This week’s EYE on NPI (video) 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 is now 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.
Let’s look at some specifications:
- High power density, high integration buck-boost charger for 1-4 cell batteries supporting any USB PD 3.0 profile
- Integrates four switching MOSFETs, BATFET
- Integrates input and charging current sensing
- Highly efficient
- 750-kHz or 1.5-MHz switching frequencies
- 5-A charging current with 10-mA resolution
- 96.5% efficient: 16-V battery at 3A from 20V
- Supports a wide range of input sources
- 3.6-V to 24-V wide input operating voltage range with 30-V absolute maximum rating
- Maximum power tracking with input voltage dynamic power management (VINDPM) up to 22 V and input current dynamic power management (IINDPM) up to 3.3 A
- Detects USB BC1.2, SDP, CDP, DCP, HVDCP and non-standard adapters
- Dual-input power mux controller (optional)
- Narrow voltage DC (NVDC) power path management
- Powers USB port from battery (USB OTG)
- 2.8-V to 22-V OTG output voltage with 10-mV resolution to support USB-PD programmable power supply
- OTG output current regulation up to 3.32 A with 40-mA resolution
- Flexible autonomous and I2C mode for optimal system performance
- Integrated 16-bit ADC for voltage, current, and temperature monitoring
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 are 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.
OK we’ve done the output, we’ve done the input. Now let’s 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.
Although this chip can run fully stand-alone, thanks to the resistor-set PROG/ILIM pins, it also has a fully-featured I2C port with registers that can turn anything on/off or configure inputs/outputs. There’s also an ADC to monitor any voltage or current, for tracking efficiency or managing battery-life.
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.
See this at Digi-Key at https://www.digikey.com/short/3q2mnt5t