 Hi, on MPI. Hi, on MPI, brought to you by DigiKnade. For this week, it's Analog Devices Lady. What is the new product introduction of the week, this week? This week, we're going back to ADI. We kind of did a couple other brands, but now we're back to the classic. So ADI, this week's I on MPI is, and it's a blank chip. It's their I-Coupler, I-Squared-C Galvanic Isolation chip, which is the ADUM, so I said LT. They also own linear, but ADUM 1252 and the 1253. So these are bi-directional and unidirectional I-Squared-C isolators. They are specifically designed for electrically isolating the I-Squared-C controller and peripheral. There's two versions. One has a bi-directional SCL pin. It's a little bit more expensive, but supports clock stretching and multi-controller mode and the less expensive, I think the 53 is unidirectional. There's one controller, one peripheral, there's no clock stretching. Okay, so isolation, when do you need it? Well, there's three basic usage, although one of them is two usage. So hazardous voltages are noise, so industrial or robotic usage, where there's a lot of high voltages or there's a lot of electrical noise that you're dealing with and you want to isolate your motor power supply and ground totally from your sensor power supply and ground. You might want galvanic isolation. Secondly, medical devices. So a lot of medical devices, they're in literally messy situations. There's a lot of liquids and fluids and they're getting kicked over and they don't want to have anything accidentally connect a power supply to the sensor that connects to somebody's EKG. They often have high sensitivity requirements. Again, you don't want a lot of noise. And then also regulations, especially for power equipment, there might be a legal requirement for you to keep grounds and power supply separate. This is where you want truly electrical separation, not just like a little ferrite bead to kind of clean up the power supplies, but there's literally no electrical connection between the ground and power on other side. Here's an example, especially like you're doing a robot or a medical device. You have an ADC that you really want a nice, quiet power supply. You have an analog ground and analog power and you want to be separated from your microcontroller or microcomputer that's running at 3.3 volt power and logic and has an earth ground and maybe a messier power supply. This is where the ADUM 1252 and 53 do an excellent job. What's interesting is that the ADUM series uses a galvanic isolation that's not an optocoupler. This is kind of what a lot of people think of when they think of MIDI has isolation. There is a package and they're usually kind of chunky packages. There's literally a light and a photo detector and then signal is sent, usually digital signal. There's maybe some cleanup that helps transform the digital signal into the right LED output and then the receiver is a photo transistor and maybe there's like a Schmidt trigger or something to give you some hysteresis control. The whole thing is potted and so this gives you full actual isolation because the light doesn't pass current and there is no electrical connection between the input and output. The problem is that often these well first off they're not bidirectional obviously they're unidirectional. You'd have to have a separate optocoupler for the other direction. You'd have to have support circuitry to switch directions and all that good stuff. Second, they tend to use a high current because you need to have the LED turn on nice and fast. And sometimes the photo detectors aren't very fast either and so you'd have to get a special version if you're going into like the high kilohertz megahertz rate. So analog devices have the eye coupler series and the way this works is it uses instead of an opto isolation it uses an electrical isolation using a transformer. So if you look at and this would be great under the electron microscope nanographs by the way, if you decap the chip there's literally two halves with little coils that are created by using a standard wafer technique but then adding a polyamide insulation layer and then another coil on top. So this is like kind of half circuitry, half post circuitry manufacturing technique but they've been doing this for like two decades and they've gotten really good at it. And you can see there's two kinds of coils. So there's some ADUM chips that do power and you can see in the middle image there's two bigger coils and then four smaller coils. So that is a chip that would do both power and signal transmission but the chip we're talking about don't do power transmission so you do have to supply the power and ground on either side. They'll say that our USB isolator that we sell in the Adafruit shop we have two chips and one does data and one does power and the power one does this. So we're talking about the electrical isolations like a mini transformer and DC DC converter to give you five volts on either side of the output from the five volts input but again fully isolated. The only thing is you're like, wait a minute you know transformers, I know transformers they don't pass DC they only pass AC that's why they're used for AC transformation from you know you know whatever a couple thousand kilovolts down to your home or 240 and then from your 120 or 240 down to 12 volt AC although we tend not to use transformer based power supplies as much these days they're used in some situations but you need to use AC you can use DC and so what you need to do is convert that DC or I mean it's not DC it's digital signal but it has a DC component it's not true AC convert that to AC and then decode it and so if we look here again this is what this is mostly what the circuitry is doing is actually handling that encoding and decoding bidirectionally okay there's also some extra circuitry in there that I thought was kind of nicely added in they had it a added a hot swap controller so if you know you know if you're doing this safety isolation you probably also want to make sure that you don't end up with a stuck I squared C bus which absolutely can happen if you like plug in a device if there's a wire that's jiggled or whatever you have your you know something come in at the middle of an SCL pulse can get very confused because you really want it it wants to see eight SCL pulses before it you know knows what to do next and so on one side there is a a pre-charge and a glitch filter so it will determine when you're actually at a stop condition on the I squared C bus and then it will connect the two sides together so you can also use it as a hot swap controller which is which is kind of nice like it's like a two four you don't need a second hot swap controller as well there's also an undervoltage lockout so if I think you can use either you can use either side as a level shifting I squared C converter 1.8 to 5.5 volts so either side can be 1.8 to 5 volts and you can shift up or down in addition if you go below 1.8 volts there's a lockout so you won't accidentally have them you know have an undervoltage affect the signal on the opposite side of the galvanic isolator. While this chip is I squared C there are different isolators available from you know USB, LVDS, amplifiers, RS232, SPI so you know or ADC or CAN even so you know this is specifically for I squared C it's really only designed for I squared C please don't try to bush it into CAN bus or something but if you do want isolated CAN check out the I coupler series they've made like they've kind of you know cooked this technology into every kind of isolation transform or you could possibly need. Yeah both versions so again one is a little bit the 1253 is a little bit less expensive unidirectional SCL pin 1252 is a little bit more expensive but has bidirectional SCL for when you have multi controller or clock stretching. All right we have a really good video we're going to use. That's right. Hi Dave. Hello Mark. You know we have been building and improving our digital isolators for years and I still get questions from people about whether our installation is as robust as an opto coupler it's like gossip it just keeps coming around. Yeah it really is frustrating after all the materials research we've been doing it'd be really great if we had some dynamic way of showing how robust the insulation really is. You know I think I have just the thing in the lab we can do a side-by-side transient isolation comparison between opto couplers and digital isolators come on let's go do this. Okay so what we have here is one of the most powerful surge testers on the market it's up to 24 kv and it will deliver up to 40 joules of power on every pulse that is enough to ruin your whole day and we also have a high-speed camera to catch any failures. Is this the machine that does the 1.2 by 50 microsecond pulse that the agencies use? It's exactly the same and VDE requires a 10 kv pulse as a proof of reinforced insulation so we're going to start with a 10 kv pulse. There you go. Yeah but we all know that the opto coupler is going to pass this test. Yeah but fair is fair and we really need to test both of them. All right just make it quick. Let's put in the digital isolator. Well we know that both opto couplers and digital isolators will pass this test that's where we get the questions. Opto couplers claim to be much better than the standard while people worry that digital isolators are just barely passing. Well it wasn't a very exciting test I'll grant you that but what do you say we turn this machine all the way up and really test the limits of these technologies all the way? Sure 24 kv. What did I tell you? And here's the opto coupler. Okay 24 kv here we go. Now that was an impressive failure. That blew that opto coupler clean in half. Let's look at that again in slow motion. I would say that result is a pretty clear rebuttal of the gossip. Digital isolators are as capable as opto couplers they have matched and even surpassed them in critical safety parameters like transient withstand. Well my work here is done. Make sure that you lock the lab on the way out and sort of clean this up the lab manager likes it tidy in here.