Hi, everyone. My name is Ben Miller and this is Life in the Fast Lanes,
a new video series about everything high speed digital from Keysight Technologies.
In this series, we'll be talking about industry trends, new standards, transmitter and receiver testing,
anything to do with high speed digital development and designing.
In this first episode, I got to talk to Jit Lim, Keysight's resident USB expert, to talk about the new USB4 Version 2.0 standard.
Now, we all know about USB. We use it every single day. I'm using it right now in my webcam and my microphone.
It's everywhere in consumer electronics. But did you know about USB4 Version 2.0?
It's a brand new standard out of the USB-IF and it brings the data rate of USB up to 80 gigabits per second.
My conversation with Jit covers a wide range of things, from the details of the spec to the test challenges.
And we even talk a little bit about some of the new mandates coming out of EU and India about Type-C phone chargers.
So, without further ado, here's my conversation with Jit.
Before jumping into the USB4 Version 2.0 standard, why don't you tell us a little bit about the history of USB?
Yeah, it's been a while, but way back when they introduced universal serial bus, USB 1.0
and the idea was that it would become the unifying standard.
But back then there were other standards you may have heard of, standards like FireWire and other, say, competing technologies.
But over the years, USB has progressed. You may have heard then of USB 2.0.0, you may have heard of USB 3.0, 3.1, 3.2...
Essentially, these standards just got faster and faster.
So you may have heard of a Type-C connector and that came with USB4. It needs to run a Type-C connector. That's USB4, version one, if you will.
And the latest iteration is USB4 version 2.0, which runs on a Type-C.
I believe that today, USB has made its vision of being a universal serial connector.
There are just not that many competitors out there as far as the ubiquitous connector technology.
So what is the difference between the connector, USB Type-C, and the signaling standard, USB4?
So when I mentioned USB 1, USB 2, USB 3, USB4, those are the signaling, the speeds and signals that run over the USB connector and wire.
So it's what you test, if you will.
When folks use words like standard A, standard B, micro B, mini B, Type-C, that is the physical connector.
So signals like USB 2.0, for example, can be sent over a standard A connector, standard B, or a Type-C connector.
So that's how you differentiate between the signaling technology and the physical connector.
So USB has been the news lately because the EU and other countries have been considering or passing legislation to make USB-C the only cell phone charger connector.
Can you tell us a little bit about how this is going to affect the USB market?
The vision, I believe, is: instead of having all these different connectors, why don't we go to just one universal Type-C.
So with all these mandates, et cetera, you'll more quickly move towards one Type-C connector.
And I say more quickly because over time, it will happen.
The reason is that Type-C is just so much smaller, it's compact, and it's got way more capabilities than the standard A, B, micro B.
It's just a lot more capability than the previous alphabet soup, if you will.
Type-C brings USB-PD, which comes with a lot more capabilities that was not seen before.
So it's coming, and these mandates just push it along faster than it normally would have.
This past week I got a brand new i9, top-of-the-line latest iteration of a very strong PC, and it has three Type-C connectors.
It did not have any more standard A, so I believe the products out there are removing [ports other than] the Type-C.
Now, having said that, I still needed to use Ethernet, so I had an adapter, C to Ethernet adapter.
Let's see, I had a USB stick that was around, it was A. So I had to get a C to A.
So, there's no question we are moving quickly towards the C connector.
But remember, I can only type so fast, so there'll always be a USB 2.0 signal running over the Type-C, so I can use my USB 2.0 mouse.
Let's go ahead and jump into the new standard
Can you tell us everything that's changed between USB4 and USB4 Version 2.0?
In general, as we go from one speed standard to the next, we double the speed.
So the previous iteration was what we call USB4.
So it was also logoed as, or branded as, USB 40 gigabits per second,
which showed that we had two 20 Gb lanes equaling 40 in each direction.
So 40 gigabits in one direction, 40 gigabits in the other direction.
Now, for USB4 version 2.0, it's labeled 80 Gbps.
It's a doubling in this case. Now you have each lane running at 40 gigabits per second.
So two of those gives you the 80 gigabits in one direction and 80 gigabits in the other direction, hence USB 80 gigabits per second.
There is a third dimension to this: USB-PD or USB Power delivery.
There are different variants of this. The latest one is Enhanced Power Delivery, which runs up to 240 watts.
So this is 48 volts at five amps. This is optional.
USB4 Version 1 and 2 products need some basic form of power delivery,
but they don't necessarily have to run up at 240 watts or 100 watts.
It's an enhancement to the connector, but it's not a requirement to the connector.
So something I found interesting about USB4 Version 2.0 is that it uses PAM3 signaling for the first time.
I know that ethernet and PCIe have adopted PAM4 signaling in order to increase the bitrate.
Could you tell us a little bit more about why the USB-IF chose PAM3?
I always use my mom as an example. So, my mom is always going to buy a $2 USB4 version 2.0 cable.
Cables like these are very low cost and very lossy and very noisy to be able to satisfy that market.
The signaling at PAM3 is going to go through a lot of loss and be noisy.
If you think about it, NRZ zero to one has this level.
If you slice that with PAM4, each of those little segments are much smaller and noisier.
PAM3 is a compromise between noise and bandwidth.
The other thing to know is the other technologies that you may have heard that do PAM4, they use very high quality,
much more expensive, say, PCBs or connector types.
USB will always be a technology for my mom because it's in the, shall we say, the lower cost consumer market.
So I've heard that the USB-IF has been working on rebranding some of the USB terms to better be understood by less tech savvy customers.
Can you tell us a little bit more about their efforts to rebrand and what that looks like?
The second most important question that comes up is this branding. It depends on the audience.
So when USB4 version 1.0 was introduced, inside the USB4 specification document,
Gen 2 was running at 10 Gbps, and Gen 3 was running at 20 Gbps.
For audiences like us and our customers, that USB 40 Gb number, to be honest, really means nothing.
It's more of a, shall we say, a marketing term, because it's about two 20 Gbps rates combined into one.
That document was revised. So they just called it, the name of the document is USB4 version 2.0.
And they added a new rate: Gen 4 at 25.6 gigabaud PAM3. But in our world, that number 80 really doesn't mean a whole lot.
For us to test, we never actually test at 80 gigabits per second. We test the PHY layer at 25.6 gigabaud PAM3.
So the reason for what may appear to be some confusing terminology has to do with who the audience is.
What are the biggest challenges that USB developers are going to have with the latest spec?
The biggest challenge we'll have, by far, is not the speed in this case, because the speed actually did not go up that much.
The biggest challenge by far is the signaling level. The reason...
You remember I mentioned how PAM4 has so many levels, It was a challenge?
PAM3 is also very challenging. We essentially lost a third of... Half the margin, if you will, going to PAM3.
And so the number one challenge by far is trying to analyze and characterize these small signals
because of the speed, and they're multilevel. So there's less way to, say,
differentiate between the different levels because everything's compressed and there are more levels.
Do you think that there is a physical limit for how fast we could send bits down a channel?
And if so, what does that mean for future generations of USB?
You know, 20 to 30 years ago, if you asked me the question, I made a comment along the lines of,
"oh, yeah, when signals get to five gigabits, everything's going to be optical."
I said that the circuit board is going to have optical signals on circuit boards. The case will be optical.
Everything is going to be optical. This was 20, 30 years ago.
Well, what I didn't realize is the innovation and the great brains that are involved in the world of silicon design.
It's amazing, right? They're pushing 25.6 gigabaud. They're pushing at a PHY layer 40 gigabits over low cost,
my mom's low cost cable, my mom's low cost PC.
So who knows what this wonderful geniuses in the silicon world are capable of doing?
We are always working with all our leading smart silicon vendors, IP vendors,
to look at the next generation beyond USB4 version 2.0, that just never stops.
I hope you enjoyed my conversation with Jit. We had a blast talking. We talked for far longer than you saw in the video.
You can see our full conversation in the Keysight Talks Standards: USB4 Version 2.0 webinar that will be out pretty soon after this video comes out.
So to [get] more information about the webinar, or to find out more about Keysight's USB solutions, check out the description for the link,
or go to www.keysight.com/find/usb
There's so much to get excited about with USB Type-C, with its faster data rates and its power delivery capabilities.
There's also a lot more going on with a lot of different high speed digital standards.
So be on the lookout for new episodes coming soon about those, and I'll see you next time on Life in the Fast Lanes.