EYE on NPI – TI BQ25792 I2C Controlled, 1-4 Cell, 5-A Buck-Boost Battery Charger @TXInstruments
Channel: Adafruit Industries
Date: 06/05/2021

This week's EYE on NPI is one I've personally got an EYE on for a few months: the TI BQ25792 I2C Controlled, 1-4 Cell, 5-A Buck-Boost Battery Charger. This luxurious charger caught my eye a few months ago and now it's available for purchase and I'm really excited about it. This chip does everything you could ever want from a battery charger. We showed off a charger chip last week that was designed specifically for ultra-low current and voltages - great for TEC's or small solar cells. But what if you want HUGE charging capabilities? The TI BQ25792 has you covered, no matter your application.

First great thing - support for any size battery. We have lots of battery packs in the Adafruit shop, and in particular we use 1S batteries - if there's more batteries they are wired in series. But there's lot of folks who are building robotics that require higher voltages, so they have 2S, 3S, or 4S batteries. This charger can handle any of em, and you can configure the battery pack size using a simple resistor on the PROG port.

Second great thing - support for just about any voltage power supply input. Once you set the battery size, the output charging voltage has to be 4.2V-per-cell. Normally that means that if you're charging a 1S battery, you'd want a 5V power supply (4.2V plus some headroom). For 2S you want 9V to 12V, etc. Sometimes you'll see buck or boost chargers that let you have a lower or higher voltage. This chip is a buck-boost so you can have anything from 3.6V to 25V input and it will do the right thing to get you the voltage you need to charge the battery pack you have. There's some efficiency-loss on conversion, but much less than a linear supply and you don't have to worry about needing the exact-right power adapter or USB power supply. (https://e2e.ti.com/blogs_/b/powerhouse/posts/universal-and-fast-charging-a-future-trend-for-battery-powered-applications)

OK we've done the output, we've done the input. Now lets look at the creamy middle:

This charger has our favorite TI-capability: VINDPM and IINDPM - the ability to track the input voltage to make sure it is not drooping from over-draw. Say you have a battery, you want to charge it at 2A, but the wall adapter maxes out at 1A - you don't want the voltage to collapse on you, it's better to charge slowly at 1A than not at all at 2A. VINDPM/IINDPM auto-monitors the voltage and if it starts dropping, it will reduce the current draw. There's also ICO, which attempts to find the max-power-point for the power adapter, which may not be the exact same thing since there's different buck-boost efficiencies at different voltages.

For when you're using USB for power, the charger can auto-detect the 'Apple-style' resistors used to set the max-draw current available. (In theory, we acknowledge it's probably better to just VINDPM/IINDPM when possible but we figure it's also polite to stick to the max-current-draw set by the chargers.

Finally, there is an "OTG" mode where the converter 'turns around' and can be a buck-boost that runs off the battery to charge another device. Really a wonderful chip with a lot of capabilities and looks like no matter what it is you're trying to charge or power! I'm ordering some BQ25792 today for a new design I'm working on. From the looks of this datasheet, TI really stepped it up here (pun intended!) to make a battery charger everyone will love.  Check out TI's video for a lot more details (https://www.youtube.com/watch?v=Wjk5YWrt8Ww)

The BQ25792 is stock right now, for immediate shipment from Digi-Key (https://www.digikey.com/en/products/detail/texas-instruments/BQ25792RQMR/13577777)

See on Digi-Key at https://www.digikey.com/short/3q2mnt5t