BQ25308

The BQ25308 is a highly-integrated standalone switch-mode battery charger for 1-cell Li-ion, Li-polymer, and LiFePO4 batteries. The BQ25308 supports 4.1V to 17V input voltage and 3A fast charge current. The integrated current sensing topology of the device enables high charge efficiency and low BOM cost. The best-in-class 200nA low quiescent current of the device conserves battery energy and maximizes the shelf time for portable devices. The BQ25308 is available in a 3x3 WQFN package for easy 2-layer layout and space limited applications.

The BQ25308 supports a 4.1V to 17V input to charge single cell batteries. The BQ25308 provides up to 3A continuous charge current to a single cell 1S battery. The device features fast charging for portable devices. Its input voltage regulation delivers maximum charging power to the battery from the input source. 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 device also provides a safety feature that completely inhibits charging of a dead battery.

The BQ25308 features lossless integrated 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 and completes a charging cycle without host control. The BQ25308 charge voltage and charge current are set by external resistors. The BQ25308 detects the charge voltage setting at startup and charges the battery in four phases: battery short, 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 against the charge current setting pin ICHG accidently open or short 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. When the input voltage is removed, the device automatically enters HiZ mode with very low leakage current from battery to the charger device. The BQ25308 is available in a 3mm x 3mm thin WQFN package.