Applications team, and he is going to do a presentation here to explain replacing optocouplers with digital isolators. If you have any questions, you can write them through the chat here, and we'll cover them all at the end. Thanks.

Thanks, Tony. Good morning, everybody. This is Koteshwar. The topic for today is improving your system performance by replacing optocouplers with digital isolators. OK, let's get started. This is how the agenda looks like for today. We're going to start with-- in comparing the silicon dioxide based digital isolators against the optocoupler technology.

Then we'll will look at the lifetime comparison of the two technologies, followed by electrical comparison of the two device families with respect to various performance parameters, like switching performance, CMTI, input types, aging and reliability. And then, lastly, we will look at the typical use cases, how these isolators are used in some of the applications and how do they compare to optocouplers on these use cases. Like Tony mentioned, if you have any questions, please do write down in the chat, and we will cover them as we get the questions.

So the TI capacitive silicon dioxide based isolation technology. TI's reinforced isolators use, basically, input and output buffers. An isolator is nothing but a buffer which primarily transfers the input data to the output, but the input and output circuit is separated by a double capacitor silicon dioxide based insulation barrier, like you see in the diagram over here. So, hence, the input circuit and output circuit are insulated through the capacitive barrier.

These devices are manufactured and thoroughly tested in a controlled environment, and ensure a very high quality of the isolation lifetime. Silicon dioxide also offers one of the highest dielectric strength in the industry among the key dielectric components that are used in semiconductors for insulation. Like you see in the table here, silicon dioxide dielectric strength is about 500 volts RMS per micrometer, and all other key insulating components of the dielectrics have much lower dielectric strength. Unlike polymide and polymer, silicone dioxide insulators do not degrade with exposure to ambient moisture.

Here is a construction of the die level. Inside the device, this is how the die is placed on the lead frames and connected to each other through the bond wires. TI reinforced isolators have two isolation capacitors in series, and each capacitor is in each die. That's about TI isolator construction. Let's look at how does an optocoupler looks like in comparison.

The diagram that you see is a cross-sectional view of an optocoupler. And optocouplers use an LED to transmit signals across the isolation barrier, and the isolation barrier often can just be an air gap. The dielectric strength of the air and the epoxy material that is used for optocouplers, they're one of the lowest, as you can see in the table highlighted here, due to which it's not easy to achieve high isolation specifications for optocouplers. And the optocoupler dielectrics are also built in an assembly house, not in a controlled environment, like a silicon dioxide based isolators are built.

So next topic is the isolation lifetime. What is isolation lifetime? TDDB, Time-Dependent Dialectic Breakdown, is one of the key isolation lifetime tests that is used and conducted on isolators to determine the lifetime of isolators. This is of the standard methodologies that are used in the industry to determine lifetime of a dielectric or an insulation material.

The TDDB data is basically a plot where, on the x-axis, you have the stress voltage, and the y-axis has the lifetime or the duration for which the device can withstand. So the devices are tested for various stress voltages to determine how long they can withstand those stress voltages. And the amount of time that it can withstand is plotted in this curve, and is extrapolated to lower values to really determine how does it look like when you stress these devices or use them at lower voltages. That's how the lifetime of isolation devices is determined.

This is also the data that is required by some of the isolation-- component-level isolation standards for certification. VDE 0884-11 is one of such standards. And TI devices do have such data generated, and also have certification for the VDE. That's about the test, TDDB test. Now let's look at how do TI and optocouplers compare on this data.

I've mentioned earlier, on the x-axis, you have the stress shortage, which is a working voltage of the device. If you have an application, let's say a motor application, and if your bus voltage is, let's say, 500 volts, that is going to be your working voltage. If you have a solar inverter with your bus voltage being 2,000 volts, that's going to be you working voltage. And the lifetime at this particular voltage, you can find out by looking at this plot and knowing where it hits the curve, and that's the lifetime of the device.

And the curve, lower curve here, the dashed line, is for optocouplers, and the solid line is for a typical TI device. The plot clearly shows that there's a significant difference in the lifetime curve of TI devices and optocouplers. You can also see that the variation of lifetime from one sample to another sample varies quite a bit for the optocouplers in comparison to TI devices. And the primary cause of such a variation in optocouplers is due to the assembly process, while the well-controlled TI devices do not produce such a variation in lifetime.

So that's about the technological comparison on construction as well as lifetime. Now let's look at-- from the point of performance, look at the performance of these devices. Switching performance and power consumption. Switching performance of an isolator is critical for an application to meet your timing requirements, overall system timing requirements, and also to meet your day-to-day needs.

The general-purpose optocouplers usually do not have any data rates defined in the data sheet, making-- it makes it difficult for you to determine whether a particular optocoupler is suitable for your application or not. Since the optocouplers have current on the inputs, they usually require much higher currents at the input. And, also, since they have open collector outputs, they also end up consuming more current on the output side as well. And to support reasonable data rates, you would-- the devices end up consuming a lot more current than what is usually expected from a digital isolator.

And since the pull-up resistors are used externally, they also dissipate power, resulting in lower efficiency. Even the fastest optocouplers do not have very good propagation delays. And the maximum data rate that you can achieve with the optocouplers is generally limited.

In comparison, TI digital isolators do not need the bias to be different for different data rates. They're usually pretty consistent, and the power consumption only varies slightly. And the data rates that the devices guarantee is also provided in the data sheet, making it easy for you to choose the devices that are suitable for your application easily.

And lower power consumption-- the consumption, power consumption, compared to optocouplers, is significantly lower for digital isolators. And the propagation delay is also significantly lower for digital isolators. And, hence, it is possible to achieve very high data rates with ease for digital isolators.

Here is a simple table, a detailed analysis done from the data sheet parameters for optocouplers and key TI devices. This is the optocoupler with typical load resistor, or the pull-up resistor, and the output, and TI devices ISO7741, ISO6741. They are compared against general-purpose optocouplers. They're also compared against high-speed optocouplers.

So some of the parameters from the data sheet are considered here to determine the maximum asynchronous and maximum synchronous data rates. Asynchronous data rate is a data rate for interfaces like UART, where you do not have a synchronous clock, while the synchronous data rate is for a synchronous interface like Serial Peripheral Interface, SPI. With the data sheet provided timing specifications and yield biasing, you can see that the data rates it can achieve are significantly low in comparison to what can be achieved with ISO77 and the ISO67 devices.

Even a high-speed optocoupler is also still going to have a limit, [AUDIO OUT] while, in comparison, you can see the ISO77 and 67 offer significantly higher data rates. You will be getting these slides, so you can definitely go through in detail on this data.

The next parameter to compare is the Common-Mode Transient Immunity, in short, CMTI. What is CMTI? It is the immunity to the noise that appears across an isolator, which can get into-- couple into the device internal circuit and disrupt normal operation. And the optocouplers typically have only about 15 to 25 kilovolts per microsecond of CMTI performance. In comparison, you can expect a typical CMTI of 100 kilovolts per microsecond for digital isolators.

There are many reasons for this difference, and one of the possible reasons is that the design-- optocoupler internal design is single-ended. There are not many mechanisms to reject common-mode noise. While, in digital isolators, the design is differential-ended, making the receivers having high common-mode noise rejection to inherently reject noise and achieve higher CMTI performances.

And, next, let's compare the input types of optocouplers and the digital isolators. Optocouplers have current-driven inputs, while digital isolators are voltage driven, and they're either CMOS inputs or TTL logic inputs. It is not common to see current-driven inputs on digital devices, devices like MCUs, processors, data converters, other digital devices. You do not see current input product types. You mostly see voltage-driven inputs.

Since the current-driven inputs need higher current, they end up requiring buffers to be interfaced to such inputs, while no such buffer is needed for voltage input interfaces. Since the current-driven inputs also need a lot higher current to offer better performance, while the digital isolators only need about less than 10 microamperes of current to offer a good performance.

It also becomes difficult to operate with low voltages for current input logics, because a small voltage variation can lead to a lot of change in the current, while digital isolators can reliably work for very low voltages. The difference in input capacitance also leads to lower speeds for optocouplers, while the digital isolators don't have that limitation.

Aging and reliability. It is very well known that the light output of LEDs in the optocouplers degrades over time, and this affects multiple parameters of the device, and one of the key parameters is the current transfer ratio. It's a ratio between the input current and output current, which needs to be steady and consistent throughout the life, Ideally, to be able to perform the same. Unfortunately, it degrades quite a bit for optocouplers, and is a function of time due to mold compound color changes.

This degradation in CTR eventually falls to a level where the device no longer operates as expected, thereby leading to higher failures. Such higher failures due to the CTR also yield high FIT rate and low MTBF, leading to very poor reliability of the optocouplers. And these degradations also are not specified in the data sheet. You can see that most of the parameters in the optocoupler data sheet only have a typical value. There is no min/max to cover the aging of the device.

In comparison, the control circuit in the digital isolators are very well trimmed, minimizing performance variation due to aging. And the highly controlled manufacturing process of digital isolators does achieve very high reliability. This also, in turn, leads to very low FIT rates, very low failure rates, and high MTBF. And aging as well is already covered and specified in the data sheet in the min/max specifications. If the device is going to have variation in performance, that's already specified in the data sheet. So if you consider those min/max limits into your system design, you don't have any variation in system performance with time.

So we have compared the digital isolators against optocouplers with respect to multiple parameters so far. I'm going to introduce just a few key TI devices that we recommend to use in place of optocouplers. Like you've already seen earlier, the ISO77XX family is one of the latest and robust digital isolators in the family that TI has. And it offers device in multiple packages and with multiple channel configurations, up to 6 channels. And the isolation rating of the device, VISO, is also pretty high, with 5,000 volts RMS, very high surge rating, very high working voltage of up to 1,500 volts RMS, and very high CMTI. All of this makes the device really suitable for a wide variety of applications. This is isolation-related specification.

Electrical performance is also pretty good. We've already seen the switching performance and power consumption data of this device earlier. We can also see that here. In the interest of time, I'm not going to discuss any further on this slide. You will be getting the slides. You have a look at the devices. And any questions on any particular parameter, do feel free to put that in the chat.

This is one of the high-performance devices from the TI. While the ISO67xx is a similar family as ISO77, with slightly lower isolation ratings, and this device is mostly available with basic isolation. For reinforced isolation, ISO77 is the best family, while, for basic isolation, ISO67 going to be a good fit.

Let's look at the use cases. There are many places where isolation can-- isolation devices can be used. Some of the key interfaces, I'm going to cover here, and discuss how an optocoupler is used in these applications, and how a TI digital isolator is used, and what benefit does TI digital isolators offer in these applications.

UART application. It's an interface typically used for low-speed communication between two devices. Here, in the example schematic, you can see there are optocouplers used to implement UART. You need two optocouplers, two single-channel optocouplers being compared here against the ISO6721, which is a dual-channel digital isolators.

And the optocouplers, you can see that there are pull-up resistors needed at the input as well as at the output, while there are no such components needed for ISO67 except for the decoupling capacitors. And when you compare the power consumption of the optocoupler versus the ISO67, we can see that the current consumption that the optocoupler has is 12 milliamps per channel, while it is only 1.45 milliamps per channel for the ISO6721.

Serial Peripheral Interface, SPI. SPI is usually used for data rates from 1 Mbps to 30 megabits per second. What are the key drawbacks of optocouplers? It's that there are not many optocouplers that are available in multi-channel configuration. You mostly find the single-channel optocouplers in a single package. And if you use the optocouplers to implement SPI interface, you would end up consuming a lot of space and a lot of components. While a digital isolator can integrate full channels easily into a single package, and does not require any external components. And, hence, the space required for a TI is significantly lower in comparison to optocoupler.

Just like earlier, a quick comparison of power consumption of an optocoupler, a general-purpose optocoupler with open collector output and an optocoupler with a totem-pole output. You can see the difference in current consumption.

And I squared C application. I squared C is a bi-directional interface. We don't find any optocouplers that are bi-directional. We do have to implement I squared C discretely for optocouplers, with a lot of external components. While, at TI, we have isolators dedicated to I squared C application, and requiring only the pull-up resistors which is required by the interface itself. And, hence, you can see that the number of components required for an optocoupler-based solution is going to be like 16, while, for digital isolators, it's only about six components. So that's a significant savings in the space as well as overall system cost.

An example I squared C device, the ISO1640. This is one of our latest bi-directional I squared C device, available with different isolation ratings. We can-- since-- in the interest of time, I'm going to skip this slide. So the three interfaces that we looked at so far is UART, SPI, for which you can use a typical digital isolator, like the ISO67 or the ISO77 family, while, for I squared C, the ISO1640 is a suitable device.

Now let's look at other interfaces, the RS-485 in this case. A typical optocoupler-based solution usually has a transceiver separately outside, with a lot of discrete components implemented to achieve the interface, while TI offers multiple integrated solutions where the isolator and the transceiver, RS-485 transceiver, is integrated in a single package. And the devices are also available with differing-- various performance specifications and packages.

The ISO1410 is a high-performance, high-isolation rating device in a bigger package, while the ISO1500 is a cost-sensitive based applications device that offers a very small package for-- both to keep the cost minimal as well as the save space in your system. So the first solution, the ISO1410-based solution gives you about 70% size reduction in comparison to optocoupler-based solution, while the basic ISO1500-based solution gives you about 86% size reduction.

The reliability comparison against these solutions, we've already discussed. The lifetime of TI isolators is going to be pretty high in comparison to optocouplers. And the temperature range that the TI devices is support is going to be significantly higher compared to the optocouplers. And, also, the transient performance, CMTI in this case, is going to be significantly higher for TI devices in comparison to optocouplers. Data rate-- also, the ISO1410 supports 50 Mbps data rate, with very good timing specifications, but it's very rare to find such devices for an optocoupler.

There's a technical document which describes this interface and these devices and compares them to optocouplers in detail. For that, you can refer to the document listed here, "How to Isolate RS-485 for Smallest Size and Highest Reliability Applications." So that's about the RS-485. You can see the dimension of the board on optocoupler-based solution as well as the ISO1500. They're significantly different.

ISO14xx device that we just discussed, it offers very similar isolation applications as the ISO77 that we discussed earlier. You can go to this slide once you have the slide deck. The ISO1500 focused on space-saving and cost-sensitive applications, and that's this device.

Isolated CAN application. Again, the optocouplers need an external CAN transceiver to achieve an isolated CAN solution, while TI devices integrate the CAN transceiver, and offer devices with different performance specifications. ISO1042 is a reinforced performance-based device, while the ISO1044 is a basic and a small-package solution.

Solution size reduction. Like what you observed in RS-485 case, even in the CAN you can see that there is significant reduction from both the reinforced device as well as the smaller basic device. Reliability is going to be similar to what we observed in RS-485 application.

And the propagation delay that is required for the CAN interface is guaranteed in the isolation-- TI isolation devices, while it's difficult to achieve that from a discrete solution based on optocouplers. And you would have to make those calculations to find out if it really meets your application requirements. There's another technical document for CAN that describes these points in detail. Please refer to this document for more details, the size comparison of an optocoupler-based solution and the ISO1044.

The ISO1042 device that we discussed is a reinforced isolated CAN device. It again offers very similar isolation performance, similar to ISO77 family that we discussed earlier. You can go to this slide once you have the slide deck. And the ISO1044 is a smaller size. Space-constrained applications can use this device, ISO1044.

This is the last interface that we're going to be discussing. This is basically our 12-volt or the 24-volt industrial digital inputs. These are the digital inputs that are commonly found in PLCs. An optocoupler-based solution, this is how it looks like. It has external components to achieve current limiting, and also has a very complex circuit to regulate the current to minimize power consumption.

That's an optocoupler-based solution, while a TI solution integrates current regulation inside there, which you don't see any current variation-- any noticeable current variation in the input with a change in input voltage, thereby minimizing the power dissipation in the external components. This is the ISO1211 device. Since the ISO1211 integrates this current limiting feature, you can achieve 74% size reduction in an ISO1211-based solution in comparison to an optocoupler-based solution.

The reliability factors are going to be similar to what we discussed so far for RS-485 isolated CAN interfaces. And, also, you can achieve very accurate current limit that is in-built into ISO1211, thereby limiting power dissipation as well as minimizing the component size of the external components, like the resistors, while the current limit that you can achieve with optocouplers with external circuit is not going to be as accurate, and also going to consume a lot of space and increase your overall system thermal space, as well as poorer thermal performance.

The document described here does talk about these aspects in detail. Please do go to this document. The ISO121x family includes the ISO1211 and the ISO1212, basically a single-channel device and a two-channel device. And the specifications are pretty good, and they meet all the PLC isolation as well as speed requirements, and also do meet and comply the PLC Digital Input Standard, the IEC 61131-2, supporting all three characteristics-- type 1, 2, 3.

Here are some of the additional resources that can be very useful for your isolated design. And hope you can find these documents very useful in designing your system. So, with that, I end my presentation. Now we have about 4 minutes, I believe. We can take up any questions you have.

OK. I don't think we unmute anyone. If anybody has any questions, they can put it in the chat. So we can give it a minute. We have a question here, Kote. Do you have any documentation on reasons for isolation.

Yes. Thanks, Tony. We have some of the training material on the website that talks about various aspects of isolation. One of them does cover the key aspects of the reasons when you need to use isolation. That is, I think, very well described.

You can go through the isolation page on the ti.com website. And the presentation also has the link. You can find the videos on the page itself, which describe why do you need isolation, when do you need isolation, and what applications require isolation.

OK. Second question came in. How we'll receive the presentation. Is it by email, or is there another way for it to be downloaded?

I believe all the attendees will get an email with the link to the presentation. I guess all that, we already provided.

OK. OK, then. We'll close this out then. Thank you all for joining, and I hope you guys have a good rest of the time here. And have a good holiday. Thank you.

Thank you.