Power Corner: ESD Protection for 48-V Automotive and the 58-V Short-to-Battery Challenge
Description
The proliferation of 48-V automotive
In this week’s Power Corner, Andreas Hardock, Principal Product Application Engineer at Nexperia, discusses the changing ESD design requirements around newer 48-V automotive subsystems intended to supplement or replace conventional 12-V networks.
First, Hardock describes the logic behind shifting to 48 V. Quadrupling the voltage could allow 4x more power to flow through the system (P=IV) or cut the current by ¼ for the same power, reducing wiring loss to 1/16 (Ploss=I2R). “I think the main driving point here is efficiency, and the second one is efficiency, and the third one is efficiency,” says Hardock. Lower current also allows thinner, lighter cabling, and keeping the net < 60 V keeps it within the low-voltage safety class.
Regarding the permanence of 12-V automotive systems, Hardock explains that it isn’t going away soon, with most vehicles deploying hybrid architectures that step 48 V down to 12 V for PCB interfaces. He also notes that while some vehicles, like Tesla’s Cybertruck, are close to using only 48 V, these are rarer. “It’s not going to happen. It will take years or even decades,” says Hardock.
Short-to-battery challenges
Hardock presents the fundamental issue: ESD robustness requirements in kV, e.g., 8 kV, 15 kV, or 25 kV, stay the same as for 12-V and 24-V systems. The new challenge then becomes the short-to-battery event.
“Once the isolation is damaged or so, there is a risk that the cables are shorted to the battery voltage,” says Hardock. Once a damaged connector or cable shorts an interface pin to the battery supply, that pin sits at battery voltage for as long as the fault persists, and the ESD protection device at the connector must stay off rather than try to absorb current the battery can supply without limit.
The components must withstand the full battery voltage. For 48 V systems, the short-to-battery test requires them to survive 58 V (Figure 1). Hardock continues: “And this is the challenge for the ESD device, too..We place the ESD device at the connector…the ESD device will see the 58 V.”
ESD devices are built for pulses lasting hundreds of nanoseconds, not continuous battery current. “No devices on the market will survive this,” says Hardock. “The battery voltage and the current coming out of the battery are unlimited…it can be 10 A, 20 A, 30 A, 60 A, whatever.”
On the potential for series current-limiting devices, Hardock says this can be acceptable on low-speed buses with data rates of a few megabits per second (Mbps), e.g., LIN, CAN, or lower-speed automotive Ethernet, but high-speed interfaces generally cannot tolerate series elements. “This highly impacts signal integrity,” says Hardock.
ESD matching: trigger, holding, and clamping voltage
From a design perspective, the engineer must match the characteristics of the external ESD protection with the on-chip ESD protection integrated within the automotive transceiver (refer to Figure 2). Matching is especially critical when no common-mode choke or ferrite bead sits between the two.
Hardock explains that most modern ESD protection devices are no longer simple Zener stacks. He estimates that about 90% use topologies such as SCRs or open-base transistors, which show a “snapback” effect.
The first parameter Hardock highlights is the standoff voltage (VRWM): the highest voltage a protection device can sit at continuously while staying off. Because the ESD device sits at the connector, it sees the full test voltage during a short-to-battery. “Then they need to have a standoff voltage which is beyond 58 V…Because the device is placed at the connector, and during the short-to-battery, it sees the entire short-to-battery testing voltage, which is 58 V,” says Hardock.
Each device has a trigger voltage (Vt). Below it, the device stays highly resistive and conducts essentially no current. Once the trigger voltage is reached, the device turns on and snaps back to a lower holding voltage (Vh), the level at which it stays on and keeps conducting.
While it conducts ESD current, the line voltage settles at the clamping voltage. That voltage isn’t fixed: it rises with pulse current according to the device’s dynamic resistance, so a strong ESD pulse of 10 or 20 A clamps higher than a weak one of a few amps. Engineers read all three parameters from the device’s I–V curve, which Nexperia measures with its transmission line pulse (TLP) setup, a repeatable alternative to ESD gun testing, which Hardock notes can carry tolerances of up to 30%.
In other words, the engineer must ensure two things:
- The external ESD device’s standoff and holding voltages sit above 58 V, so it stays off during a short-to-battery. If a transient triggers it during the fault, a holding voltage below 58 V would let the battery keep it latched on, destroying the device.
- The external ESD device’s clamping voltage stays below the transceiver’s internal Vt across the ESD current range. Otherwise, the internal protection turns on and, if it has deep snapback, pulls most of the current into the chip.
The transceiver’s own protection must meet the same 58-V level. “During the short-to-battery, the IC pin sees the same voltage, and that’s why their internal ESD structure also has to trigger beyond 58 V,” says Hardock. That requirement is pushing chip vendors to redesign. “This 58 V is not easy to survive at the IC level in terms of short-to-battery, and they also need to adapt their internal IC ESD protection. And this is happening right now at the semiconductor vendors.”
The interface landscape and how that impacts ESD
However, it is also critical to note that each automotive interface, whether it’s LIN, CAN, or automotive Ethernet, will use different passives. Hardock starts off by describing the ESD protection used for the LIN interface: “LIN usually has a shunt capacitor…and sometimes a ferrite bead.” He continues, “If we look at CAN, some car OEMs out there require a common mode choke (CMC).” He notes that automotive Ethernet also uses a CMC, at least up to 1000BASE-T1.
Naturally, different ESD devices will change the design requirements for ESD robustness. According to Hardock, a CMC decouples the two protection devices (external + on-chip), so the internal structure’s characteristics matter much less. “Then you don’t need to care how robust the on-chip ESD protection is, or what its turn-on voltage is, if you have a common mode choke, right? You don’t care at all,” says Hardock.
Without a CMC, the current takes the lowest-impedance path, so the external device must trigger first. “If the on-chip ESD turns on first, at lower voltages, then the pulse will go through the IC, which we don’t want, obviously…So, it [external ESD] triggers first, reacts first, and then takes the entire ESD power and clamps it to ground,” states Hardock.
Automotive Ethernet has one added advantage: series AC coupling capacitors, which LIN and CAN lack. “The AC capacitors, which are in series, will block the DC voltage, which is good for the IC. But for the ESD device, we have the same challenge left, I would say,” says Hardock.
Whether a design needs external ESD protection at all depends on the OEM’s requirement, which Hardock says ranges from 6 kV to 25 kV, compared with the IC’s own rating. “If your system requirements are higher than the absolute rating of your IC, then you definitely need an external one. Otherwise, you will damage your IC during the ESD.”
Transcript
AS: Welcome, everyone, to Power Corner. I’m your host, Aalyia Shaukat, Editor-in-Chief of Power Electronics News. Today, we’re sitting with Andreas Hardock, Principal Product Application Engineer at Nexperia. Thank you for sitting with me today, Andreas. It’s very good to have you.
AH: Thanks for being with you. Thanks.
AS: Well, okay, so the topic today is ESD protection for 48-V systems in automotive. So maybe we could just talk more generally first. Maybe you could talk about the motivation for adding 48-V nets alongside the existing 12-V nets in automotive designs. What systems is this shift impacting in particular?
AH: That’s a good start. So we do have 12-V systems since forever, and we also have 24-V systems, right? So there’s something in between already, the 24 V.
And I think the main driving point here is efficiency, and the second one is efficiency, and the third one is efficiency. So it’s more about efficiency, because you can put 4x more power through your system if you just shift the voltage by 4x, right? Compared to the 12-V system. You reduce losses and increase the power. I think this is it. This is the main driver of this.
AS: So, pretty simple answer there. Are there cases where OEMs are pushing more of the vehicle onto that 48 V for the low-voltage systems?
AH: Can you explain a little more?
AS: So I know that you have the 48-V net alongside the existing 12-V, but are there cases where it’s just a 48-V net?
AH: Yes, maybe, yes. I mean, mostly it’s hybrid systems, right? You have 12-V systems on a lot of PCBs, but you have 48 V in general, so you have a step down from 48 V to 12 V, and then even more. Because when we talk to car OEMs, in most cases they still use 12 V on the PCB, right? For interfaces and everything.
So the 12 V is not completely removed. But there are also some cases, like the Cybertruck, where there is more or less 48 V only. So there’s a new mindset change, probably, and people are going more and more to 48 V and removing the 12 V step by step.
It will take time. It won’t happen overnight. It’s not going to happen. It will take years or even decades or something. But step by step, since efficiency drives this, it will happen.
AS: That makes sense. Okay, well, thank you. That’s very helpful to know. But shifting into ESD, how does this shift affect electrostatic discharge, or ESD, robustness?
AH: People ask us this a lot, because the whole topic of 48 V is kind of new to everyone. And this is very simple to answer, because there are two challenges if you think from the ESD perspective.
The first [challenge] is the ESD robustness itself. It hasn’t changed at all, so this is not an increase in ESD robustness. In terms of kV, we have the same requirements for 12-V or 24-V systems, so there’s no change at all.
But a second challenge comes up: short-to-battery, or short-to-VBUS. Automotive testing requires all pins going outside the PCB to be tested for short-to-battery. And here, the thing is that the short-to-battery voltage in 48-V systems, the testing voltage, is 58 V. So it’s not 48 V; it’s 58 V.
At least this is the status right now. It may change because the specifications aren’t finalized yet; as of October ’26, it will probably be finalized in the next month or next year or so. But the latest info we have is 58 V. This is what every pin in a 48-V system needs to be tested against in the short-to-battery test.
AS: 58 V. Gotcha. So let’s talk about what the short-to-battery condition is. What causes this, and how often does it really happen in vehicles?
AH: It doesn’t happen very often, but when it happens, it’s a real stress for the system, right?
I think the use case in the field is when the connector or cable is damaged, and this happens during service or normal operation. Once the isolation is damaged, there is a risk that the cables are shorted to the battery voltage, right?
For interfaces, that means the interface pin is connected to the battery voltage. And as we said a few minutes ago, in a 48-V system, it’s 58 V. So it’s kind of a high voltage. It’s 3x more than in a 12-V system. In a 12-V system, we have 16 V, and in a 24-V system, we have 32 V.
So, a lot of numbers! But 58 V is a very strong requirement. It means a lot to silicon, right? All the electronic components on the interface need to survive this 58 V, and this is the challenge for the ESD device, too.
Because once we place the ESD device at the connector and there is a short-to-battery happening, the ESD device will see the 58 V. And it needs to survive. When it’s triggered by 58 V and then turned on, and it starts to conduct the power coming from the battery, it will not survive. Not only Nexperia devices—no devices out there on the market will survive this.
Some people are confused because we have also been asked why it can’t just conduct battery power to ground and then everything is great. But no, it cannot, because the battery voltage and the current coming out of the battery are unlimited, right? It can be 10 A, 20 A, 30 A, 60 A, whatever.
ESD devices are made for short pulses, 100 nanoseconds long, or pulses in the range of several hundred nanoseconds, and not for DC high voltage and high current. They will not survive this.
AS: That makes sense. So you have the external ESD device, and you also have the internal ESD on the transceiver, right? And it has to stay inactive during these short-to-battery events. I was wondering, and this could be a silly question, but couldn’t current-limiting elements be added in front, in series on the bus line, to prevent this kind of event?
AH: Yes, in theory, yes. That’s a very good idea, and we probably need to suggest this idea to some people out there.
But usually it only works in theory. I mean, you already have series components in some interfaces, ferrite beads or common-mode chokes. But doesn’t happen very often, right?
For low-speed interfaces—LIN, CAN, or automotive Ethernet with data rates of a few megabits per second—you can add something, and it’s okay. But for high-speed interfaces, you usually don’t add any series elements, because this significantly impacts signal integrity. Any kind of series element is impacting signal integrity, and this is critical, because if you put your signal through the interface and it’s not functioning…
AS: And these are often safety-critical systems now.
AH: Right. Right. But in general, this is a very good idea. Any kind of current limitation, if you can use it there—even if it’s only a 2- or 3-Ω resistor—it will help you for sure.
AS: Okay, that makes sense. Thank you. I was hoping you could walk me through the LIN, CAN, and automotive Ethernet interfaces in a 48-V system. Can you talk about that a little bit more?
AH: Yes. People in automotive know there are tons of different interfaces, but as you said, LIN, CAN, and automotive Ethernet—and I agree with you 100%—are the most common and most popular in automotive.
Automotive Ethernet came into the automotive picture about 6-8 years ago, and it became very popular during that time. It’s a departure from the usual commercial Ethernet, but in the automotive world, it runs on only one differential pair. The usual LAN, or commercial Ethernet, uses 4 differential pairs. In automotive, only 1 differential pair, right?
So there’s a big change in the harness, in the environment, and a lot of EMC changes came along with this introduction of using only one differential pair. But it’s getting very popular, as I said, and it’s the backbone of the new car architectures, right? It’s used a lot.
We talk to people about automotive Ethernet very, very often, and a lot of people say that LIN and CAN are legacy and will be removed at some point. But it’s not happening. In the real world, it’s not happening. Even if automotive Ethernet is a very powerful interface and very flexible, LIN and CAN have been out there for decades, and my feeling is they will still remain, because the whole environment, the infrastructure, all the components that are used for LIN and CAN are available, are cheap, and are very easy to install and use on the PCB, right?
CAN is also a single differential pair, similar to automotive Ethernet. Also, the harness is the same; we have an unshielded twisted pair there. LIN is even simpler. We have only one single-ended wire, 20 kilobits per second. Very slow, the slowest we have in automotive.
But as I said, it’s still easy to use, and for all these systems where you don’t have a lot of communication running, like braking systems, you don’t need high data rates. You can just use LIN, and it’s good. It’s functioning, it’s working, and people are happy.
AS: Gotcha. Well, let’s talk about that, because you’re saying all these interfaces are used, right? It doesn’t matter how old or how slow; the simplicity does matter.
So I understand, and I read your article, there are different passives, and they vary for each approach. There was the shunt capacitor and ferrite bead for LIN, or common-mode chokes on CAN and Ethernet transceivers.
So how does that affect how you match the external ESD device to the transceiver’s internal ESD protection?
AH: A very, very good and very important point here. LIN usually has a shunt capacitor on the schematic, ESD protection, and sometimes a ferrite bead. Not very often, but sometimes.
If we look at CAN, some car OEMs require a common-mode choke. They also require a termination network, which doesn’t affect ESD or short-to-battery at all.
And if you look at automotive Ethernet, we also have a common-mode choke there, at least up to 1 Gbps. Automotive Ethernet has several speeds: 10BASE-T1S, 100BASE-T1, 1000BASE-T1, and multi-gigabit. But up to 1000BASE-T1, people are using a common-mode choke.
This is an important point because any common-mode choke is an inductor. An inductor placed between the chip and its internal ESD protection and the external ESD protection we provide from Nexperia helps a lot for ESD because it separates the internal ESD from the off-chip ESD. Then you don’t need to care how robust the on-chip ESD protection is, or what its turn-on voltage is, if you have a common mode choke, right? You don’t care at all.
If you don’t have anything—no common mode choke, no ferrite bead, as we have for LIN, or sometimes also for CAN—you need to care. Because then, if the ESD pulse is coming into the interface, it sees two ESD protection devices: the external one and the one which is in the IC. The pulse will go the lowest-impedance path.
If the on-chip ESD turns on first, at lower voltages, then the pulse will go through the IC, which we don’t want, obviously. We want it to go through the external ESD device, and then we need to have the external ESD device trigger at lower voltages.
So, trigger first, react first, and then take the entire ESD power and clamp it to ground. This is how it should work. And when you have a common-mode choke, it makes this a lot easier and gives you a little more ESD robustness.
If you don’t have a common-mode choke, you need a little more effort, but this is nothing new for us. We have a lot of experience with this, and we support people in getting the right ESD protection on their PCBs.
AS: Well, actually, that does, because I read in your article that some designs will omit external ESD protection entirely. Why is that the case? Could these systems potentially have the common-mode choke, and that’s maybe why? Is that something you’d really recommend at 48 V, or is it really dependent?
AH: You mean using an external ESD device or not using an external device?
AS: Exactly.
AH: There’s no, let’s say, one answer to this, because it depends on the requirements the Tier 1s get from the car OEMs. Sometimes, if the IC itself is really weak in terms of ESD, then it will not pass any kind of system-level ESD tests, right?
Sometimes car OEMs require 6 kV. In other applications, they require 15 kV. We also know of some applications where car OEMs require 25 kV. So the requirements vary widely.
If your IC is strong enough to pass system-level ESD without an external device, you can pass, and you don’t need to add anything to your PCB. But if your system requirements are higher than the absolute rating of your IC, then you definitely need an external one. Otherwise, you will damage your IC during ESD.
AS: Thank you. That’s helpful to know. I’m going to switch a little bit here, but can you talk about the transmission line pulse, or TLP, measurement method? And just an extra question there: what are trigger voltage, clamping voltage, and holding voltage, and what is the relevance of each of these specifications?
AH: Usually only ESD people know what transmission line pulse is, but there’s really no black magic behind it.
It was developed several years ago because, if you do ESD testing with the ESD gun itself, the norm for designing and testing an ESD gun allows a lot of tolerance, right? Up to 30%. This is one thing.
The second thing is that if you do an ESD test, the result can be affected by how you hold the ESD gun, the angle to your PCB, all the electromagnetic fields, and how they impact your PCB and your final result. So there are a lot of tolerances happening around the ESD gun testing itself.
And so for characterization, for analysis, for much deeper understanding, people wanted to have something that is repeatable, which is reproducible, and this is TLP, transmission line pulse.
It’s a high-voltage source and two transmission lines with a switch in between. You load one transmission line, and with the switch, you can discharge it to the other transmission line. Both are 50 Ω, so you have a 50-Ω environment, which is great. It reduces your reflections a lot, and you have very consistent pulses, which you can create with this system. This is very helpful.
We use TLP a lot for internal characterization of ESD devices, and we also use transmission line pulses to analyze ICs, for example. If people ask, “What is the best ESD selection for the IC I use in my system?” we just say, “Okay, we can analyze this using our transmission line pulse method. Give me your IC. We will do the measurement in our lab, and in a couple of days you will get results.
And based on these transmission line pulse results, we can give you the best suggestion, the best recommendation.” What you do is create rectangular voltage and current pulses. You shoot them at your device under test, either an ESD device or the IC, as we said, and you can measure the reaction of your device under test to those pulses.
You can do several—tens, hundreds of pulses—increasing the voltage and current, and get a lot of information out of this. This is very, very helpful for us in terms of ESD.
AS: So can we talk about those specifications for the ESD device—the trigger voltage, clamping voltage, and holding voltage—and the relevance of those as well?
AH: Yeah. People know ESD protection as Zener devices in most cases, right? Because this is what they learned in school.
But of the modern, new ESD protection devices, well, 90% of them are not Zener stacks at all, right? In a Zener stack, if you increase the voltage across it, nothing happens up to a certain voltage, which is the breakdown voltage, right? And if you reach the breakdown voltage, the device triggers, turns on, and conducts the current, sending the pulse to ground. In simple terms, this is how a Zener ESD device works. And 30-40 years ago, when ESD protection devices were introduced, the Zener stack was used as the first ESD device.
Right now, there are a lot more topologies—SCRs, open-base transistors—and most of them have this snapback effect. So they turn on at a certain trigger voltage. We call this Vt, the trigger voltage. Below the trigger voltage, basically nothing is happening, so the ESD device is very high-ohmic and not conducting current.
Once the trigger voltage is reached, the device triggers and turns on, then snaps back to a lower voltage. Lower than the trigger voltage. And this is usually called the holding voltage. ESD people out there usually use the same word.
And then from then on, it conducts the current, right? Once it’s triggered, it conducts the current, and we have a clamping voltage, which is basically a certain voltage on the I-V curve, right?
So the clamping voltage isn’t a single value. It also depends on the clamping current, or IPPM, as the datasheet calls it. Clamping voltage usually increases with clamping current.
You might have different ESD pulses coming into your system. If one is very weak—you have only a few amps coming out of your ESD gun—then the clamping voltage will usually also be lower. If you have a very strong ESD pulse, with 10-20 A or so, then the clamping voltage usually also increases a little with the current.
This is all related: the IPPM, the clamping current, and the clamping voltage (Vt) are related through the dynamic resistance, Rdyn. So this is also a very, very important parameter.
AS: Right. So this needs to be factored in. So I mean, all of these…
AH: One sentence maybe we can add, because then we have the relation to the transmission line pulse: all this data—the clamping voltage, trigger voltage, and holding voltage—is what we get from the I-V curve, which we measured using our transmission line pulse setup. So we have a connection to your previous question.
AS: Right. It comes full circle. So you have these parameters. The ESD diode’s job is to handle the fast, high-voltage pulses while avoiding conduction during slow, high-energy DC faults, right? Like the short-to-battery.
So how should engineers weigh all of this when selecting that external ESD device, and when choosing the transceiver itself?
AH: So, I mean, the short-to-battery is very important, as we said, especially for a 48-V system. If people look at LIN, CAN, or Ethernet—on all three interfaces. For Ethernet, we need to narrow it down to 10BASE-T1S, 100BASE-T1, and 1000BASE-T1, because there’s a slightly different situation for multi-gigabit Ethernet.
But if we have, let’s say, LIN, CAN, and 10-, 100-, and 1000-BASE-T1, then they need to have a standoff voltage that is beyond 58 V, right? Because the ESD device is placed at the connector, during the short-to-battery test it sees the full short-to-battery voltage, which is 58 V. So, as we said previously, this ESD device should not be triggered by 58 V. Otherwise, as we said, it will just be destroyed or damaged, and you cannot use it anymore.
So the standoff voltage should be 58 V and above, and the holding voltage should also be above 58 V, right? Just in case, during the short-to-battery testing, your device is triggered somehow because of some additional effect there. And if your holding voltage is below the short-to-battery testing voltage, it will be caught in latch-up and damaged.
So the holding voltage and standoff voltage should be above 58 V, and this is the most important parameter people need to consider for their designs.
AS: So it seems to leave a fairly narrow window between 58 V and that internal trigger voltage. Could you give an example of how an engineer would match the two and, as you mentioned, how the external device’s dynamic resistance factors in? How are you going to weigh all of this and select the right components?
AH: Right. So as long as they have the standoff voltage and holding voltage above 58 V, they’re good to use an ESD device that won’t be damaged in this short-to-battery testing. But then again, they need to protect the IC that is behind it, right?
And now it gets a little tricky. We need to know the internal IC ESD characteristics, as we talked about a couple of minutes ago. We usually use a transmission-line pulse to get this information: what is the turn-on voltage of the IC’s internal ESD protection, right?
And there’s also something to do for the IC makers, let’s say, because they also need to survive this short-to-battery requirement, right? During the short-to-battery, the IC pin sees the same voltage, so its internal ESD structure also has to trigger above 58 V.
But as soon as we have the I-V characteristics of our ESD protection device and the I-V characteristics of the ICs, which we again get from the transmission line pulse measurement, we can do this ESD matching. We have done this many times over the last few years, not only for 48-V systems, but in general. And based on this information, we can pretty quickly say, “Okay, this ESD protection will be good for your IC, or not.” We have a lot of experience in this already.
AS: Gotcha. So correct me if I’m completely wrong here. The external ESD device’s trigger and clamping voltages have to sit above 58 V, so it stays completely off during short-to-battery. The external ESD device’s clamping voltage also stays below the transceiver’s internal ESD trigger voltage across the current range. Otherwise, the internal protection turns on and has that snapback, which you don’t want.
AH: Correct. This is correct.
AS: Okay. And that’s the matching that needs to be done for…
AH: Yes, this is the matching we usually do, right? And as I said, we’ve done it for 12-V systems a lot, but in these 48-V systems, it gets challenging. Especially for IC makers, because 58 V is hard for ICs to survive at the IC level for short-to-battery, and they also need to adapt their internal IC ESD protection.
And this is happening right now at the semiconductor vendors. But maybe we can also add to one question you had before, including these additional components—common-mode chokes and ferrite beads—and also AC coupling, right?
Because we have AC capacitors in automotive Ethernet interfaces. We don’t have them in LIN or CAN, but in automotive Ethernet we do. And they reduce the risk of short-to-battery damage to the ICs. Not for the ESD device, but for the IC pins, because the IC pins are sitting behind the AC capacitors. The short-to-battery is a DC voltage (58 V DC) applied for roughly 1 minute during the test. The AC capacitors, which are in series, will block the DC voltage, which is good for the IC. But for the ESD device, we have the same challenge left, I would say.
AS: That’s very helpful to know. Thank you for explaining that. And there’s a lot of variety between LIN, CAN, and automotive Ethernet, all of the passives, the options for ESD…
AH: Welcome to the automotive world.
AS: Well, I appreciate you explaining all this to me. My last question: what kind of simulation can an engineer use to assist with ESD design for these 48-V systems, or these hybrid systems?
AH: We generally have three simulation methodologies, let’s say, for ESD protection devices. One or two of them are for ESD simulations; one is for signal integrity simulations. For ESD simulation, people can use the SPICE models that we provide. Those SPICE models are very simple models. They use, more or less, the diode characteristics and reverse polarity; we just adjust the dynamic resistance, breakdown voltage, clamping voltage, and so on.
They have limitations, right? They’re not dynamic, you know; they’re kind of static models. So there’s some kind of limitation to using them.
And there’s another one which is very promising, but a lot more complicated: SEED modeling, System Efficient ESD Design. This is based on the transmission line pulse data. So again, we have a circle here. Transmission line pulse is very important for us and for understanding ESD.
We use the data we get from transmission line pulse testing to build models from it. We have a colleague who is working on this. He is creating the full dynamic models, so there’s not only a static component, but also a time-dependent component in there. Because the transmission line pulse has pulses over time, it includes time-dependent information.
And we put all this information into SEED models, and with the SEED models, we can much more accurately predict the ESD robustness of your system. We can build SEED models for external ESD devices, for sure, for our ESD devices.
But again, having the I-V or TLP information from the IC itself, or also for common-mode chokes if you use one in your design—for all three, the external ESD, the common-mode choke, and the IC itself—we can create SEED models. Put everything in a simulator, in ADS or LTspice, for example, and then do ESD simulation.
And they are much more accurate compared to, let’s say, a very simple SPICE simulation. But we need to add this, too: it requires a little more effort. You don’t get…
AS: You have to do the TLP testing, and get the…
AH: And to adapt the simulation setup, it’s not as easy as a very simple SPICE model. So nothing comes for free here, yeah? If you need more accuracy, you need to put a lot more effort into it. Very, very simple formula.
AS: Well, thank you so much for your time, Andreas. This was very, very helpful. I know I learned a lot. Did you have any last thoughts that you wanted to add? Anything that I might have missed?
AH: Oh, no. I think the topics you covered today were very, very nice. We’re always happy to talk about this with anyone.
Also, the people out there who do real designs: if we can help them somehow to simplify their work—to do the analysis, to do the transmission line pulse testing in our lab, to do simulations, to just look at their design and help them somehow, and/or select a dedicated ESD device when they need one. Or, also, I’m very happy to just talk about such topics.
AS: Well, you’re very knowledgeable.
AH: Very nice. Thanks for inviting us.
AS: Thank you so much.
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