The BQ25306 is a highly-integrated standalone switch-mode batterycharger for single cell and dual cellLi-Ion, Li-polymer, andLiFePO4 batteries. The BQ25306 supports a4.0-V to 17-V input voltagefor fast charging. The devices sensorless topology enables high charge efficiency and low BOMcost. The devices best-in-class 1-uA low quiescent current conserves battery energy and maximizesthe shelf time for portable devices. The BQ25306 is available in a 3x3 WQFNpackage 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 ordual batteries in series with charge voltage from 3.4 V to 9.0 V programmable by resistordivider. The device features fast charging for portable devices. Its input voltage andcurrent regulation delivers maximum charging power to the battery. The solution is highlyintegrated with an input reverse-blocking FET (RBFET, Q1), high-side switching FET (HSFET, Q2), andlow-side switching FET (LSFET, Q3).
The BQ25306 features lossless current sensing to reduce power lossand BOM cost with minimized component count. It also integrates a bootstrap diode for the high-sidegate drive and battery temperature monitor to simplify system design. The device initiates a chargeand completes a charging cycle without host control. The BQ25306 chargevoltage and charger current are set by external resistors. The BQ25306 charge voltage is programmed by an externalresister 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 terminatesif the charge current is below the termination current threshold and the battery voltage is abovethe recharge threshold. When the battery voltage falls below the recharge threshold, the chargerwill automatically start another charging cycle. The charger provides various safety features forbattery charging and system operations, including battery temperature monitoring based on negativetemperature coefficient (NTC) thermistor, charge safety timer, input over voltage and over currentprotections, as well as battery over voltage protection. Pin open and short protection is alsobuilt in to protect the charge current setting pin or batteryvoltage feedback pin if accidently opened or shorted to GND. The thermal regulationregulates charge current to limit die temperature during high power operation or high ambienttemperature conditions.
The STAT pin output reports charging status and fault conditions. TheBQ25306 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 deviceautomatically enters a low current HiZ mode with very low battery leakage current to the chargerdevice. The BQ25306 is available in a 3 mm x 3 mm thin WQFN package.