Hi time for another random Twitter question and rather, just, uh, try and answer it on Twitter. I thought, hey, some people might find this interesting as so. I'd do a video on it. The question comes from Puria Solutions if I've got that right.

Llc. so obviously a company uh, can anyone help me out with a part Id cross reference? Okay, so what we have here is a photo of a Sop 23 uh part with some capacitors and stuff around it and resistories. and we need to identify this part. So how do we go about doing this Now The first thing you should do is, uh, try and sort of like buzz out the circuit like obviously we've got a pin here and that's going off to this resistor here, which looks like it's either a pull-up or a pull-down resistor because it's going to a huge pad here, which is almost certainly some sort of power pad.

Then we've got another signal trace going off here under this component here. and then we've got another pin here, which once again goes off to some caps here with some Vias dropping down. So this is obviously a power in or power out. So whenever you see a small little sot 23 device like this with the capacitors right next to it like this that are obviously going down to ground and power here, either powering or power out, you know that this is some sort of regulator.

Now there's two types of regulators. Of course, there's linear voltage regulators and there's switching voltage regulators. Which one is this? Well, we don't know unless we look at this component down here. Now from experience, I know that this symbol here is the Coil Craft symbol.

And you go, look out the Coilcraft website. They make inductors. They're one of the major manufacturers premium manufacturers of inductors and you can tell it's an inductor by looking at it physically. It's a shame we don't have like a bigger zoomed out photo.

but uh yeah, you can tell by the shape with the corners like that that is the shape of an Smd inductor. And obviously there's a giant pad here. And they've got all the thermal reliefs coming out here here, here, here and here. So whenever you see an inductor next to what something that you think is a voltage regulator, you know.

Aha, it's not a linear voltage regulator, it's a switching voltage regulator. This package, if you didn't know, is called a Sot 23 and you should know. You should have like a have a chart on your wall of like all the different packages until you actually learn exactly what they are. And it's a 5 pin 23.

Three here and two here. There's nothing in the middle here. You can actually get six pin stock 23s of course the software. The Classic.23 is only a three pin jobby and that's usually you know, a transistor, a Fet, a diode, or dual diode or something like that.

So obviously we're looking for a switching voltage regulator. This is the switching inductor here. Uh, this resistor up here is either a pull up or pull down for some sort of enable pin for the chip. So obviously this pin I would say is the enable pin.

This pin here. This is obviously going under the inductor, so this would be the sense output line that I'll show. We'll look at a schematic for a switching regulator in a minute and you'll see that there's a it has to monitor because it regulates. It can't regulate unless it knows what the output voltage is.

So that is obviously the output. uh, sense line there. So this pin here is the output pin. I'll show you the schematic in a minute.

But yeah, it basically is the output pin which goes to the inductor. It's not the output, the final output voltage that comes from the other side of the inductor down here. and that's where this pin is tapping off here. This part down here is the output.

Okay, so these are your output capacitors here and your output capacitors will be going to ground. So obviously this is your ground here. Now if this was just the ground on its own and you just had one via here, that's pretty high inductance. that's bad.

Board layout, Everything else right? not good. but obviously look, it snakes under the chip now you can't see it. But obviously that ground point connects down to here. So we've got some more vias here which stitch your ground line which you need.

It's important. So the more vias are, the lower your inductance to your ground and power that you're trying to stitch to and you'll probably find almost certainly. We've accounted for all these other pins. So obviously that leaves this pin here.

and I guarantee that this pin is the ground pin and that's connected through under here like this. And of course, if you had the physical board, you could measure that. So we've got output capacitors. This is obviously the enable pin here.

It's nothing to do with that power because you wouldn't have it running through that tiny trace like that. So obviously this is our input pin here because these are our input capacitors and these are the two input vias. So if you measured your voltage here, so I don't know how this person has come to say, oh, come to suspect this, uh, chip here, Um, but yeah, obviously you know thou shall measure voltages. Number One rule of troubleshooting.

So you know they probably know that this is. they probably already know that this is some sort of regulator. Anyway, we'll just assume that we didn't know, but now we know it's a switching voltage regulator just by inspection by the topology of what's going on here. So we're now looking for a So our search begins for a Sot 23.5 switching regulator with the pin out we've discussed.

it's got to have the pin out. Obviously, there's going to be a whole bunch of different pin outs, especially for switching regulators. You'll get a whole bunch of different uh pin outs now. First of all, it's not going to be as easy as just searching that part number on top of the chip: 1 capital A lowercase A 3q You search that and well, we've got some uh buy skinny women dark blue jeans online.

Yeah, no thanks. So the next step would be to search an Smd code database Because Smb codes are a real pain in the butt and there are databases out there. They're not always accurate, they don't always work. In fact, I find in most cases they they don't work.

But it's worth a shot just in case. Okay, so here's one particular one. You can search Google for Smd code database or something like that, and there's there's a bunch of them out there. I just found this one and it gives you all this and we can go into.

Sure enough, we can go into one A here A A which is what we had. Okay and whoa. They just happen to be linear voltage regulator Ics, but we know this is a switching regulator. It's got that inductor next to it.

it's that is switching topology. Definitely, as we'll see in a minute on a schematic. let's just search this Ixus one. Oh goodness, I can't even find either of those, right? Look, wait, don't even bother wasting your time.

Okay, what we're going to do is go into Google here and I'm going. I'm going for broke here. So I'm going to put in Sot-23-5 and you have to put the dashes in there because that's just the usual um, syntax with these things. It's Sock 23-5 The five indicates you've got five pins.

Magic through the magic of Google. We've already got. Look at this Melsa directly into the category: Sot 23 5 switching Voltage Regulators. So let's click on that and we're in.

Like Flynn. Look at this. It's already put us into the switching folder voltage regulator, parametric category and it's given us the package case here. The Sot 23.5 Winner Winner Chicken dinner.

Okay, otherwise you could have done this manually on Mouser Dgk Element 14, whoever your favorite catalog supplier is. And when do we get off the bat here? We've got a Texas Instruments jobby lm3671 so we'll open the data sheet for that. So yeah, you just want a couple of different like data sheets from one. Then we'll get the Tps which is a more modern uh Ti part and then we'll go down here.

Nishimbo. I've never heard of Nishimbo. Okay, we'll open a Nishimbo data sheet, shall we? Um, and these are all switching. You know this is a buck regulator, right? So we're all good.

Uh, Analog Devices Jobby, we'll open that. Max Linear Mac. What's a Max Linear? I don't know. We'll open that.

Um, geez, 19 000 stock. Haha. No one's buying the Max Linear and Diodes incorporated down here. Okay, so that's a good selection.

They're almost always a step down unless you know, like, 95 percent of cases. Unless you specifically need to switch up for something, generally you're switching down with Uh. Regulators. So anyway, here's the topology I told you about before.

So sure enough, right? we've got our voltage in. There's our input filter cap, and then we've got that enable pin that we saw with that, uh, resistor there. And then we've got our inductor here. You remember how I said, like I should have said, that was the switching output.

but I just said output. Okay. And then as I said, we've got that feedback line. so it knows how to regulate the output voltage.

It can measure it. So what we want is the actual Uh pin out. Right off the bat, you can tell Pin Four here and Pin Four over here. Sorry, My cursor is small.

I've got a capture problem. I I do actually have a big cursor on this screen, but it's not capturing big. If anyone knows why, let me know. Windows 10.

Um, using Xsplit. I? I don't know. Um, it does the same on Obs as well. So yeah, I don't know a video driver thing.

So obviously the Fb pin here. Pin Four: Um, yeah, nah, that's a that's a Yenna, right? We know that's our voltage input. Okay, So right? off the bat, this is not the chip for us. Next here we go.

Once again. Same same topology here. We've got the enable pin. Everything else.

Once again, not. We're not even in the ballpark. The switching pin here. whereas it's down here like this.

No. and these are top view of course. Make sure you you know they're almost always top view. Um, and we've got obviously the top view of the Uh chip here.

So nope. Next Nishimbo. Every time we do one of these videos, we find like it's in just some new obscure brand. Oh, there you go.

There's the input block diagram for those playing along at home. Very cool. You can see the topology there. and once again, this is a different pin out.

Look at this. Pin four is actually the V Out pin. Well, we know that's not V out. We know it's V in.

And what's pin Three down here? Pin three is the chip enable pin nut. So once again, what's what's Pin One the input pin. So no, once again, we're well off. Next up, we've got this linear technology jobby.

Oh, hang on. I might have been wrong. I might have guessed wrong here. Um, have I because check.

Check this one out right? Look, Pin Three here is the switch. Okay, so that goes off to our inductor. So that's a way to win a chicken dinner. Pin Four over here is V in right? Sure enough, that's our V in five though is feedback.

So our feedback comes like we, we don't know. Unfortunately, we can't see where that trace goes. Would have been better if we had a larger photo, but I could be wrong. and then pin one here is the run pin.

I just thought that you know this would go under here and then it would go to this pad here. but maybe maybe I'm wrong. Maybe it's maybe it's this or coming down all the way so we're very close. If not, we've already found the actual Uh pin out.

Whether or not we've found the actual chip. It doesn't matter at this stage because you remember the person asked, uh, that we if we could find an equivalent Uh part. As long as you get uh, the right pin out and you know they're roughly the similar sort of frequency and stuff like that, you're probably going to end. They're rated at the uh, correct, uh output voltage and these are not adjustable voltage regulators like you have to actually specifically get like this is a like this is a 1.5 volt part.

This is a 1.8 volt part. For example. these are fixed because there's no resistor divider in the feedback here. If there was a resistor divider, you know.

Aha, the it's set to. the output voltage is set by some resistors over here. Um, and then it's You know it's adjustable, but it could be adjustable. Maybe maybe I'm wrong.

but so next. Max Max Linear max power. So what have we got here? See? this is interesting. This actually shows like a a filter network here actually on the voltage feedback pin.

So this is obviously an adjustable uh Jobby here. But anyway, let's uh, let's have a look at the well. We can just go by the pin numbers now. Uh, Pin three here.

Yep, Pin three is correct. it's our switching output. Pin five is our voltage feedback. Okay, Pin four is V in.

Yep, Um, Pin two is ground. Looks like pin two is always ground and uh, pin one is the enable pin. Once again, it's the same pin out as the other one. So maybe maybe maybe maybe this is actually and a part of the adjustment and the other resistor is somewhere else off out here.

which we can't see. So if it is this uh, topology, but yeah, like this could certainly be running under the inductor and it could be going off into la la land, somewhere else into some microcontroller which enables um, the thing or something like that. So obviously they they haven't tied the enable Uh pin. Obviously, you know whether it's this or this, it is going off, uh, somewhere.

And they you know, I assumed at the start that this was a pull down, but I don't know. I'm shooting this video As I go along, I don't actually know if we're actually going to find anything here as like an exact match. So either it is a fixed voltage regulator Um, and this is the enable pin and this is the feedback pin from the output of the inductor here or it's an adjustable regulator and this is the enable pin and this here and this resistor is part of the feedback voltage divider network and in this particular case, if it was, if it is an adjustable one, it might be harder to find a direct equivalent. Uh, because you're dealing with um, you know the the chip.

the formula for calculating the voltage reference and everything internally could be very different. uh, between devices even though they're identical pin out. So you could certainly come a gutsy there by thinking oh yeah, I can just throw in any adjustable one if it's a if it's a fixed voltage regulator one. Yeah, you can probably get away with just pretty much throwing in any one and it's probably going to work.

You know it might not be as efficient or whatever because the inductor values and capacitor values aren't matched for you know, that particular frequency of that device, the particular switching frequency, but you know it's it's probably going to work. We've got one more to try. Uh, Diodes Inc. But it's actually Bcd.

Um, so I don't know. Diodes Inc bought Bcd. I've never heard of Bcd, another name that we haven't heard of uh before. so let's have a look.

Uh, no. Pin Five? Vn, Pin Four? Shut Down? No, No. So obviously the closest we've gotten is this Max Linear joby and this linear technology One the synchronous shutdown one is a fixed regulator because there's no output adjust voltage divider and the other one is adjustable. So yeah, Unfortunately, I don't think we're going to get any further than that in this video.

unfortunately. Um, that's that's probably the best we do unless we can get like a larger photo and see where this trace is going off here because that will tell us if that goes off to another resistor which is then on the output. So if there's another resistor here like this, please excuse the crude of the model that goes to the output here that goes to the output pad of this, uh, in inductor switching inductor over here. If there is another resistor there like in in series with that, then that will be um, an adjustable voltage regulator in here.

So we didn't quite answer Puria Solutions uh, question here. sorry about that, but you know there's only like so far you can go. But hey, leave it in the comments down below. somebody may have used this part.

They may be able to decode, or, uh, recognize this number. Like, I could probably put a bit more work into trying to decode that Smd part number. But generally speaking, Um, yeah, you're not going to do that well. And by the way, if you do want to find them, they're like usually like down in the bottom of the data sheet somewhere.

Let's say no, this one doesn't even have it code marking they they they can be at the top too. They can have like code markings and stuff like that. Let's see if I can find an example Here we go. I usually expect it to see somewhere like that.

It would tell you what the actual number is, but I don't think this data sheet has it. Linear technology. Here you go, Linear Technology has it S5 part marking. There you go, it'll have Lte2 on it.

um so and or Lte3 Lte4 for it looks like the different Uh voltages. So at the moment I guess this is uh, Schrodinger's switching regulator. We it's it's both a an adjustable and a fixed at the same time. It's only when we open the box.

uh do we find out which one is which breaking news I asked on twitter and he replied and we've got a photo of well not the entire board but we can now see what's going on here. Unfortunately it's only low resolution. uh but I've like upscaled it but it's good enough for Australia. We can now work out exactly what's going on here.

And sure enough, yes, my original guess was wrong that this was the enable pin. Uh, this is actually the feedback pin. This is pin. Five, so we're talking this one over here and you can see that it goes to the resistor to ground as we saw before.

But it also goes around here like this to a resistor which then goes to the huge output pad here. No, it's not an inductor, it's a huge, oh every trace is an inductor. But let's not go there. the huge output pad here which is like this.

it looks like we have another cap. there, is it? So as we said before, these are our output filter caps to ground and yep, it's tapping off that. so it is a voltage divider there. So this is an adjustable voltage regulator so that makes it a bit more difficult to actually find a suitable replacement for it.

Yeah, this pin here. pin number one is the enable pin and it goes under here. under here. you can see it, It comes out there and it goes off.

and I don't know somewhere down here it's being controlled by something for whatever reason. start up or and mod. You know some part of the circuit's been enabled or disabled. Something like that.

I forgot to mention it's a vehicle data recorder that hooks up to the can bus in a car. So there you go. Um, this is well and truly solved. It's adjustable.

So what we're looking at now is this is, well, a pin compatible. Now This would be a very different video if I actually had the board, I'd be able to. Well, the next thing I would do. Um, if I'm the poster, I would, um, measure these two resistor values or you can get the values off the top and then you can try and work out if you don't know already, for whatever reason, what the output voltage is supposed to be, this one here, for example, is 1.8 volts with 800 milliamps capability.

Um, yeah, you know you're looking at like half an amp sort of tops for like, a sort, uh package like this. But yeah, you need to work out the output voltage and then um, you'll be able to get the equations down here because it has to do with the internal reference voltage. There it is there. you've got your internal voltage reference, so that could, uh, potentially vary between, uh, different brands and different uh types of variable switching nut chips.

So the calculation to calculate the output voltage based on the resistor divider could change. So, inductor selection and all this, you know, choosing your inductor and capacitor values and stuff. they're going to change. As I said, depending on the switching frequency.

Uh, there can be vast differences in switching frequency between chips and that could really matter. But as I said, you know, if you chose a different brand, it's probably it's at least going to do something. you know you might get more ripple on the output or whatever might not be as efficient. A different part of the efficiency curve or something like that.

But and they're set in the output voltage there v out 0.6 volts. See, that might be like 1.25 volts for example. Um is also common. So once you determine based on those values that this is given your expected output value, then you know.

Aha, I've got the formula I need to then go and look at equivalent data sheets. But the unfortunate downside of this is you're going to have to do potentially a lot of manual searching because your parametric search over here. Even if you go to the manufacturer parametric search, you still are not going to like. There's going to be nothing in here that tells you okay, what? What is the reference voltage and what formula is used And you know, like there's nothing like that.

You just have to basically go in there. So if you know it's a buck for example, you can then apply filter. Let's just assume it's a buck that's going down to a lower voltage, which you know you might expect because um, you know this huge chip here, right? Probably needs some low core voltage or something like that. and maybe that's what this is, uh, doing here.

it's taken. I don't know. does this input come here or something like that here? I don't know when it's pairing something. I you know it's almost certainly going to be in a buck converter.

especially in automotive. Which, you know you're talking 12 volt. uh. system.

Like, practically everything's lower than that, right? So yeah, so you'd be pretty safe in actually selecting buck converters. Um, so we're in switching. It's definitely a switching converter. So what you want now is to choose a variable output one.

So here the output voltage. Okay, you don't want? Well, you will choose adjustable. Well, we'll choose all of these right because these are actually adjustable. Not that one there.

But so those have a range and adjustable has its own range. Okay, so we're now down to 183. No 69 results remaining. Okay, so there you go.

These are all of the Uh Sot 23 5 switching voltage regulators, adjustable switching voltage regulators. Whoa. Some of them go up to two amps. Really? Oh geez, that's a beast.

Tlv 62569 Um, two amp high efficiency, step down butt converter in a soft 23. go figure. But yeah, that's like the only part looks like there's no equivalent to that. And of course we could go to somewhere like, um, Lcsc.

Uh, if you want to get like asian uh, source parts as well. Anyway, from Mouser, it looks like, uh, we've only got these manufacturers here. Is this new? I haven't seen this before. Most popular.

That's interesting. We looked at the analog devices, one, didn't We 3671, No. 3564. Okay, so open that one and then Lt 3406.

We'll get that one out there. It's unlikely because this is automotive unlikely to be some obscure, like, um, Asian brand one. Although you know, like if I don't know, it could be a Japanese car or something like that. So you know it could be a South Korean car you know, could pass from South Korea.

Who knows the 2830s? I know those. Uh, that's you know. Well, to me, that's like fairly common. There's a weirdo Lmr one.

Anyway, let's go in and have a look at these. So 2.25 megahertz synchronous step down converter. Nope. Incorrect Package 3406.

Okay, so 3406 looks good, so we'll get rid of that one. This is a possibility. The Uh 2830? Yeah, that requires external diode here. So um, I, we didn't see that in there, did we? No, there's no like external, uh diode there at all.

So nope. Anyway, incorrect package. That Lmr one also diode based and it's not going to be the correct package and also, I forgot, uh to do the Vn requirement as well. We probably should have done that.

assuming that it is actually 12 volts in, it may not be. It may be like there may be another converter on there, and it may be converting five volts down to a call logic level like, you know, 1.8 or something. So it's definitely not that. Nope.

And it's definitely not that one. So there's another, uh, weirdo footprint. So yeah, we can rule those out. so we're looking at, uh, really, the Ltc 3406.

Once again, it's not going to Murphy says it's not going to be one of those parts, right? But hey, we're looking for the pin equivalent part so that you can start down that journey of trying to find an equivalent. So really, we're back to, um, basically this Max Linear Joby here, and um, this Ltc jobby. So they're pretty much, um, it, Are they the same uh formula? see now the remember the one we looked at uh, before the Ltc 3406 B? Well, we found it again. But it's the Ltc 3406 A B and the A B is the adjustable version, whereas just the B version is non-adjustable So we'll get rid of that joby.

And it's the A B one here. So let's see if it's uh, same formula. And yep, sure enough, it is the same formula here. 0.6 volts times.

So these two, um, let's 1.5 megahertz, right? it? Basically, you know, as a rule of thumb use, go by the threat: 1.5 meg right? 600 milliamps, 800 milliamps for the max Linear. I'd say these are pretty equivalent parts. so if it was one of these, you could actually substitute uh with the other. Like, of course, you go into the details, look at the formulas and stuff like that.

but you know, these two look to be fairly. they're pin equivalent parts. They got the same, uh, setting, uh for the output voltage, so you can just whack it in. And you know, pretty much Bob's your uncle, but you would have to be careful with uh stability as well.

Like having the correct uh esr and your output capacitors and stuff like that. Some Uh circuits can get the heebie-jeebies Um, without the correct um output capacitors, so you want to look at detail in the data sheet for that. So there you go. I think we're done.

Um, I'm going to say an Sp 6 9 from Max Linear or an Ltc 3406 from Linear technology, but once again, like, these are only limited input voltage, right? So they're not going to be powered directly from 12 volts if that's the case. Um, then I don't know. It might be a special snowflake part, uh, or something that has a wider input voltage range because these are only like most of these. In fact, you probably find that, uh, all of them.

If we go back to our parametric search, they might all be oh no. Look, there's one 17-volt jobby here. Oh, it's that. uh, didn't we have a look at that uh Ti part there.

I don't think that that wasn't the correct pin out, was it? Oh, it's got Advanced Eco Mode trademark. There you go. Actually, this one looks like we've found another one which might do the business as well. Vsense.

That's correct. Uh p Why do they call it Ph? The switch node? Um Ph. But anyway, that's the correct. pin out.

So there you go. I jumped the gun there. We actually found we didn't go deep enough. We found three here, and one of them is certainly capable of direct 12 volt input for automotive use.

So yeah, functional block diagram for those playing along at home. Aha, the equation is somewhat different here, but it's um, it calculates R2 given a known r1, but you can rearrange that and anyway, it's 0.8 Um, it's not that 0.6 So um, yeah, this wouldn't be a direct substitution. With both of these. the formula doesn't work out.

I just noticed trending in Australia. buff head. good stuff. So anyway, I hope I've at least um, started down the journey of identifying this part here for Puria Solutions.

And I would start by looking at those three. um, trying to like he might already know what what the actual input voltage to this thing is and what the output voltage is supposed to be. If you know that, that helps a lot. but look at the resistor values, look at the formulas in the data sheets and you're on your way.

But um, yeah, it could take you know a significant amount of time to actually figure out what in this exact part is. But as I said before, please leave it in the comments down below. If you uh, have any idea exactly what this uh part is, and you know somebody in the comments, you know I've got a lot of viewers. Um, it's certain, probably someone's used it and go, oh yeah, I know that and the max linear one.

I don't think we ever found the F mark in can we do marking? No, no, it's not there, but it's unlikely to be any of these. um, but certainly not these two because the mark is not correct. But anyway, and hopefully it gives him something to go on and hopefully you enjoyed that and found it useful. If you did, please give it a big a thumbs up.

As always, discuss down below and if you want to ask me questions like this, Twitter's the place to do it. Catch you next time.