 the great search brought to you by Digikeynator. Thanks, Digikey. This is the time of the week where LadyAida uses her power of engineering to help you find the things you want to find on digikey.com. What are you looking for this week, LadyAida? Okay, so this week chip shortage is not quite ending. It's relaxing a little bit, but there's still a lot of parts that didn't make it to the other side. And one of those is the fan 5331. Now you might be saying, LadyAida, you covered the fan 5331 a couple months ago. I remember that you found an alternative for it. No, no, no. My friend, that was the fan 5333, which is the constant current version of this boost converter. I'm now going to be looking at the constant voltage output version of this boost converter. The boost converter before was what I used for LED backlights on four, seven, ten inch TFT displays. It's one, you know, big LED chains where you want to have a constant current of 20 milliamps through multiple chains of LEDs. The fan 5331 is what I use often times for e-ink and OLED and TFT displays where I need a bias voltage, especially for OLEDs. This is very common. You need to give it a 9, 12, 16 volt bias to activate the OLED even though it's not like the main power source. You do need, you know, 50 milliamps or so, maybe 20 to 50 milliamps available for all sorts of devices. As I just mentioned, sometimes audio circuitry also, you'll need plus 12 volts even if you're not using a full 12 volts for your audio signal. The rails need to be hired because you need a headroom for your audio amplifiers and they go up to maybe six volts. So again, you know, for biasing, this isn't a power. Well, that's not what I would call a power boost converter. Although if you only need 100 milliamps, then it'll do the job as well. So let's go to the computer and let's look at this chip. So the fan 5331, I really, really love this boost converter. 1.6 megahertz frequency, adjustable up to 20 volts and it has a built-in one amp peak current switch and it comes in a SOP 235. This thing is like, it was a bread and butter. Like I could toss it to any circuit. It was, you know, all about a buck or less. It did the job beautifully, perfectly. They never blew up. They were super stable, low shutdown current, low RDS on, lovely, lovely chip. So you're like, wow, why don't you just buy more from Digikey? That's a great question. If you were to find this part on Digikey, you would see it is last time buy. Last time buy means they will do one more run. And then, you know, if you need a couple of years worth, please put in a couple of years worth that you need to complete your manufacturing until you can change over to another part. I will do a last time buy because I, you know, I like to have some backup for, yeah, sometimes you find alternative and the alternative isn't quite perfect. You might as well put in that last time buy order. However, I've also learned sometimes last time buy means no, that's a, we actually are never going to send it to you. I'm looking at you STMP 811, who's last time by lasted two years, and then I never actually got the part. And then they told me they will never send it to me. So it does happen. Not say it's going to happen here, but I've learned when I see last time buy, I find alternative immediately. So a couple alternatives suggested, but actually, I wanted to, you know, some of these might be okay, but let's use our patented search ability to find something similar-ness. So we want a DC-DC regulator with internal switches and one output. I'm not as picky about the internal, you know, the Minimax input voltages, because again, it can be wider, it can be narrower, basically as long as it's three to five volts. I'll try to find something with about 20 volts, one amp switch, and hopefully high frequency. I do want it in SOT 23.5. I want it ideally to be pin compatible and functionally compatible, so I don't have to redesign. Okay. So, and then, you know, we're going to get pricing at 1,000 pieces. So this is fun. This is the, you know, this image is not correct, because this is SOT 23.5, but it's good to know. And there's a couple obsolete parts. Here's that fan 5331. So this is, you know, last time buy. And then a couple others in that family, you can see the fan 5333 is also last time buy. So let's, let's have a look at active, and that'll cut it down like half. So only 30 options now. I also want to look for normally stocking only, because as some of these are, you know, not, you're not available. I don't mind if it's marketplace, that's okay. One thing I'll note is a few of these are step down. They're not boost converters. Like this one, this is a regulator, and this is a regulator, and they're step down converters, not step up converters. So we do want to note that, you know, you want to make sure you pick both SEPIC style and step up. SEPIC is a single-ended, something-something converter. And basically, you know, it's usually a buck boost. Sometimes you can configure, you know, by adding more trends, yeah, more shocky diodes and more inductors, you can kind of reconfigure it. So it's okay for the voltage goes a little bit under or above. That's okay. We'll just select both. The voltage supply max is fine. The voltage supply min, all these are fine. They all cover three to five volts. That's fine. And the voltage outputs are, for these are also fine, because they just want at least 20 volts. The current output per channel, again, this is confusing because there's output and switch. Usually they're specced by the switch, I will say. So that said, if you look at the switch current, you're not going to get, you know, there is one that's 2.8 amps and it's like, wow, that's cool. But it's out of stock. It's the LM3410. Currently not in stock. So that's a little sad. Maybe I'll actually say only one will get in stock ones as well. Okay, so back here. So the current output channel, so, you know, basically there's 550 milliamps. That's kind of the max. So if that current output is important to me, the LM2704F, it's a little bit more expensive. It's $1.25 on tape and reel. But, you know, it does do the job. It's adjustable up to 20 volts. You know, built-in switches, half as much, 550 milliamps. Great for LCD bias supplies. What a coincidence. And then, you know, this is basically your classic circuit, which is the same circuit you'd use for the FEN 5331. And I did check the pinout. The pinout is identical. I can quickly look it up to verify for you. So it's switch, ground, feedback, shutdown, be in. And this is switch, ground, feedback, shutdown, be in. So one, two, three, four, five. It's in the same order and the same circuit. Although the feedback resistors may have to be adjusted, but that's not a big deal. But otherwise, this looks, you know, very similar. You have to give it the shocky diode and the inductor and does the rest. So this one's good. However, you know, for a lot of the bias circuits, I don't need necessarily 558 milliamps. I'm glad it's available. And then, of course, if I'm willing to spend even more, there is a version that has a built-in 2.8 amp switch. So that's good to know. And it's actually kind of nice. It's also 1.6 megahertz. Again, it's more expensive. The original FEN 5331 was about 75 cents. This is $1.50. But there is something available, the LM3410. So that's good to know. But for my purposes, I'm actually kind of OK with using, you know, 350 milliamp switch. So again, I only need like 10, maybe 20 milliamps at 9 to 12 volts. It's not huge. Again, it's not a power converter. It's a bias generator. So I'm actually OK with this one, the LM2703. Right? Because again, this comes in a family, the 2304, 2704, and then the 2705 all, you know, you pay more for the bigger switches. But this one does the job. And hey, it's in stock, hard to beat. But this will do the job quite well. Again, 2.2 to 7 volts in, up to 21 volts output. Simple boost converter. It'll do the job and then pin compatible. So I can just drop it in. And for almost all of my OLED biasing needs, this chip will work quite well. And that's a great search.