 Hi, I'm MPI. Hi, I'm MPI, brought to you by Digi-Key. Thank you, Digi-Key. And this week, it's Texas Instruments. Lady, what is the new product introduction of the week this week? Okay. This week, we are back with a classic TI. They make such cool stuff. And we're going to be looking at their T-Mux series of analog switches. They come in T-SOP, they also come in QFN, but this is the icon that's going on the Digi-Key site. So the T-Mux 821 series is SPST analog switches. They are a fully solid state, not the same as a relay or even a solid state relay. These are analog switches that are meant to pass analog signal back and forth, but they're much, much faster than realized on a mechanical situation. They don't click and they don't get oxidation. And they're definitely a lot smaller and less expensive than solid state relays. You saw that packages just like a 16 or 18 T-SOP goes on your board and it can switch bidirectionally signals that can go up to 100 volts, which is very high. This is a particularly high voltage analog switch. And then you can control the switch to open or close with your logic levels of way below 100 volts. It goes down to 1.8 volts. So let's take a look at what we've got here. So you are familiar with your standard push button switches. You want to connect analog signal back and forth. You can use a push button switch or a slide switch, toggle switch. Digi-Key has tons of those. If you don't mind having a mechanical connection, these work really great. You want to switch audio signals from headphone to speaker. And you don't mind having a button or a switch before it will do the job quite well. And there's like hundreds and hundreds of thousands of options as well. This is just the push button switches. But for toggles and slide switches, there's also a ton of options. But these are mechanical switches. And so somebody has to mechanically press the button or flip a switch. Like I said, you can use a relay, but relays are really, really big. And they're loud and clicky and they do fail after a while because they eventually oxidize. And so an analog switch is kind of like a mysterious and mystical thing. It acts just like your everyday normal mechanical switch, except that the thing that connector just connects is a signal, a digital signal. In this case, they are implemented by having two back-to-back and FET and PFETs. And by manufacturing this on your silicon and doing good job with the isolation and the specifications, you can have it be a bi-directional switch. So signal can go back and forth between the two sides. So it is interesting. Most people think of a FET switch, a PFET or NFET switch, as sort of a uni-directional, you want to connect a source voltage to a supply, sorry, a source voltage to a sinking load, you can do that with a switch. But in this case, you actually have true analog bi-directional communication. And in this case, it even goes at a much, it can go at a fairly high voltage, 100 volts of common mode between the two. One nice thing about having analog switches is you don't get switch bounce. So like I mentioned, relays are often used in such situations, but you have to see for telecom, but you will get chatter, you're going to get oxidation and they will fail eventually. Whereas what's nice about these analog switches is you don't have, you know, when they switch, they switch on pretty much instantaneously. So you can switch back and forth multiple times after wearing about oxidation or switch failure. But there are some downsides. So one downside is that when you're dealing with a mechanical switch, when it's closed versus open, it's basically either a short, like almost zero ohms, 0.001 ohms or so. And when it's open, it's infant ohms. There's like no connection between the two contacts. When you're dealing with a analog switch, there's always going to be some resistance. So when it's closed, it's not zero resistance or even 0.001. It's five ohms, which is like not a small amount. And in this case, it is also, I think it's like seven to 10 ohms. You can get very low RDS, sorry, R on analog switches. This one is medium. You know, I did compare this with the CD4066, a common low cost analog switch. And that was like 120 ohms. So this isn't too bad, five ohms or so. And when it's open, it's not truly, truly open. You do have some leakage between the two. In this case, it's 10 mega ohms, for example. You can find the specifications for the actual on and off resistances are in the datasheet. In this case, the on resistance is about five to 10 ohms, depending on the temperature. It is pretty consistent. Like you're not going to get a high variation with temperature, which is kind of nice. Some switches, make sure you check the spec sheet with temperature and voltage. The specified resistance on the front page of the datasheet may go up quite a bit. And then you can see the drain off leakage. That's how much current will leak between the A and B contacts. Another thing to watch out for with analog switches is you do have to, it seems obvious in, you know, hindsight. But if you have an mechanical switch, the voltage that you use to turn on off, say the relay does not relate to the voltage that you're switching. You know, you can turn on off the relay with three volts. And then when you're switching, sorry, the voltage you're using to turn on and off the relay can be like three to five volts. And the voltage it's switching can be up to like 220 volts AC. In this case, you do have to provide, with these analog solid state switches, a plus and minus voltage that covers the total voltage that you're applying to have on the A and B pins. So for example, you want to switch a voltage analog voltage that can go as high as, you know, plus minus 12 volts. You'll have to provide VDD with 12 volts and be assessed with negative 12 volts. So you'll have to cover that total voltage because you have to have your MOSFETs conduct. So watch out for that. Don't assume like, oh, my logic level is 1.8 volts. So I'm going to give it 1.8 volts for the VDD. Now it has to be as high as the highest voltage you're planning to put through the analog switch. Okay, next up, they are not isolated. Seems kind of obvious, but you know, compared again to relays or switches where you have some physical space or plastic between you and voltage, that's not going to happen here. It's all on one chip. So you could get a separate digital isolator. You know, I just quickly looked up on ti.com and this came up. There's silicon and opto isolating either will work just great. But there are some nice things that are, you know, like I wanted to give you the downsides of like, hey, watch out for these things. I have definitely been bit by some of them. But some of the good things are, I like little details like they have the built in pull down resistors were automatically enabled or disabled by default. There's a nice failsafe so that if you apply voltage to the selection pins, and for some reason the voltages aren't on the power pins, you won't blow up your chip. I have absolutely done that. So kind of nice to see that. There's also a design for latch up immunity, which is going to be very handy. You do not want your switches to latch. Like I said, the pull down resistors are built in and you can run them off a very low logic. Sometimes the logic used to switch has to be similar to the voltages that are the highest and lowest VDD and VSS. In this case, you can use your normal mic controller voltage, but you can also go up to 48 volts. So if you are using the microcontroller, if you're using some signal coming in from your project, you might be able to use the working voltage if it's like 24 or 48 volts. There's three variations, the 80 to 11, 80 to 12, 80 to 13. The only difference, the pinouts are the same. The only difference is whether they're normally connected, normally open, or alternating, normally open and normally connected. In stock right now, all three versions. So, and lots of them in stock too, which is kind of nice. Sometimes I'm like, no, there's only two and they sell out. But in this case, very handy, really useful often for audio, video. I don't know if this would be necessarily good for USB. You should check whether the high speed rating would be useful for it, but definitely AV switching analog switches or test equipment. You want to connect different voltages around. Not good for switching big power supplies, but I think you do about 200 milliamps. And that's this week's IMPI.