Hi welcome to Tar Down! Tuesday This one has been sitting on my Tar Down shelf for quite some time. It came in a quite an old mailbag episode. Now it come came from uh Joey in the UK so thank you very much. Joey It is an airbag control unit from a fairly recent model um hyundo car that has, uh, seen better days apparently.

so uh, this could be really interesting and and uh, for those playing along at home, there's the part number there and there's another. Well, it's manufactured by TRW that's the TRW part number and uh works on a 12vt system and uh, we'll have a look at how an airbag controller Works Although I'm not sure how much we're actually going to be able to glean from this thing, but one thing we do know for starters here is, look at this forward: Arrow here. Obviously that is uh designed to indicate that the unit must be installed in the car in a certain way. CU Airbags only activate with basically pretty much a front on front on collision or at a certain angle to a Fronton Collision like that.

So obviously that means it's going to have an internal Uh accelerometer or sensor in there to, uh, you know, some sort of inertial switch or something to detect that to detect the crash. but uh, I believe old model uh airbag controllers. They did use mechanical inertial, uh, in inertial switches or something like that, some sort of mechanical device to detect it. but uh, all the Fairly modern ones including this one.

I'm sure use a M's Uh accelerometer so that'll just be mounted on the PCB or it could be mounted on its own PCB in there or something like that. We won't know until we take it apart, but I Also believe that that's not the only Uh sensor in the car for activating these airbags. Don't quote me on this, but I believe there are other, especially in these modern cars. Lots of other sensors uh mounted around the car, so it requires multiple sensors to be activated before this thing will actually blow the airbag.

and uh, like passenger passenger detection switches and all sorts of uh, you know, weird and wonderful sensors all placed around the car. and lots of algorithmic control inside this thing. Now I've already um, I've showed a preview of this in the mail bag before I've already taken off the metal backing plate from this. It just came off with a couple of screws I don't have that anymore, but it's gone.

and uh, clearly we've actually got quite a few connections on here. so obviously, um, you know it. There's quite a bit of uh data coming in and out of this thing and as I said, most likely a lot of those are coming from other sensors within the car. So um, we're going to have to try and lever this board out.

I Think we might be able to lever it out and and these pins are really quite interesting. As you can see, they are not solded. They are actually uh, Pressfit pins. which, uh, as the name implies, you just press these connectors into the PCB and they just, uh, hold themselves in place with friction.

Now you might think, um, you know, airbag controlers have to be ultra reliable past many stringent uh, you know, approvals and type testing and things like that and you might wonder how the hell they can get away with not soldering the like that? Well, as it turns out, these Press Fit connectors are actually incredibly reliable. but there is a lot of art which goes into getting uh them right and making them reliable. So the exact diameter of the pin hole, the the plating and all that sort of uh, stuff in the hole, and getting just exactly the right pressure on those little um, Pressfit pins down in there. there's you know, a lot that goes into that.

and uh, yeah, they would have had to have that approved. Much vibration and shock testing and all sorts of stuff goes into that. But yeah, trust me. Um, you find these in a lot of uh, ultra high reliability Industries Where they don't actually solder because solder joints can be, uh, brittle.

They can crack under stress and vibration and stuff like that. So it can actually be more reliable to have these Pressfit connectors. and they've got another one over there and they've got another big device underneath I'm not actually sure what that is and that's got a few press fit connectors as well and you can actually see that looks like a, um, some sort of programming. uh Port something like that.

Whether or not it's a JTAG port or whether or not. um, maybe it's designed for getting the data out cuz I believe these airbag units contain an E prom in them. Uh, they actually store the data from any uh incident. I.E Crash.

You know, so that the investigators can come along, read out the data, see exact. You know somebody's killed by an airbag or something. Obviously, you know there's going to be an investigation. they'll get the data out of of it and stuff like that.

So um, I'd be surprised if there's not an E prom inside here somewhere, and probably a a reasonable amount of, uh, processing power as well. As I said, there's lots of uh, proprietary algorithms which go into these airbag controllers these days and uh, I'm not sure if this thing is going to prize out. Oh yeah, yeah, no. I Thought maybe we might have to prize out the connectors of the pins, but hang on.

hey, no, that's that's coming out. Pretty easy. Pretty easy. Yep, yep, no problem.

Taada. Oh, we're in like Flynn Look at that. Hey, look at that huge look at that huge cap on there. That's uh, rather surprising.

And the board is conformally coated. You can see that all around here. You can see the I get the right angle of the light. You can really see that it's not completely dipped.

They haven't completely gone and dipped the entire boarding conformal coating like there's no conformal COA over, well, the top of this chip here. and uh, and the cap and everything else. So they've um, clearly someone's gone over that with a brush and just brushed on that conformal coating. Conformal coating is very common in Uh, In in ultra high reliability.

Uh. device like this because it, uh, keeps out the moisture and and uh from the board and uh, ensures that it works over a huge, um range of climates because you know, who knows what climates these. uh, airbags in different countries and things like that. Um, many different varying climates.

But uh, yeah, it's not a full con conformal coding. I'm a bit surprised that it's hasn't been completely gunked actually. but uh, the big capacitor there. That's rather interesting.

That's obviously that device. Yeah, that's the device on on the bottom that had the pressfit pins. There's no electrical connection on those ones, but there's the two pins for the cap there. and uh, they've gone to a lot of trouble to mount that cap in its own big custom housing.

It's not very long, it's not as long as the entire thing. Um, well, maybe they ended up putting a shorter cap in, but it could certainly fit a longer cap in there and what that's for? my guess would be um, well, it's You know, it's obviously not for regular power supply smoothing, right? You can bet your bottom dollar on that. When you've got a capacitor that large, it stores a massive well. quite a large amount of uh, energy and uh, what that energy is used for either.

either it's directly on the supply rail, it's actually powering the supply. Rail And then if there's a power fire in the car, there's still enough power on the rail to keep the circuitry going to blow the airbag. or whether or not it's just the energy storage device that then you know cuz it need need some extra grunt. perhaps to blow the airbag, but that's not likely because we're in a 12vt automotive system.

we've already got. you know, a big low impedance 12volt path coming from the main uh vehicle. Supply So really you know you don't need it. So I reckon that's most likely reason for that is a backup um you know is to supply the power to all this to keep it going after the crash because after the crash as I said, you have to write to that E prom as well.

that would be a uh uh, You know that would be a requirement of these modules probably to pass type approval and things like that. They've got to. You know that cuz in a uh crash you don't want to crash and then all your wiring going to this thing gets uh severed and then you lose power and it doesn't have time to write the data to the E Squ prom or something like that? I Don't know. It's unlikely it doesn't take much time to write, but maybe that's part of the uh, probably stringent requirements.

If anyone has any data um, you you know documents on the requirements for these airbag controllers, then please, uh, post it cuz I'm sure a lot of people will be interested in the Uh red tape which goes behind getting one of these things approved. um I Can't see any type of approval marks or anything like that, but of course they would very well be. And that may be another reason why this capacitor is in its own little protective cage like that is that there's going to be some Shock uh uh, there's going to be sh some shock protection inside that I mean they've got the leads. You know there's going to be some compliance in the in the leads there and in this plastic housing.

So in a big accident like this, they're protecting the capacitor as the supply of the voltage to this airbag controller to ensure that the Uh charges blow on the airbags and that that crash data is written to an E Prom in here somewhere. And the other thing is I'm quite surprised Ed at the amount of processing in this thing I Thought it would have a bit, but uh yeah, we got a large quad flat pack, another one under there. We got quite a few Qfn type packages around here. by the looks of it.

uh, there's an 8 Pino that could be the E Prom perhaps? Um, but yeah, let's take a closer look at the board missing device over here. don't know what's going on there. I'll tell you what. that capacitor took some prizing out, that's for sure.

It's a even got its own little uh, barcoded part number on there and another 8. Pin So maybe the crash data inside there? perhaps. But there we go. We can get a good look at all the components now and the connection for that capacitor looks like it's some uh, maybe worlded stud or uh, something like that.

It uh, hasn't just been solded onto there, that's for sure. And the capacitor in that? uh, as you expect, not a one hung Low brand. It's a Nipon Chemicon uh brand, you know. Basically one of the world's best capacitors.

Uh, 8,400 microfarad, 25 volts and it's an LGB series and I went and looked that up and sure enough, this is a specific series of capacitors designed for airbag applications. There you go. Um, so probably much more uh, stringent manufacturing or uh testing requirements or something like that. Maybe some extra uh, shock and vibration resistance and I don't you know? 105 C temperature rated.

but um, yeah. Specifically designed for airbag applications. Interesting Now, unfortunately, the conformal coding might make it very difficult to read some of the part numbers here, but uh, I'll have a go and I'll probably try and scrape it off if I have to. I'm not going to have time to, you know, use any solvent to try and get rid of it or or something like that.

So if I can read them at a certain angle under the microscope with light at a certain angle, then I'll try and do that. Otherwise I'll scrape it off and the main processor down in there. Well, no surprises. It's a renais Part Renais are the number one microcontroller manufacturer in the world because they uh, almost dominate the automotive.

Market Or they got a massive share in the automotive uh micro controller market and uh, it's a H8 uh, SX 1725 series and well, you go look this one up. I'll provide the links below for these things. Uh, if you want to check out the Uh data sheets and uh websites for these, but I Found a press release uh for this Uh series, the 1700 series from Uh. 2007 saying this one is spec this series specifically designed for in vehicle control application and airbag controllers.

So there you go. Um, another examp example of where the automotive industry has such clout that you know in terms of volume and uh, you know, um, profit margin and stuff like that that these companies bend over backwards to design specific chips and specific series. And as you saw a specific type of capacitor directly for these applications, they target them precisely. Unusual.

It's a two pin package, one large pin on the bottom there, and one uh J lead coming out the side there and it's probably some sort of diode or something like that. Can't see any type markings on the top through that bubbly conformal coating. but yeah, most likely some sort of big ass diode. Look at the huge pad on the bottom and how it's heat sunk and there's just a little four pin data line choke there to keep all the uh crap off the uh uh data line coming from wherever it is coming from.

I Don't know, but uh yeah, probably part of the uh can buas there and this one took a little bit of finding. It's a T 8760 V and uh, as you can see by the components surrounding it, the big inductors, all the Caps all those passive Parts It's obviously uh, something to do with the Uh power supply. and sure enough, um, it's an infinion part once again, specifically Uh designed for automotive applications. And the example they showing their Uh brochure for this thing couldn't get a data sheet but I got a, you know, a sales brocher on their Automotive stuff specifically for airbag control systems.

And it is a power management uh controller Pretty much it's got a boost. It's got a Bu converter in there I think it's got two boost converters. It's got a linear regag in there. it's got a reset uh Watchdog system all in one chip, but once again, specifically designed for the automotive market.

And here's Infini Airbag System solution from their glossy brochure which they give to all the Uh car company Executives and design teams. and there it is. That's what we just looked at the Tle 8760 and maybe there's other Tle uh Parts in here as well I mean these are the squib drivers for the Um airbags. You can see how tied in these things are I mean look, there's you know Buckle switches down here, pressure sensors over here, accelerometers and many acceler come in here.

that's A. They've got a an interface chip specifically for that and of course they're pushing their own Infinium pushing their own MCU here I'm not sure how many, uh, how many design wins they get, but I'm sure they get uh enough, but that's what's inside their particular airbag ECU solution. but it seems like TRW have gone for a mix at the very least, just at the components we've looked at. Uh, so far, they've gone for a main Renaissance CPU and then then some infinion stuff around that at least one part and there's Pro Wouldn't surprise me if there's a few more infinion parts in there or Renaissance Parts perhaps the part number on that second largest Uh quad Flack pack part there I That's tricky, but it is quite easy if you view this through the Mantis scope at a uh, shallow enough angle with the light.

There we go: It's an St part and I can't find any data on that one again at first, uh, search it's got 155 4572 Ms 84 DC 99140 V6 version 6 perhaps I don't know, but it's definitely an St part in Bingo We have ourselves the accelerometer down here, but I'm surprised that it's two separate devices. is not just one mems acceler on got ourselves two. These are free Scale: MMA Uh 6800 Series This one here is the MMA 6821 and this one's the MMA 6856 to the data sheet. Once again, very specifically designed for automotive airbag systems.

It's a Um SPI based 2 AIS medium G overdamped lateral accelerometer. Woohoo! And it's part of their safer Shore system. Beautiful. specifically tailored for the market once again.

Plus - 20g to plus- 120g uh, you know, single Supply SPI uh compatible Uh 10bit digital signed or unsigned SPI output Uh 12 low pass filter options woo 50 HZ to 1,000 HZ optional offset cancellation All sorts of goodness down here. So we have the 21 which is the 120g on the Xaxis and plus - 25g on the Y AIS And check out the block diagram of this puppy. Here we go. We've got our overdamped Uh Y sensor and our X sensor in here and we've got a Delta Sigma converter, S C filter, various low pass filters, compensation, linear interpolation, offset cancellation, output scaling Ah, wonderful stuff.

It's got to build-in 8eg, oscillator and digital regulators, and all sorts of power supply stuff. And it's got its own Um internal array onetime programmable array in there and uh, this is a dual Um axis one. But the other chip, the 6856 is identical to this, except it only has the x-axis in here. It doesn't have this y- axis on the top and that part there looks like some sort of SMD Dio but it's actually a 10 MHz Crystal and the remaining parts on the board.

Uh, once again, very difficult to find information. but I did get the E prom. that was pretty easy. that's an St M 95256 256 kbit E prom so that would have the that would be storing the crash data in that thing presumably and this one down in here has got S50 51g on it and I have not been able to find any data on that one so sorry, no idea and that one there.

No surprises for guessing that's a cam bus driver and that's an Infinium T 625. So they did. Uh, you know, at least use some other Infini on here. So what's say, we rip that E prom off and see if we can read it, huh? It's worth a shot.

Well it really wasn't nice getting that chip out with that conformal coating on it. Let me tell you, it was real difficult I used uh, some uh chip Qui uh solder here and really, it was a real dog to get off. um I almost thought that I killed it. almost thought I damaged it but no I managed to uh, get it out relatively intact and uh, put it in my my little um so Z socket here.

so let's read the contents or try to. And here it is. Excuse the uh, lack of proper screen capture here and uh, all the top bit of it is FFF F ff of of course my little um, you know, $30 programmer actually uh, supported this St device but look, we got some data and bingo look null null null and that looks like some real data. There we go.

d S2s Csp1 K I Have no idea what that is, but it looks like we do have some legitimate data out of this thing and got some numerical sequences there. and uh, of course I Didn't really expect to find anything that exciting in here. It's not like you know it's it's just it's um, well, as I said, presumably a part part of its function is to store the uh, crash data in here, so who knows about the contents. But anyway, I was able to read it and uh, presumably after a crash.

If it was involved in a crash, you could, uh, If you knew how to, you could, uh, reset the data and uh, reprogram that chip and put it back into use. But jez that' be pretty desperate and there you have it. I Hope you enjoyed the tear down of that reasonably modern airbag controller there. and uh, I Was a little bit surprised at the Uh complex of this thing.

but you know these modern things. more and more standards. More and more algorithms go into detecting the things and stuff like that. So uh, you know, fairly.

Advanced Uh. stuff in these airbag controllers and super duper reliable. Um, and they use a lot of specific Parts designed specifically by the chip manufacturers for the airbag Market which uh, you know it isn't surprising in the automotive industry, but if you're not used to that sort of Industry then you go. You know, why can't they design a special chip for me for my industry? Well, they do.

I've worked in the Uh seismic industry where Uh manufacturers provide specific Ic's designed just for seismic data acquisition. you know, World leading Delta Sigma converters for example that are specifically designed for the low Uh sample rates and things like that similar in the automotive here, although not as sort of uh, specialized really that you could use them as more generic Parts Like the main processor here, for example, isn't just for airbag controls, that's just one of the recommended applications. They also recommend it can be used for um, you know other Dash uh stuff more uh, more generic uh sort of processing and things like that. So there you go.

Um if you do have any info on some of the parts which I couldn't identify in there, please leave them in the comments and if you want to discuss it uh, the comments or the EV blog forum is the place to do it. If you like tear down Tuesday please give it a big thumbs up. Catch you next time.