The BQ25306 is a highly-integrated standalone switch-mode battery charger for single cell and dual cell Li-Ion, Li-polymer, and LiFePO4 batteries. The BQ25306 supports a 4.0-V to 17-V input voltage for fast charging. The devices sensorless topology enables high charge efficiency and low BOM cost. The devices best-in-class 1-uA low quiescent current conserves battery energy and maximizes the shelf time for portable devices. The BQ25306 is available in a 3x3 WQFN package for easy 2-layer layout and space limited applications.
The BQ25306 supports a 4-V to 17-V input to charge either single cell batteries or dual batteries in series with charge voltage from 3.4 V to 9.0 V programmable by resistor divider. The device features fast charging for portable devices. Its input voltage and current regulation delivers maximum charging power to the battery. The solution is highly integrated with an input reverse-blocking FET (RBFET, Q1), high-side switching FET (HSFET, Q2), and low-side switching FET (LSFET, Q3).
The BQ25306 features lossless current sensing to reduce power loss and BOM cost with minimized component count. It also integrates a bootstrap diode for the high-side gate drive and battery temperature monitor to simplify system design. The device initiates a charge and completes a charging cycle without host control. The BQ25306 charge voltage and charger current are set by external resistors. The BQ25306 charge voltage is programmed by an external resister divider and it charges the battery in three phases: pre-conditioning, constant current, and constant voltage. At the end of the charging cycle, the charger automatically terminates if the charge current is below the termination current threshold and the battery voltage is above the recharge threshold. When the battery voltage falls below the recharge threshold, the charger will automatically start another charging cycle. The charger provides various safety features for battery charging and system operations, including battery temperature monitoring based on negative temperature coefficient (NTC) thermistor, charge safety timer, input over voltage and over current protections, as well as battery over voltage protection. Pin open and short protection is also built in to protect the charge current setting pin or battery voltage feedback pin if accidently opened or shorted to GND. The thermal regulation regulates charge current to limit die temperature during high power operation or high ambient temperature conditions.
The STAT pin output reports charging status and fault conditions. The BQ25306 provides up to 3-A continuous charge current to a single cell (1S) battery or dual cell batteries in series (2S). When the input voltage is removed, the device automatically enters a low current HiZ mode with very low battery leakage current to the charger device. The BQ25306 is available in a 3 mm x 3 mm thin WQFN package.