How to Successfully Design Your Power Delivery System | Lee Ritchey

Guests Lee Ritchey | Uploaded : 28/05/2024

The EEcosystem Podcast

How to Successfully Design Your Power Delivery System | Lee Ritchey

In this conversation, Judy Warner talks with High-Speed Expert, Lee Ritchey about power delivery systems (PDS) design. They discuss the definition of PDS and the elements involved in its design. Lee explains the challenges in PDS design, including the need to reduce power supply voltage and engineer high currents. They also address common myths and misconceptions about PDS and the importance of considering it early in the design process. Lee provides a concrete tip for improving PDS design and shares his thoughts on the future of PDS. The conversation concludes with recommendations for further learning on PDS design.

Episode Resources

Lee’s Power Delivery System Course

Speeding Edge (Lee Ritchey’s website)Β 

Sponsor Resources
  • πŸ“˜ Visit The EEcosystem Website For a Free Download to: Samtec’s white paper: Wideband
    launches: Much more than Footprints on PCBs. and receive a free 90-day subscription to all of
    Eric Bogatin’s training at The Signal Integrity Academy

    πŸ‘¨πŸ½β€πŸ’» For free Technical Resources and to Learn more about Keysight Pathwave EDA Software
    Solutions visit the homepage now.

    πŸ”— For all of your high-speed and RF connectors visit the Samtec website and access excellent
    engineering resources while you are there.

    ⛰️ Visit Summit Interconnect for all your complex PCB manufacturing needs.

    πŸ”— Visit Isola Group global for High performance laminates and prepreg materials for PCB
    manufacturing, as well as new IC packaging interposer

    πŸ’½ For high complexity EDA solutions visit SIEMENS EDA Website

    πŸ’‘ For a free subscription Signal Integrity Journal and articles about SI/PI/EMI, news and
    technical resources follow the link above.

    πŸ“¨ Subscribe to Analog io a grass-roots weekly Newsletter written by hardware engineers, for
    hardware engineers!

    πŸ“‘ For Custom RF and MW PCBs visit the Transline Technology Website to learn more. Visit

    πŸ”Œ Picotest specializes in high fidelity testing and measurement tools, primarily for power-relate
    applications. Visit their website for more product information and excellent training materials from
    expert Steve Sandler


								 Judy Warner (00:01.732)
Hi, Lee. So good to see you again. I'm excited to talk to you about power delivery systems today.

Lee Ritchey (00:08.848)
Well, it's my pleasure to be a part of this little adventure.

Judy Warner (00:14.128)
So I was made aware that you did this online class about power delivery systems recently through Endeavor Media. So I knew if you're teaching a class about it, it's something that our listeners would want to know about. So why don't you start out by defining what a power delivery system is and what elements are involved in that from a design engineering perspective?

Lee Ritchey (00:41.208)
All right, well, our delivery system's job is to make sure power is delivered to an integrated circuit inside a package so it can do whatever it's designed to do. Historically, we have considered the power delivery system be the DC converter, the power and ground layers on the board, and the capacitors that engineers place on the board. And...

That used to be enough as we have gone up the speed curve and the transistor count curve that has had to be expanded to include the capacitors that are put on the IC package by the manufacturer of the component and the capacitance that's engineered into the IC itself. None of the modern component.

we use will work unless all of those have been included. So, PDS design now includes all of those together. And for us engineers who are designing the boards, two of those we don't have any control over. One of those is of course the capacitors that the IC manufacturer put on the package. And the other is what's on the IC. I forgot one element and that's the package itself. Because...

Judy Warner (01:58.311)

Judy Warner (02:06.096)

Lee Ritchey (02:07.768)
We've got such high currents, the package itself has to be included in the design flow. And of course that is not in the hands of the board designer.

Judy Warner (02:20.064)
Right. So how do we, well, first of all, a question, a personal question, our listeners might know, but I may not know. I came from, you know, I have experience in the EDA space. And in that space, a lot of times they talk about the power delivery network or a PDN, you know, there's PDN software. What's the difference between a PDN and a PDS?

Lee Ritchey (02:46.344)
Well, as I've said a number of times, it's tomatoes, tomatoes. Some people for some reason want to use the word network. I consider that a bit misleading because mine says networks are a bunch of wires. And of course a PDN does not look like that. If it had a bunch of wires, it wouldn't work. So the industry, for example, if you go to DesignCon, you'll see PDS as the common.

Judy Warner (02:52.298)

Judy Warner (03:02.139)

Lee Ritchey (03:15.248)
designator power delivery system because that's in fact what we're engineering.

Judy Warner (03:19.881)
Okay. Well, that clears that up for me anyways. So you mentioned all these elements that are involved and then, you know, there's the chip level stuff and then there's the stuff that a board designer needs to own and consider why has it become so challenging and why did you decide to teach a whole course about this?

Lee Ritchey (03:44.68)
Well, it most of all has to do with the level of integration we have in integrated circuits, where it is not uncommon to have an integrated circuit with several hundred million transistors. And how that density is achieved is by making the devices so tiny that they can't tolerate a high power supply voltage.

So we get hit twice. We have to reduce the power supply rail voltage down and most of the time now it's under one volt. And at the same time, the currents that you have to engineer are in excess of a hundred amps.

And there was a paper done at DesignCon this last January where that current was over a thousand amps. And how do you get that much current?

into art.

Lee Ritchey (04:51.292)
with copper layers and print circuit board inflated through holes and packages that are, typically have, if you're lucky, metal layers that are one mil thick. And that's basically what's driving pretty much all of the tools. Most of the tool vendors now have

the ability to include all those elements in your model. And you kind of have to do that.

Judy Warner (05:23.184)

Judy Warner (05:27.148)
Now, here's a loaded question. Are the models accurate?

Lee Ritchey (05:33.604)
Depends, as Eric is wanting to say all the time.

Judy Warner (05:38.189)

Lee Ritchey (05:42.408)
When I teach my class, my mantra is an unvalidated simulation is worth the papers written on, meaning that you have to somehow verify that the models you included represent the real hardware. Because the tool itself does a good job. It's more often than not, it's incorrect models. Most of us have had to resort to building.

Judy Warner (06:04.837)

Lee Ritchey (06:10.6)
prototypes and measuring them in order to get that historically that's how we've all done it. There exists some tools that if you are good at driving them will give you a pretty decent model. The trouble is there are so few people who can drive those tools that I mean that's fundamentally a problem across the whole board including PDS design. There's so few people with the skill right now.

Judy Warner (06:13.249)

Judy Warner (06:32.011)

Lee Ritchey (06:40.956)
that we're hurting as an industry.

Judy Warner (06:45.156)
Which I, you know, which kind of speaks to my second point is why you decided to create this core so people could upskill. And yeah, at DesignCon, I don't know if you saw Steve Sandler's paper or his booth, but they were testing a 2000 amp core power rail. And he made, he had refrigerated probes.

Lee Ritchey (07:15.352)
Oh, I believe that. I believe that. Yes.

Judy Warner (07:15.524)

And he had water cooled last year at DesignCon, but this year it was refrigerated. And he said every semiconductor company has contacted him. So I guess we're pushing the power envelope for a variety of reasons. So this sort of ties into conversations I've had with him. So in regards to the board designer, what are some common myths or misconceptions?

specifically around the PDS that maybe you're trying to address in your class.

Lee Ritchey (07:54.408)
Well, certainly at the top of the list is application notes that almost never are correct.

I can't say I've ever seen one that is correct. And of course, engineers who are beginners, that's what they have to work with. And when I teach my class, we go through and illustrate the things that are required, the elements that are required, and then I go and look at a typical applications note. For example, this is historic, way back when.

Judy Warner (08:06.107)

Judy Warner (08:12.816)

Lee Ritchey (08:31.736)
a point one on a point on one microfarad capacitor where all you needed things were so slow. And I still see application notes being printed with that on it. And the frequencies that are involved in high speed switching are so far above where those capacitors are functional, they're just useless. And second is we...

We know that if we have a wide parallel bus, we need some plane capacitance in the pin circuit board to supply those frequencies. And today, to date, I have not seen an application note that suggests you should have plane capacitance built into the pin circuit board still. So if you're attempting sort of to...

illustrate how some of the smarter IC manufacturers have dealt with this is Intel has been doing this forever four layer board does not have a plane capacitor and so Intel has integrated onto the package and onto the die all the capacitors required for the part to do its job That's been going on for at least 30 years of course the engineers at Intel know that and they know that they're

Judy Warner (09:44.081)

Lee Ritchey (09:52.296)
customers are designing four layer boards and don't know much about this and so

Lee Ritchey (09:59.676)
They want their customers to succeed. And so that's what they've been doing. And lately companies like Xilinx and Altera and Broadcom are doing the same thing. And I won't name who it is, but I saw an app note from one of those that at the bottom said, we have engineered all the capacitors on the Dian on the package you require for this part to work other than.

Judy Warner (10:02.017)

Lee Ritchey (10:27.656)
the capacitors for the switching noise on your switching power supply. And the last statement, this was on page one, because engineers don't know how to design power delivery systems. You can kind of guess that they got some backlash on that and that last sentence is not on the current app note.

Judy Warner (10:40.348)
There it is in writing from IC manufacturers. So.

Judy Warner (10:53.403)
Somebody got in trouble for that one.

Lee Ritchey (10:55.637)
Well, let's offend our customers right off.

Judy Warner (10:59.453)
Yeah, we've done it for you because you're a dope.

Lee Ritchey (11:02.464)
Yeah, pretty much that's a translation. Unfortunately, they're correct. And that is happening quite a bit. And so for an awful lot of the parts, you don't have to be have very much skill.

Judy Warner (11:15.929)

Judy Warner (11:20.952)
Well, and I always like to say, and you and I have talked about this at different levels many times, I always say everybody's innocent because EE's are laying out boards and they were never taught it. You know, they're just thrown in the deep end of the ocean many times without all this insight, which is why I do this podcast in the first place, right? Is to help engineers navigate those gaps. So.

Lee Ritchey (11:43.251)

Judy Warner (11:49.068)
Anyways, I didn't want people to think we're saying they're dopes. They're not. So we're just here to help them. So I always like to, on the podcast, Lee, give our listener audience, like, one thing they could do today to make themselves better. Like, do you have one concrete tip? If someone listened today, I could go do this one thing to make my

Lee Ritchey (12:15.368)
Well, as long as we had wide parallel buses like AdRIS and data buses, if I could give you northern advice and say make sure you engineer a good interplane capacitor into your pin circuit board stack up.

Judy Warner (12:29.869)

Lee Ritchey (12:30.696)
Because there was a, of two or three hundred EMI problems I have trouble shot, only except one have been because that was not part of the board layout. And it's required for those high speed signals.

Judy Warner (12:47.2)
Well, back to Steve Sandler, and I've said this many times, is that what he's told me, you know, as a power expert is when he designed the power system for the International Space Station, like 200,000 pages had a stamp on them that says does not include board effects. And now he said, now forget it. It's all board effects. Like...

This is the difference of the times, right? Like you said, there's way more power now. And before it used to not matter, and now it matters a lot.

Lee Ritchey (13:14.312)
That's true. That's true, yeah.

Lee Ritchey (13:23.432)
So a little bit, I do this in a course to give perspective to people who have not done this before. It takes about 60 amps to start your car and you know how big the cable is that goes from the battery. It's about as big around at least as your finger. And we want to do 120 amps in little films of copper.

called Planes.

Lee Ritchey (13:58.408)
That's not simple. And I illustrate sometimes the last big design we did was a router with a switch fabric chip that was 120 amps at 0.9 volts. And the board had 29 different power supply rails on it. A couple of 128 gigabit links. I did all the SI engineering in about two days. It took a whole month.

Get the PBS right.

Judy Warner (14:29.806)

Judy Warner (14:33.116)
So at what point in the design, because it should design engineers be thinking about the PDS?

Lee Ritchey (14:44.592)
before you do the stack up of the print circuit board.

Judy Warner (14:47.668)
Okay, so that's the critical piece.

Lee Ritchey (14:51.329)
It has become more critical than all the single integrity work you have to do. It's harder by a lot.

Judy Warner (14:59.196)
That's wild. Why?

Lee Ritchey (15:02.408)
Why is that? Because the primary things that are in most designs now are memory, and almost every connection is a differential signal.

Judy Warner (15:08.719)

Judy Warner (15:13.369)

Lee Ritchey (15:14.868)
And differential signaling is, by comparison, to routing a parallel bus, a slam dunk. You route two wires, the same links, and you go have a beer. And you're all done with the differential pair.

Judy Warner (15:22.552)

Lee Ritchey (15:32.692)
And well, that has to do with choosing your board material, doesn't it? Not board material. Yeah.

Judy Warner (15:32.74)
unless you have skill.

Judy Warner (15:39.148)
Yeah. And then again, knowing, really getting to know your board materials is really important and not just blindly trusting those things as well. Yeah.

Lee Ritchey (15:50.876)
That's the other shoe, dropping the other shoe.

Lee Ritchey (16:00.336)
without question, the PDS design just dominates everything we do. And if you were looking at the papers at DesignCon, it was dominated by PDS design.

Judy Warner (16:06.804)
Okay. So you're.

Judy Warner (16:14.024)
interesting. So you're saying stack up is critical and knowing what's what with your circuit materials.

Lee Ritchey (16:28.308)
Yeah, well, the material used in the stack up doesn't have much effect on the PDF itself. The serral length is what that is affected. But the copper, how much you have and where it is, is critical.

Judy Warner (16:34.692)
Well, the pre-preg. Oh yeah.

Judy Warner (16:44.552)
Mm, mm, okay. Got it, okay, I misunderstood you there.

Lee Ritchey (16:49.604)
That's critical. Yeah. And that's, that's why PDS design has to occur before anything else. And the other element of the stack up is that plane capacitor we talked about. Has to be engineered into the stack up.

Judy Warner (17:06.528)
Okay. All right. These are some really good tips. Plus, I'm going to send folks over to take your class and if they're interested, they can go get the full treatment. So before I let you go, Lee, I was just thinking about our conversation about the immense power that you and I both saw being exhibited at DesignCon just a month ago. If it's so challenging now, what does the future hold?

Lee Ritchey (17:36.252)
Well, I'm thinking I might retire.

Judy Warner (17:39.493)
Ha ha!

Judy Warner (17:43.957)
You recorded your class. I'm out

Judy Warner (17:49.552)
Good luck.

Lee Ritchey (17:50.811)
Both my partner and I both decided that when they want us to do 128 gigabits per second, we are finished.

Judy Warner (18:01.092)
It's like you guys are thinking we got you this far you're on your own now.

Lee Ritchey (18:04.672)
Yes, yes. If you went to DesignCon, and we did this on purpose, we turned all the booths that were showing that sort of thing, none of the signals were in pin circuit boards. They were all in twinX.

Judy Warner (18:13.808)

Judy Warner (18:18.573)
Oh, okay.

Right, so it's all the flyovers and...

Lee Ritchey (18:24.12)
Yeah, yeah, they're... And so the question to be asked, and this is kind of the subject, to be asked is why, and that is at those rates, no matter how hard you work, you can't find glass weave that's good enough to keep the skew under control.

Judy Warner (18:25.933)
Cause yeah.

Judy Warner (18:43.276)
Right. Okay. So Samtech and Molex and everybody else is just going to do really well then for the future.

Lee Ritchey (18:50.476)
Oh yes, yeah, yeah. And the solution is laminate that does not have glass. And we are working with two developers on that right now.

Lee Ritchey (19:06.716)
We'll see.

Judy Warner (19:07.886)
When are we gonna get to hear about that, Lee Richie?

Lee Ritchey (19:11.752)
I had this, I signed an NDA. I had, I can't tell you.

Judy Warner (19:16.684)
I know you can't tell me but like when do you think any of that?

Lee Ritchey (19:20.714)
before this year is out.

Judy Warner (19:22.92)
Okay, well that's helpful. Yeah, I don't want you telling secrets now. I just wanted to know when we might expect. Okay, well, this is a perfect place to wrap up then.

Lee Ritchey (19:33.379)
We have test boards, how's that?

Judy Warner (19:35.772)
Okay. Well, I want you to call me the minute that that's available, widely available and you can teach our listeners and talk about that a bit. Okay. Good deal. Well, Lee, it's always a delight to talk to you. You always have so much to say on all the leading and bleeding edge stuff. I'll definitely send people to your class. Where else would you like me to send them to?

Lee Ritchey (19:47.5)

Judy Warner (20:05.156)
your website, your book, where else would you like folks who are listening to go?

Lee Ritchey (20:07.56)
Well, our website has, we have 5D online courses over all the subjects starting with fundamentals and getting you all right, title is signal integrity and getting to 56 gigabits per second. And what we are just talking about here is one element of that.

Judy Warner (20:15.778)

Judy Warner (20:28.065)

Lee Ritchey (20:35.92)
That is an online course and you can find out about it on our website.

Judy Warner (20:42.069)
Okay, great.

Lee Ritchey (20:45.232)
and I get to sit here and do it, which is kind of nice.

Judy Warner (20:49.096)
Yeah, right. The upside of remote work, right? You can just...

Lee Ritchey (20:53.556)
What people can't tell is I'm looking out at the Pacific Ocean right now.

Judy Warner (20:58.664)
Yeah. Rough life. It's rough. Somebody's got to do it, Lee. It might as well be you. You've earned it. You've ridden the ride through all these years. So enjoy. Well, Lee, thank you again for coming today and teaching us about that. And I will certainly put those links in the show notes. Thank you. For our listeners, make sure you go check that out. There's some really great

Lee Ritchey (21:01.373)
It's hard. Yeah.

Lee Ritchey (21:09.072)
Thank you.

Lee Ritchey (21:20.025)
Okay, thank you.

Judy Warner (21:28.46)
Enlightening Conversation with Lee Ritchie and we will see you next week. Until then, remember to always stay connected to the ecosystem.