 Hi, I'm M.P.I. Hi, I'm M.P.I. brought to you by Digi-Key, and everything you did, Digi-Key. This week it is from Texas Instruments Lady, and what is the new product of the week this week? Okay, this week's new product will get you on track. It is the BQ-27427, oh that's a mouthful, it's a new impedance track battery charge monitor for lithium-ion, lithium-polymer batteries. This one is kind of nice, it's a system side, so if you're using it with any battery, it does not go into the battery pack, it goes into the thing that the battery plugs into. It makes it perfect for products where you have these batteries that just plug in directly and you want to monitor their charge state. Now the nice thing about it, it has an integrated sensor resistor, we'll chat about that, and it has the impedance track algorithm going on inside, which does a really good job, a better job of keeping track of the battery charge state percentage, whether it needs to be charged, how many, you know, how old it is, how many times it has been charged back and forth, because that does affect how much current you can draw from it, and it's I squared C, so it's really easy to integrate, and there's a separate data sheet with all the registers and information, and you can also tweak the algorithm by classifying the battery using the TI BQ studio, so let's get right into it. Lithium polymer battery, the lithium polymer battery is very common for people designing portable battery powered recharge products, you know it, you love it, some cool things about it, they're very high density, they're easy to get in almost any size, they're very inexpensive, they have a nice high nominal voltage 3.7 volts, which means, you know, you can often use a linear or buck converter to power your 3.3 volt electronics off of it, put some protection circuitry in it, and you know, it's a pretty safe choice. One thing that's a little annoying about them though is it can be hard to know what the battery life is, and a lot of, you know, times when you're using a product, you need to know what percentage of the battery life is, is it like 2%, 10%, 25%, 30%, 90%, 100%, because that's going to tell you how long you can use it before you need to recharge, and that can also change your use case, like with my phone, says there's 10% less, I'm going to, you know, dim the back light, turn off the audio, stop streaming YouTube, because I want to keep the device going as long as possible, so that information is very useful. The thing about lithium-ion batteries is, if you go back one, so it's printed on it, the nominal voltage 3.7 volts, and the nominal storage, 1200 milliamp hours, but that nominal voltage 3.7 volts is just kind of like a rough number, depending on, in this case, your discharge rate, this is from a TI white paper, which can be linked in the text, how much current you draw from it is going to affect what the voltage is, because there is this built-in impedance inside the battery to the higher the current that there's going to be a little bit of a voltage drop, so if you draw as little as a couple hundred milliamps, you know, you're going to start at about 4.1, 4.2 volts, and then you're going to sit kind of in that 3.7, 3.8 to 3.6 volt range for like 90 percent battery life, and then it gets near to the end, and then it kind of plummets very quickly down to about 3.0 volts, but if you're drawing three amps or one and a half amps, you'll see that there's a depression to the voltage, which makes a purely voltage-based monitor hard to use, because if you don't know how much current is going through, you don't know which curve you're on, and so, you know, if you're reading 3.5 volts, that could mean that if you're drawing a couple of amps, you're still at 90 percent, but if you're drawing only 300 milliamps, it means you're at 5, 10 percent, so knowing how much current you're drawing is going to affect which curve you're going to follow to determine the current battery life. Likewise, another thing people know about lithium-ion and lithium-polyl batteries is that they are affected by temperature, such in cold weather, the voltage is going to droop as well. At normal, you know, 20 degrees C, you'll see kind of the standard 4.0 to 3.0 voltage over the life cycle of the battery, but if you are at negative 10 C, because you're in Fargo, then you're going to start at 3.4 volts before drooping down to 3 volts very quickly. So, you know, what curve you're on, current, draw, ambient temperature range is going to affect it. Another reason why, just measuring the open voltage of the battery or the loaded voltage of the battery is not going to necessarily tell you where you are in the battery life. So, also, thirdly, aging. As batteries get older, the voltage drops and the impedance goes up. That can affect, based on the current draw, how much voltage you're going to see there as well. So, you know, these three things are important to track how many times you've charged it, what rate you're charging at or discharging at, and the ambient temperature. And that's where impedance track comes in. So, impedance track is the trademark algorithm from TI that uses the current cool of counting, which is basically counting the current going in and going out, as well as, you know, calculating the impedance looking at the voltage to figure out what is the state of the battery, what percentage of capacity, as well as, you know, how long it's going to take to charge up, whether it's charging or discharging, everything you need to know about your batteries that you don't have to do the work, especially if you're using a device with, you know, not a lot of my controller cycles to spare. You can outsource that all to this very low quiescent current chip. It'll keep track of all the spore you and you don't have to try to, you know, measure the current going through a sensor system to determine how much current is leaving or entering your battery. There's a lot of details about impedance track. I'm not going to read this, but you can pause the video and look at it. But you know, this is an algorithm that happens inside. You do want to have some details about the battery pack, like you'll need to know, of course, what is the nominal peak voltages at a 4.2, 4.1, 4.3 volt battery, that depends on the chemistry with the battery pack sizes. And also, it depends on, you know, the manufacturer, the quality of the battery, you might have lower higher impedance. Also, the protection circuit is going to affect that as well. All this, you can program into the impedance track calculator by writing some couple of registers, and you'll get more accurate results. The benefits we chatted about, you know, basically does it all for you with the tradeoff of that you have a sensor system. And normally the sensor system is external, you'd have, you know, the component to add as well as, you know, any pull ups or pull downs, capacitors or so. And what's really nice is how simple this chip is to use. So it's, I didn't put the footprint here, but it is a nine pin BGA, I think it's like 1.6 by 1.6 millimeters. It's quite small. But even though it's a BGA, the center pad is shared with an outer pad, they're both ground. It's kind of nice. It means that you don't have to use a bugged via or like we're routing to try to get that center pad out. So you can kind of think of it as a eight pin BGA not a nine pin just, you know, short the center pin out to the ground. You've got iSport C, SEL, SDA, so you use that to communicate with the Mac controller. There is the integrated sensor system you see on the right. And then the output V-SYS, that is, you know, you plug in the battery to bat VDD and VSS you see in the bottom there, that's just the internal LDO. So you have to put a capacitor there, you have the battery voltage coming in goes to the sensor system and then out to V-SYS. So this goes in between the battery and your system voltage because it has that integrated sensor system on the high side. The cool encounter is used to calculate the impedance track algorithm. And then there's two more out IO. There's the GP out there's a general purpose output. You can use that as like an interrupt, it tells you when the battery voltages load past the threshold that you've programmed in. And there's also be in which can be used as a thermistor input, or it can be used if you have an external thermistor inside the battery pack for internal battery pack monitoring. There's also the possibility of using it as a switch input. So you know when the battery has been cycled that way you can reset the algorithm because otherwise, you know, the cool encounter is going to go out of sync. If somebody's replaced the battery on your device, you want to kind of start over and say, okay, we have a new fresh battery. We don't know how many times it's been cycled. We don't know what charge state it's at. So kind of resets the internal algorithm. As you mentioned, you will have to when you boot up this chip, you want to tell it what it's connected to to the best of your ability. So there's a couple of things like the chemistry ID and the battery pack size and you program that over I squared C, but you know, and they give you a list of the commands. There's also the ability to create a golden image, which is if you have, you know, a battery from your lot of batteries, especially this is if it's not being removed and replaced with some, you know, off, you know, an off the shelf battery, if it's like something in a well known battery, you can do a learning cycle where you have a deadboard from TI, you plug your battery in and it kind of does this charge discharge, relax cycle and it calculates some of some of the details about the battery and how it responds to charging and discharging that you can then enter into your I squared C programming. And this is gauge studio. So you use their about kit, you plug in the battery and it runs it for you. You know, if you're if you're doing a large run of a product and you want to get like really good, accurate, precise battery statistics data, I recommend it. If not, you can probably get away with just putting in the voltage and the current. This is an example of how you use the I squared C commands to program in the chip. Note that it does not have a problem. You know, it's a low cost chip here. So it's all in RAM. So when you turn on the mic control, you're gonna have to program it every time. So yeah, that's a trade off of very low cost chip. It's like 70 cents in quantity. You do have to program it each time, but it's not a big deal. You have like this key you have to insert and you put in the capacity and the voltage and all that do every time and you're good to go. It's not in stock, but it will be in stock soon. It wasn't stuck when I first picked this, but it looks like it's going to be in stock in a couple months. They sold out pretty quickly. It's, it's a nice little chip. I mean, it's very small. It's has integrated sensor resistors. It's like one less thing you need. You only need two passes connected over I squared C and for under like 70 cents, you can have a really high quality battery monitor for your product probably went off of battery. You want to know exactly what the state of charge is. That's me. That is this week's iron MPI