
Regards from Perú
Kudos Feranec..
Very Informative and explained them in a practical way..
Also making industry PCB design experts part of your lecture.
Thank you very much..
As a nerd myself, this phrase (and the fact that I felt it so true) made me feel very proud: "and this is where the fun begins"!
:)
Thanks Robert as always loved this video as well. Appreciate your efforts to make us educated about some really difficult concepts.
Thank you very much Chethan
Thank you Robert for this amazing video. I have some idea that the power rails is a problem. BUT, never imagine that the problem is huge like that. Sure, continue with this parts, every parts you need to explain
Thank you very much Pablo.
Great video - to get insight from Eric Bogatin is a real treat . World expert with humility ! . I used your cadence course some years ago which saved a ton of time 👍
Thank you Hedley. PS: I am very happy you found the course helpful
Surely fruitful! Thanks!
You asked if this video is useful? It is absolutely jaw droping! It is mind blowing! I'm very very anxious to see the next part! You have no idea how much information you put there, like you said, "why they don't teach this at school?"
Thank you very much Xtian for nice words.
bro u can be younger than me, but u dont have to separate
out your knowledge without money! u r the master of this event. m also altium designer, but u r awesome mate
from that starting part of the noise and its effects I can see that everything we learned in the school is very important but why they didn't tell us the applications and its necessity to our further work in design
many thanks to you Robert for your efforts and keep going bro
Thank you Amr PS: I agree
This really helps me to look at systems from different perspective. Great video. Regards from Trenčín.
Thank you. PS: Tak so sa mozno obcas aj stretavame v meste
Really great Video.
Looking forward for the next ten parts ;)
Thank for the lot of work you put into it
Thank you very much PS: Thank you also for noticing it is a lot of work. I checked yesterday, it's been actually 5 months since I started working on this video! WOW time flies
thank you for sharing this video, very helpful!
Fantastic video, as always! I wish I had access to such high quality learning materials when I first started working on high speed designs. Never too late to learn though :)
I wish the same! :) Thank you.
Thank you so much sir for explaining this important topic.
Robert, really great video... Thanks for it...
I loved the vídeo! Can't wait to see next part
Thank you Leo
Thank you so much for this explanation and demonstration, Robert, Florian and Eric ( no disrespect meant by omitting your surnames ).
I thought I would not need to be this careful about switching noise at low frequencies and it's mitigation with decoupling capacitors. I have been so wrong and I stand corrected, but my curiousity about how this works is also awakened. Thanks again!
What an awesome video! Thanks so much🙏
@Robert Thanks for making this video! It has been 25 years since college so there was a lot in this video that was new to me. We did not have that kind of advanced software to run our simulations with. Mostly, it was by hand with a good calculator. Anyway, I enjoyed this one and I definitely want to see the next one.
Thank you for watching and leaving feedback wrekced
Learned a lot! Thanks Robert
Thank you Raza
From every video, something or the other new concepts are being learned every time.
Thank you Aniket. I am very happy you found the videos useful.
@@RobertFeranec Yess Robert your videos are very insightful.
I'm very interested in all of this. You are helping me understand some of the mysteries that can sometimes bite me in the... !!!
Thank you Roger
Eric have change the world
That was an awesome video! Many many thanks!!!
Thank you very much Andriy
Well Done Robert!
Everything about your videos is great- the content, the pace of content delivery, the thought flow, the end results and its interpretation. Thank you so much for doing what you do! Your videos help us join the dots on everything we learnt in school.
very good lecture... so informative and practical.
Thank you yusie
No one has every subject mastered. I say we're born with faulty DRAM built in. We regularly need to manually reset the refresh rate and often start over.
I was in the same boat as you when Mark asked you those questions. I was thinking, 'I should know/remember this,' but honestly didn't at the moment. It's okay though. I know I need to grab The Art of Electronics off the shelf and look in the first few chapters for my answer.
Thanks for sharing.
Thank you. PS: Yes, I had to refresh a LOT of theory when working on this video.
Wow, thanks Robert! I had heard a lot of the theory before, but felt like I never could connect it together in a way that I could practically use it. This video helped a lot with that. Thanks for the moment at the end where you summarised the 3 things you learned from Eric Bogatin. That summary helped a lot too. My head is still spinning though ;-)
I am eagerly looking forward to the next video. I hope you will be able to show how to put all this into practise when we design our circuits and do layout. For me that's the part that eluded me so far: how to bring this complex theory into day-to-day practise?
Thanks again for your efforts and explaining it to us!
Thank you very much Christe4N
Unfortunately I cannot add one million likes under this video. Waiting second part. THANK YOU Robert!!!!!!!!
Thank you very much Andrej
These are amazing
This guy's humbleness keeps amazing me again and again... An anecdote: I'm a power electronics guy and have worked with high voltage converters. So I used to design and build high frequency high voltage transformers all the time and measure the transformers parameters with the help of an impedance analyzer. I've developed reasonable experience, but the fun (sad) fact is: I had never thought of PDN this way! I guess we end up ignoring the basics when we're faced with a complex problem sometimes... Thank you for all the content!
Thank you Andre
excellent video robbert!
Thank you very much Paul
Thank you! You are the BEST!
Thank you Kemal
very informational ... TY for sharing ... more please .. cheers :)
Thank you very much Tim
Btw. Love the Fermi type of problem solving from Eric Bogatin.
Great content...thanks for making these videos
Thank you very much
@@RobertFeranec hi there is no explanation why Eric considered only the first LC loop for very high frequencies? Could please upload the whole video call of you with Eric. Or could you please complete the explanation for the pdn graph from low frequency to high frequency. You did not continue Eric explanation after 47min. Please upload complete explanation. Thanks
@@santoshgurral66 It is explained in the next part. Basically, for some frequencies some of the capacitors will behave as a short circuit (or inductor) - so it is not important what is connected behind these "short circuits".
Great video. Thank you
Thank you Martin
Very nice video, TNX
Wow, this is really good content! Thanks for opening this large can of worms :-) I'm really excited to see the next episode!
Thank you very much
Thank you very much.
And don't be embarrassed it's been 5 years that I left university and remember nothing of these because of time I focused on embedded systems.
It happens to all of us, we focus on one thing and forget the rest.
Thank you Amir
My god this video is so helpful, thank you so much
I want to see second part pls. It is really usefull. Thanks for your videos
Thank you Freddy
Good video. I really enjoy every of your videos robert. As I am currently writing my master thesis I have to add something: Everything about decoupling you told does not apply to multi-layer boards as the inductance is almost non existent by the use of vias and power planes, rather its more about reducing the length of the trace in order to transmit faster waves with lower wavelength without reflections. That's why high capacitance values like 4,7u can be placed almost everywhere on the board when designing 4+ layer board :) Best Regards!
thank you Oizys. PS: we will speak about this in one of the next videos. I already have recording of this topic from my call with Eric, I just need to process and prepare the video.
Thank you so much!! i learned a lot as well haha
really good work
Thank you Ron
great learning
It's no wonder so many MCU datasheets recommend connecting decoupling capacitors directly to the power pins (NOT through vias) with the shortest traces possible. Having a PDN characteristic low impedance is neat, but better to suffer a few ohms and have a flat impedance profile. I was familiar with processes for measuring frequency response of the PDN with instruments for that (I'm guessing you will reveal in future videos), but I hadn't considered the remarkable DIY approach you show here. Thanks Robert
Thank you Greg. We will mention flat impedance in next video(s). And yes, Florian will mention how we measured it - we used Bode 100 ( www.omicron-lab.com/shop/Bode-100.html ) and a probe which Steve Sandler from Picotest borrowed me ( www.picotest.com/products_index.html )
@@RobertFeranec Yay! Exactly the method and tools and expert advice source I had in mind.
Bro please keep making more videos 🙏 for us that can't afford a master's degree, you are our open free university
Please upload 2nd part, very interesting and eager to see
Thank you Harish
I liked that @46:00 was left in, reminds me I'm not the only person who can get confused on a question when we really do know the answer haha. Like a simple question but we think its something else. Although I could understand why because I wouldn't be thinking about impedance graphs like that when talking about traces and thinking about other things like resonance and self resonance.
Stupendous!!!
Thank you Simon
Thank you,we waiting other video
Thank you Emrah
for future video, i hope you can make some discussion about this important topic for more specific application, in this case, the microcontroller running in lower switching, for example in motor application where the switching output (PWM) usually around 20 kHz (not in range of 5 MHz as shown in video).
Advising you to see Eric's PDN webinars in his site. he explains this subject great!
Thank you so much Robert, I like you very much :)
Thanks Mr Feranec, great video again. Of course, such videos are really useful I would appreciate if these kinds of videos keep coming. Moreover, we always want to learn new things and refresh our memories from time to time. What is more, for the noise we see at the VCC pin can it also exist at the ground? Can it affect the noise level especially at mixed-signal boards?
Hi robert,
You can understand pdn from eric bogatin book to understand how this decoupling nw is designed and works.
Interesting. Please do second part of video.
Thank you Adam
Thank you
If you put large capacitors right at the USB power input it is recommended to use some form of inrush current limiting.
Great video.
I have not looked up the exact parts used, but I suspect the discrepancy in resonant frequency of 30 kHz vs 60 kHz likely comes from the reduction in capacitance as DC voltage is applied over that physically small 10 uF ceramic capacitor.
Small ceramic high-capacitance tend to have a very strong dependency, sometimes with the capacitance reducing to 1/10 of the rated capacitance (!) when at rated voltage. Most types except C0G are affected.
Also the inductance of the ferrite bead could decrease with increased DC current. Possibly by a lot.
If these effects are not taken into account in the simulation models, the real resonant frequency will be higher than the simulated as both the inductance and capacitance are lower at the real operating point.
Robert you crawled for us to walk, no worries!😁
Wanted to make a "quick" video about decoupling capacitors. Oh how I laughed ! I recommend Signal Integrity Simplified by Eric Bogatin. Saved to watch later.
Yeah ... I know now .... it's not so simple :)
@@RobertFeranec Whilst at Nokia, I developed a Xilinx based FPGA board for camera image manipulation development. My boss at the time was very unhappy that I had spent a whole three days working out the decoupling capacitor network for the board. I pointed out that the design would have a PDN impedance of under 0.1 Ohm flat upto 800 MHz and that he'll be able to switch all the outputs simultaneously on/off without the device glitching.
I used Agilent ADS 2010 back then and modelled each capacitor as a combination of series RCL and parallel R lumps. The data was provided by the detailed AVX datasheets.
Xilinx provide a very good application note for "Power distribution system design: Using bypass/decoupling capcitors" ref XAPP623
@@BobBeatski71 Nice!
I am waiting for next part
Thank you rahul
Thank you!!!
Thank you Pham
Robert,
Nice work with Florian and Eric.
I would like to suggest some vocabulary. The waveform that the switching load forces onto the power supply nets is best called "interference". It is a signal that will mix into other loads sharing the same power supply and interfere with the expected signals there.
I would reserve the word "noise" for non correlated and unpredictable disturbances such as, but not limited to, the thermal excitation in conductors called Johnson Noise.
This distinction is helpful.
Next the series elements in a power supply network should be called "Decoupling beads" or even "Decoupling resistors". These elements decouple one interference source (one load) from another (other loads also known as other victims). They also decouple the capacitors near the load from the distant and usually very large capacitors in the power supply which prevents typically the lowest frequency ringing in a power supply distribution.
The capacitors to ground on the power pins of a load should be called "Bypass capacitors" . They offer a low impedance path for current between the power pins of a load and the ground pins of a load and the current the load consumes comes from them in proportion to how easy it is to flow (You have to think conductivity here).
This last sentence shows why it becomes insightful to think of the currents that flow as the load is active. It is providing this current to the load the bypass capacitors are doing.
The current bypasses the power distribution network and stays local to the load and it's bypass capacitor(s).
At high frequencies the load current is supplied by the local bypass capacitors and they (the bypass capacitors) are recharged only at lower frequencies through the decoupeling components of the power distribution network.
For good electromagnetic compatibility you never want high frequency currents traveling a long distance over power networks. To have high frequency currents traveling over long distances is to build a magnetic loop antenna which couples interference into adjacent circuits and even perhaps outside the product where your friendly FCC compliance people will measure them (thus causing you to have to revisit an FCC test after design changes).
Sage advise I learned from a mentor. "Never use more bandwidth in any circuit than you need for that circuit's proper operation." So for example put a 1K resistor on all of your UART TX and RX nets cause they are going to be very sloooow compared to the typical processor clock. And for best effect the resistor on the RX line should be near the level shifter not the processor. Do you see why?
I hope this helps.
(Forrest) Lee Erickson
Physicist who pretends to be an electrical engineer.
Would like to ask Florian if he has placed the Arduino sketch (that he used to operate the DUT at the various frequencies) somewhere public?
Although I do not have a Fedeval Arduino I have some out of China with a QFP processor and the bypass capacitors are quite distant from the controller. Would like to measure my DUT.
Thank you very much Lee
@@forresterickson6225 Lee, here is the code:
//storage variables
boolean toggle = 0;
void setup(){
//set pins as outputs
pinMode(0, OUTPUT);
pinMode(1, OUTPUT);
pinMode(2, OUTPUT);
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
pinMode(11, OUTPUT);
pinMode(12, OUTPUT);
pinMode(13, OUTPUT);
pinMode(14, OUTPUT);
pinMode(15, OUTPUT);
pinMode(16, OUTPUT);
pinMode(17, OUTPUT);
pinMode(18, OUTPUT);
pinMode(19, OUTPUT);
cli();//stop interrupts
setInterrupt(159); // = ((16*10^6) / (frequency*2)) - 1
//50kHz = 159
//60kHz = 132
sei();//allow interrupts
}//end setup
void setInterrupt(int divid){
TCCR1A = 0;// set entire TCCR1A register to 0
TCCR1B = 0;// same for TCCR1B
TCNT1 = 0;//initialize counter value to 0
OCR1A = divid;// = (16*10^6) / (freq*2) - 1
// turn on CTC mode
TCCR1B |= (1
I'm surmising at high frequencies that the other down loop inductors become unimportant because the nearest capacitor starts becoming the path of least reactance for the current. Eager to see the next video to find out.
Thank you Jack