EEVblog #517 - Car Airbag Controller Teardown

hi welcome to teardown Tuesday this one has been sitting on my Ted n shelf for quite some time it came in a quite an old mailbag episode now it come that came from by Joey in the UK so thank you very much Joey it is an air bag control unit from a fairly recent model hi owned a car that has seen better days apparently so this could be a really interesting and for those playing along at home there's the part number there and there's another wall it's manufactured by TRW that's the TRW part number and works on a 12-volt system and 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 designed to indicate that the unit must be installed in the car in a certain way because airbags only activate with basically pretty much a front on front on collision or at a certain angle to a front on a collision like that so obviously that means it's going to have an internal accelerometer or sensor in there to you know some sort of inertial switch or something to detect that to detect the crash but I believe old model airbag controllers they did use mechanical inertial in inertial switches or something like that some sort of mechanical device to detect it but all that fairly modern ones including this one I'm sure using MEMS accelerometer so that'll just be mounted on the PCB or it could be mounted on its own PCB and there or something like that we won't know until we take it apart but I also believe that that's not the only 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 mounted around the car so it requires multiple sensors to be activated before this thing will we blow the air bag and like passenger passenger detection switches and all sorts of you know weird and wonderful sensors all placed around the car and lots of algorithmic control inside this thing now I've already I've showed a preview of this in the mailbag 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 clearly we've actually got quite a few connections on here so obviously um you know there's quite a bit of 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 we're going to have to try and lever this board out I think we might be able to lever it out and these pins are really quite interesting as you can see they are not soldered they are actually yacht press fit pins which as the name implies you just press these connectors into the PCB and they just don't hold themselves in place with friction now you might think of you know a bear controllers have to be ultra reliable past many stringent 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 pins like that well as it turns out these that press fit connectors are actually incredibly reliable but there is a lot of art which goes into getting them right and making them reliable so the exact diameter of the pin hole the the plate in and all that sort of stuff in the hole and getting just exactly the right pressure on those little pressed fit pins down in there there's you know a lot that goes into that and yet they would have had to have that approved much vibration and shock testing and all sorts of stuff goes into that but yet trust me um you find these in a lot of ultra high reliability industries where they don't actually solder because solder joints can be brittle they can crack under stress and vibration and stuff like that so it can actually be more reliable to have these press-fit 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 you press fit connectors as well and you can actually see that looks like a some sort of programming port something like that whether or not it's a JTAG port or whether or not maybe it's designed for getting the data out because I believe these airbag continue Mnet's contain and E squared prom in them they actually store the data from any incident ie crash you know so that the investigators can come along read out the data see exactly 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 it and stuff like that so I'd be surprised if there's not an e squared problem inside here somewhere and probably a reasonable amount of processing power as well as I said there's lots of proprietary algorithms which go into these airbag controllers these days and I'm not sure if this thing is going to prize out oh yeah yeah no I thought maybe you 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 tada ah we're in like Flynn look at that Hey look at that huge look at that huge cap on there that's rather surprising and the board is conformally coated you can see that all around here you can see the I did that 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 board in conformal coating like there's no conformal coating over well the top of this chip here and and the cap and everything else so they've clearly someone's gone over that with a brush and just brushed on that conformal coating conformal coating is very common in in in an ultra high reliability device like this because it that keeps out the moisture and from the board and ensures that it works over a huge range of climates because of you know who knows what climates these are air bags in different countries and things like that many different varying climates but yeah it's not a full conformal coating I'm a bit surprised that it hasn't been completely gunked actually but the big capacitor there that's rather interesting that's obviously that device yeah that's the device on the bottom that had the press fit pins there's no electrical connection on those ones but there's the two pins for the cap there and 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 well maybe they ended up putting a shorter cap in but could certainly fit a longer cap in there and what that's for my guess would be 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 or quite a large amount of energy and what that energy is used for Eva Eva 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 because it needs some extra grunt perhaps to blow the airbag but that's not likely because we're in a 12-volt automotive system we've already got you know a big low impedance 12-volt path coming from the main vehicle supply so really you know you don't need it so I reckon that's most likely reason for that is a backup yeah 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 a squared prom as well that would be a you know that would be a requirement of these modules probably to pass Type Approval and things like that they've got a room you know that because in a crash you don't want to crash and then all your wiring going to this thing gets us severed and then you lose power and it doesn't have time to write the data the e squared problem 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 and it probably stringent requirements if anyone has any data you know documents on the requirements for these air bag controllers and please post it because I'm sure a lot of people will be interested in the red tape which goes behind getting one of these things approved 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 there's going to be shot 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 control to ensure that the charges blow on the airbags and that that crash data is written to an e squared problem in here somewhere and the other thing is I'm quite surprised at the amount of processing in this thing I thought I'd have a bit but yeah we've got a large quad flat-pack another one under there or got quite a few qf n type packages around here by the looks of it there's an 8 p NS oh that could be the e squared prom perhaps but yet 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 prising out that's for sure it's even got its own little bar coded part number on there and another 8 PS oh 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 maybe welded stud or something like that it hasn't just been soldered on to there that's for sure and the capacitor in that as you expect not a one hunger brand it's a Nippon chemi-con Brent you know basically one of the world's best capacitors are 84 hundred microfarads 25 volts and it's an LG B's Cirie's and i went and looked that up and sure enough this is a specific series of capacitors designed for airbag applications there you go so probably much more stringent manufacturing or testing requirements or something like that maybe some extra shock and vibration resistance and I don't you know a 105 degree C temperature rated but yeah specifically designed for airbag applications interesting now unfortunately the conformal coating might make it very difficult to read some of the part numbers here but 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 air use any solvent to try and get rid of it or or something like that so if I cannot 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 renesis part renesis are the number one microcontroller manufacturer in the world because they do almost dominate the automotive market or they got a massive share in the automotive micro controller market and it's a h8 SX 1725 series and well you go look this one up I'll provide the links below for these things if you want to check out the data sheets and websites for these but I found a press release for this series the 1700 series from 2007 saying this one is specific specifically designed for in vehicle control application and airbag controllers so there you go another example of where the automotive industry has such clout that in terms of volume and in a 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 J lead coming out the side there and it's probably some sort of a diode or something like that can't see any type markings on the top through that bubbly conformal coating but yet most likely some sort of big-ass diode look at the huge pad on the bottom and how its heat sunk and there's just a little four pin data line choke there to keep all the crap off the data line coming from wherever it is coming from I don't know but yet probably part of the canvas there and this one took a little bit of finding it's a tear Li 87600 surrounding it the big inductors all the caps all those passive parts it's obviously something to do with the power supply and sure enough and it's an Infineon part once again specifically designed for automotive applications and the example application they show in their brochure for this thing couldn't get a datasheet but I got a you know a sales brochure on their automotive stuff specifically for airbag control systems and it is a power management controller pretty much it's got a boost cannot a buck converter in there I think it's got to boost converters it's got a linear regen there it's got a reset watchdog system all in one chip but once again specifically designed for the automotive market and here's in Finian's airbags system solution from their glossy brochure which they give to all the car company executives and design teams and there it is that's what we just looked at the t le 87600 and maybe there's other tele parts in here as well i mean these are the squib drivers for the airbags you can see how tied in these things are I mean like this you know buckle switches down here pressure sensors over here accelerometers and many accelerometers come in here that's a they've got an interface chip specifically for that and of course they're pushing their own I'm Feeny and pushing their own MCU here I'm not sure how many how many design wins they get but I'm sure they get 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 that the components we've looked at so far they've gone for a main renesis at CPU and then some Infineon stuff around that at least one part and as problem wouldn't surprise me if there's a few more Infineon parts in there or renesis parts perhaps the part number on that second largest cord flat-pack part there I do that's tricky but it is quite easy if you view this through the Manta scope at a 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 search it's got 155 4 5 7 - 2 m/s 84 DC 99 1 4 o 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 a two separate devices is not just that one that MEMS accelerometer got ourselves - these are freescale Mme 6800 series this one here is the Mme 68 to one and this one's the Mme 68 5 6 - the datasheet once again very specifically designed for automotive airbag systems it's a spi based to access medium G over damped lateral accelerometer woohoo and it's part of this say for sure system beautiful specifically tailored for the market once again plus minus 20 G 2 plus minus 120 g in a single supply spi compatible timbi digital signed or unsigned spi output 12 low-pass filter options roof 50 Hertz to 1000 Hertz optional offset cancellation all sorts of goodness down here so we have the two one which is the hundred and twenty G on the x-axis and plus minus 25 G on the y-axis and check out the block diagram of this puppy here we go we've got our overdamped our Y sensor and our X sensor in here and we've got a delta sigma converter sine c filter lo various low-pass filters compensation linear interpolation offset cancellation output scaling ah wonderful stuff it's got to build an 8 Meg oscillator and digital regulators and all sorts of power supply stuff and it's got its own internal array one-time programmable array in there and this is a jewel axes one but the other chip of the sixty eight five six is identical to this except it only has the X axes in here it doesn't have this Y axes on the top that part there looks like some sort of SMD do but it's actually a 10 megahertz crystal and the remaining parts on the board once again very difficult to find information but I did get the e squared prom that was pretty easy that's an STM 95 2 5 6 256 K bit a squared prom so that would have the yeah that would be storing the crash data in that thing presumably and this one down in here has got s 50 51 G 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 can bus driver and that's an infant ele six two five oh gee so they did you know at least use some other Infineon parts on here so what's say we rip that e squared 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 are some chip quick solder here and really it was a real dog to get off I almost thought that I killed it almost thought I damaged it but no I managed to get it out relatively intact and put it in my little lump s o ZIF socket here so let's read the contents or try to and here it is excuse the lack of proper screen capture here and all the top bit of it is ffffff of course are my little um you know $30 programmer actually are supported this ST device but look we've got some data and bingo null null null and that looks like some real data there we go ds2 s CSP one ki no idea what that is but it looks like we do have some legitimate data out of this thing and we got some numerical sequences there and of course I didn't really expect to find anything that exciting in here it's not like you know it's just it's um well as I said presumably a part of its function is to store the crash data in here so who knows about the contents but anyway I was able to read it and presumably after a crash if it was involved in a crash you could if you knew how to you could reset the data and reprogram that chip and put it back into use but geez how to be pretty desperate and there you have it I hope you enjoyed the teardown of that reasonably modern airbag controller there and I was a little bit uh surprised at the complexity 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 stuff in these airbag controllers and SuperDuper reliable and they use a lot of specific parts designed specifically by the chip manufacturers for the airbag market which 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 while they do I've worked in the seismic industry where manufacturers provide specific icees designed just for seismic data acquisition you know world-leading delta-sigma converters for example they are specifically designed for the low sample rates and things like that similar in the automotive here although not as sort of specialized really that you could use them as more are 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 that can be used for you know other - stuff more more generic sort of processing and things like that so there you go 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 the comments or the eevblog forum is the place to do it if you like tear down Tuesday please give it a big thumbs up catch you next time you you

Channel: EEVblog

Views: 127,792

Rating: 4.9264989 out of 5

Keywords: airbag, airbag controller, controller, kia, processor, conformal coating, hyundai, Automobile (Industry), Crash, Accident, car, teardown

Id: kcxw850YpVc

Length: 23min 12sec (1392 seconds)

Published: Sun Sep 08 2013