 The great search bar to buy the cheeky and eat a fruit every single weekly data user power of engineer and help you Yes, you find the things you want on did you key calm lady? You know, what is this? Great search. Okay, so I'm working on this board. That's going to interface with floppy disk drives like this one or like this Apple to disk to and These are Devices that need a lot of power. They need five and twelve volts And they need them at a couple amps apiece because they're driving motors spinning them around very fast and You need to have a good clean power supply. That's five volts and 12 volts and You know Historically, you could get these power adapters that would give you both five and 12 and they would actually plug in even directly into the Disk drive itself, but those are they're actually kind of expensive And they're very specialized And so I thought in this design for this board that's going to interface with disk drives Apple to you or floppy or whatever that instead of trying to like get this custom source five plus 12 volt Power adapter what I would do is say you just provide me Five volts. Sorry 12 volts at three or four amps You can get 12 volts three or four amp power adapters or usbc Can provide 12 volts at three amps as well and I'll give you the three I'll give you the three two to three amp five volt output as well as at 12 volts and then you know, you're good to go You don't have to have a good dual supply. I'll generate the five from the 12 So let's go to the computer and I'll I'll show This isn't the final design, but I wanted to sort of draft it out So you'd have um your 2.1 millimeter dc Jack and again, you can get 12 volts power supplies very easily I'll add an e-fuse here We'll cover that probably next week on the great search about how to do e-fusing because I want to make sure that people don't plug in More than 12 volts into here and accidentally, you know Put 12 volts into the motor because I don't want to have a buck converter also for 12 volts I'm I don't want to have a sepik. I don't want to spend the extra money When I'd rather have a fuse and just be like, hey, just make sure you use a 12 volt I won't let you use anything else and then I'll give you the five volt High current as well. So there's usb c but again usb c does not even, you know Yes, if you have a power delivery setup, you can kind of guarantee getting five volts at two or three amps But I'd rather just again generate it from this Chunky 12 volt power supply and use the usb just for communication to the computer and not try to use it for Um power input because again, you need a lot of current you need like two amps One amp, but let's say two to be safe um, and So normally, you know, if I'm trying to get um, you know five volts from a 12 volt power supply on something like You know a metro or something. I'll use like an az 1117 series. These are very very common. They'll give you about one um One amp one, you know point two five amps linear And uh, they come in your standard sot 223 or sot 89 They're very inexpensive. You can see they're about 10 cents a piece in quantity but And they come in fixed as well so I can get you know, I can Let's say I want a fixed five volt output Show you a couple options Yes, the az 5 10 cents a piece and they work great You know, you can get one amp out and the voltage drop is pretty minimal. I think it's yeah about 1.3 volts So definitely we'll get you current out of 12 volts. The problem is that the amount of heat we're dissipating out of this is Uh pretty high. So you're 12 minus 5 seven volt drop times, you know 1.2 amps Okay, eight watts. You're not going to easily dissipate eight watts from this little package You could do it with a to to 20 with a really big ass heat sink But you're definitely not going to be like this chip is not going to be happy It'll it'll give you five volts one amp maybe from like seven to nine volts. Okay, but not from 12 even though the um Voltage rating Can go up to 15 and that's something to watch out for like when I was like younger and I was starting out I was like, oh It says I can do 15. It'll give me five at one amp like it should work, right? But it Just because the the technical limits let you do it doesn't mean the thermal limits will match So for this kind of situation, this is where you would want a buck converter This is a perfect example of you want a high voltage convert to low and you and you can't dissipate that much power Also, it's a bit of a waste, right? I have to provide both five and 12 volts to you know a disc to power apple disc to floppy drive So I don't want to like Linearly lose two amps from my 12 volt power supply into the five volt regulator Even if I did have a gigantic heat sink because I still need two amps from the 12 volt as well So, you know, if I use a buck converter, I can draw 400 milliamps from the 12 volt. I just need a less power less big power supply So cost power everything savings the buck converters the way to go So, um, let's look at a DC DC buck converter And which got there's a lot of options So there's just fyi. Don't forget. They're switching controllers and switching regulators and switching Converter like there's there's like a lot of things that sound very very similar So these converters tend to be modules and there's nothing wrong with using modules Sometimes you're like, I don't want to go through like getting inductors and stuff You can get uh, you know, this chunky module from spark fun or you can get this You know plug-in style and there's nothing wrong with these. I'm like they can be very inexpensive However, you know, I want to keep it low cost Um, and I'm not the power requirements here are too high. So let's Do a regulator that will also regulate the output the controllers by the way, usually you need to connect up a separate Transistor and these are often used for extremely high current Or extremely high voltages where you need the transistor to be specced for some, you know, maybe 40 50 volts or whatever And you wouldn't get that with a regulator but 12 to 5 that's pretty common by the way like you're going to see There's thousands of options. So the regulator will give me a regulated output So many options 30 000 and a lot of them are in stock too. So let's look at only the active ones And let's look at the ones that are normally stocked and let's exclude the marketplace one So this gets us down to like a poultry 7 000 options Okay, and uh, you know, definitely there's there's tons and there's in stock. It's amazing It's a beautiful thing. So we want surface mount Because I'm going to pick and place it onto this board Um, I want it to be Definitely not negative. I want it to be positive. But sometimes my positive or negative whatever I'll just select all of these so all positive And then I want I only need one output Although, you know, it could be interesting. Um, if I did need a lot of current at three volts I could get a dual output that would give me 12 to 5 and 12 to 3 But I don't actually need that much current at three volts. I'm going to just toss an ldo on there To to convert the five volts to three volts because I only need like at the most 50 maybe 100 milliamps not worth getting another more complicated Buck setup going on. Okay, so let me apply I didn't even get rid of that many. There's so many options. Um, okay So the next Thing is do I want synchronous rectifier or not? So Normally I would say, you know, oh, I don't mind putting a diode in I'll show you the freewheeling diode I you know, I picked This old design that I had So like this design with the tps 5100 there is a freewheeling diode here Um, but you know, it's another component and these days are not Inexpensive they're, you know, 10 10 15 cents. So let's go with yes, let's do, you know, a synchronous rectifier um, why not Save one component also means usually there's a true disconnect Um between input and output usually, uh, at least it does with the boost converters Okay, and then I definitely want not boost. I want buck only so I'll select those okay There's really, you know, almost everything will do what I want voltage input the minimum Well, um, it's going to be 12 volt input. So let's make sure that I can handle um 12 volt or less and then Uh input maximum, let's make sure the maximum can be oops 14 volts or higher I don't know 150 cares Let's see if that okay now we're getting down to 2600 Um, let's look for only ones that are tape and reel Just, you know, if I'm I'm going to put this on the pick in place. I might as well get, you know, avoid the Did you reel and cut tape version or or uh tray versions? Okay And I think like that's pretty good voltage outputs Um They all kind of cover five volts. So, you know, I mean again, this is like one of the most common Um converters All right, so let's uh, let's look at the pricing quantity for a thousand pieces That likes to like to give me a sense and yet 2000 options. There's a lot of options. So you don't have to worry about that Oh, and then current output Forgot the most important thing um, so The motors on these They are usually specced for one amp, but um, you know, I want to make sure I have plenty of Space in my my power budget. So I'm gonna make the current outputs or the switch output be two amps or more because while this is Um, these floppy these floppies are one amp There could be older ones that are less efficient and they could spike up and maybe draw like two amps. So let's do two amps and up 50 amps is kind of We'll see. Okay. So now now we're doing good. Okay so lots of in stock options and one thing I noticed that there's a couple of You know popular winners here. There's the ap622 series From diode's ink and notice that buck computers are really inexpensive Like 13 cents 10 cents about the same price as the ldo, which is another thing It's like by the time you add the heat sinking to your linear regulator Um, because you have to get a separate heat sink. It could be the same price. It's just getting this is a synchronous box So all I need is the input capacitance output capacitance and a couple of inexpensive passives um to set the output voltage and um, you know An inductor but the inductors are usually, you know, maybe 10 10 15 cents. This is very inexpensive Um, and there's a lot of good options. There's three volt out. So I three amp out two amp out I did see like there's a lot of like There's the tps 562202 and then the tps 62207 and I was like, what's the difference between these two and um So I opened up the data sheets because I was like expecting this to this week And I was like, what is the difference between these two? So a lot of it is um the accuracy of the output feedback and also the frequency These are 580 and of course The lower the frequency the more efficient but the bigger the inductor So if you want a small inductor, you'll want higher frequency, but usually Get lower efficiency. So it's a kind of a trade-off, but um 600 kilohertz isn't too bad and also the Voltage range input and output. So this is 4.3 17 These are actually kind of very similar I don't even know what are the differences between the two And then yeah, I don't even know soft start Hiccup mode Non-latch I don't know the difference between the two these two pre-bias function. I don't know You can also check out on um ti. They seem like almost identical This is that thing. I wish they was a little bit more clear what the differences are between the two um But the second digit So there's five six, which is the tps five six, which is the series and then two Is two amp three is three amp. So at the same price, it goes to get a three amp version by the way um, there's also this the six 2201 You see the data sheet Yeah, so this output output range is 0.76 to seven volts And this is 0.8 to seven. So like there's this light. Yeah, all clearly they're all very very similar. They have the same um Fets inside and the same kind of configuration and pin out um But they have slightly different uh Pin numbers. I don't know some of them maybe have Different compensation on the inside All that looked pretty good though. Um I think I'm you know, I'm one of the people who I I definitely can be convinced by what the crowd is doing So I actually decided Of all these I think the diodes one is good, but I kind of like this one just because these two because both of these have um Like 100,000 and 20,000 in stock. So they're very promising You could also go to the power designer, which is what if you want like more specific component selection and what I put in here is the v in like 10 volts to 14 volts and the output five volts and then you know 1.5 amps and then uh, let's just say low cost And the ti uh web bench will generate It'll actually you you'll see the same part number show up, but it'll it'll calculate for you your inductors Um, the capacity that you want for you know ideal stability and the feedback. Um Resistors Thankfully, you don't have to compensate the design. So let this run In the mean in the meantime, it'll generate the designs, but I think that this one Is kind of what i'm going to go with the tps 56 2202 or 2201 and you can see here is the um My screen is very small, but you can see um, it generated Of this same family the 56 3 56 3 56 4 so goes up to 4 amps Um, it likes to I will say that the ti web bench looks to kind of give you a bigger than maybe necessary, uh power budget Um, but you can follow this and you can see like, you know entire bomb cost of like 51 cents It's a really good deal. These are also um higher frequency chips. It looks like the 56 2 2 is of the 202 But they're all good. I think this whole family will probably work quite nicely very simple very small And fairly good efficiency at v out five volts You know up to two amps about 92 which is about as good as you're going to get So, yeah, I think that this is what i'm going to go with the tps 56 2 2 series So i'm going to get this into my design and then next week We'll do the efuse for protection of this chip to make sure that you don't get more than about 12 14 volts coming in And that's a great search