 The Great Search brought to you by Digikey and Adrian. Thank you, Digikey. Lydia, to use their powers of searching and finding, especially in the middle of this drought, this chip drought, to show you how to find what you're looking for. Lydia, what is The Great Search this week? Okay, The Great Search is actually what I did today. So, because some Sundays I'm like, what am I gonna do with The Great Search? And then today I was like, oh man, I gotta find an alternative for this part that I can't get, that I can't get, and the alternatives I can't get. And before you know it, you're like four layers down. That sounds exactly like Great Search. That's The Great Search, that's where we're at. So, for this design, this design for this feather, I used the LC7909203 battered monitor chip. The TDFN version is no longer available. It went to end of line. There was no last time buy because of silicon shortage. And so I kind of got like the rug pulled out under me. That's a good idiom, rug pulled out under you. We're collecting idioms. And stuck without an alternative. And there is the, you know, we covered, okay, we can always get alternative packages sometimes. And there is an alternative package for this chip. The BGA package, and I can use that BGA package, you know, temporarily basically for a few months, but it will also run out, it's end of line. So I want to find an alternative lithium ion single cell battery monitor, something that has an ADC, communicates over I2C and doesn't use a lot of power so that, you know, it can stick this on. It has the, you know, it does the battery monitoring, Coulomb counting, state of charge, calculations for you, while still letting the main processor go into deep sleep. And when it wakes up, it can always ask the chip what's the state. And of course, I want it to be inexpensive. I want it to be easy to use. And I want it to be a package that I can put on a two layer board. So I thought that's what we would do. All right, let's do it. Okay, so let's go to the computer. Okay, so this is the previous package, the chip that I was going to use, the TDFN chip. And then, you know, I can swap that for the BGA package. And this will, again, I can kind of limp along with this for a few months because I can get some of these, but eventually those will run out. And this is the life we're living. So the chip that I was using before was basically this one, you know, this is no longer manufactured. It says some substitutes, you know, it has some substitutes, but we're gonna do our great search substitution work. So what I want is a battery monitor. I want to do one lithium ion thing, I squared C and surface mount. Although, you know, they're all gonna be surface mount. And let's see what we've got for similar devices. I'm not gonna say normally stocking or in stocking, I'm gonna say no marketplace, just because it's a little confusing. I want to just, I'm kind of in the specification stage, so it's like I don't really care whether it's in stock right now, as long as I can get it in a few months. And I want to look at prices in the, you know, 5,000 piece range or so. And, you know, as you can see there, this is the chip that I historically liked, you know, these are the two versions. They're the least expensive at about 70 cents a piece. The BGA version and the LC709 TDFN version. But, you know, this one not available. This one I can use until they run out of stock. So let's go down the list. Ooh, the BQ27426. Okay, this looks pretty good. Is that the one? What? Is that the one? No. Well, no, not only is it not in stock, but if I ask it, when's it gonna be in stock? It says April 2022. Okay, so it's not only are we trying to find a part, but I'm like, I really want a part I can get, you know, like this year, maybe, you know, would that be so hard? Maybe get it in the next like three months. We were spoiled when we were, when we were babies buying parts that were in stock. This family's, you know, it is quite a nice family of chips, but yeah, basically, you know, all of them are April 2022. This is the same part of that family. This one I think is also, you know, September 2022, like not even within the next year. I'm gonna be able to get this part. So I basically kind of went down this entire list. And until I, and then this one was okay, but I really didn't want a BGA. Again, I want something that's a two layer board. I don't want something that's BGA with middle pads because I really don't want something that's gonna be a pain to route. So what I did find, you know, I basically like scanned through this. Almost all of these are completely unavailable anytime soon, except for this one, the Mac 17 048. And this one not only has 3000 in stock, but it has 9000 in the factory. It's not expensive, but it is TDFN. I can get it, you know, quickly. Another thing you can do is of course, you can put down, you know, even more. And you can see like, well, there's gonna, you know, if I need 30,000, I'm not gonna get them till 2022, but there are gonna be two more shipments of 10,000 a piece, so in October. So, you know, I, if this is something I want to book for nearby delivery, you know, I have a shop, but again, it isn't stock. I'm not gonna need more than 10,000. I just kind of know that that's 10,000 a year is about how many, you know, that's how many I'm gonna need for now. So I think that, you know, this is kind of what I'm thinking of going with. So I designed a, I did a, you know, a board package for it and laid out the package. And then I designed a breakout for it. So, you know, this is what I start with whenever I want to design. I basically pulled out the LC79203 and I put this in. One nice thing about this chip is it doesn't have the, some of the BQ chips, the TI chips used Coulomb counting when they had the basically resistor between the input and output. And one thing that is kind of nice about this Mac17 chip is like the OnSemi LC709203, it doesn't have a resistor. It actually looks at the voltage, the historical measurement of the voltage to track what the state of charge is. And, you know, I kind of like that. I think it's nice because it doesn't matter, you know, especially for a breakout board where people can accidentally connect the wrong way. This is a kind of an elegant method of measuring because you don't have to worry about having it backwards and you don't have to worry about the resistance, you know, being in the way of your boost converter or something or affecting something down the line. So I'm gonna start with this. I normally actually would have gone for the BQ chips. The BQ chips were quite nice. They were much less expensive and they had I squared C and they had, you know, also either voltage or built-in Coulomb counting capability. But if I can't get it in the next, you know, six to 12 months even, if that's as soon as I can get it, I'm gonna start actually designing with parts that are more expensive just so I can get something out the door and then reevaluate in a year. It's easy to then, you know, I can always reduce the cost later by subbing out the old part, but not being able to ship something costs money every single day. So yeah, these are the design trade-offs I'm currently making is going with parts I normally wouldn't go with just because I can get them, knowing that I'll probably have to do a redesign down the line, but you know, I'll deal with that later. You know, I'll say, hey, I redesigned this for a cheaper chip and here is a new driver and here's the differences. And I've done that before. We've designed a lot of our feather boards or early Metro boards, whatever, with FTDI chips. And then when we could get Silabs USB serial converters, which I like a little bit more than the FTDI ones, they're less expensive and they have a couple of capabilities that I like. Very high speed, you know, data transfer and stuff. I redesigned a lot of boards and said, okay, I used to use the FTDI chip now using the Silabs chip. Well, the Silabs chip is also, I end of line, so maybe we'll do a future show where I show how to swap out a Silabs 2104 as well. Yay, it's like juggling. All right. And that's the great search.