BQ25618E

The BQ25618E/619E integrates charge and voltage protection in a single device. It offers low termination current for switching chargers to charge wearable devices to full battery capacity. The BQ25618E/BQ25619E low quiescent current reduces battery leakage down to 7µA in Ship Mode, which conserves battery energy to extend the shelf life for the device. The BQ25619E is in a 4mm x 4mm QFN package for easy layout. The BQ25618E is in a 2.0mm x 2.4mm WCSP package for space-limited designs.

The BQ25618E/619E is a highly integrated 1.5A switch-mode battery charge management and system power path management device for Li-ion and Li-polymer battery. It features fast charging with high input voltage support for a wide range of applications including earbuds (True Wireless or TWS), earphone charging case, and wearables. Its low impedance power path optimizes switch-mode operation efficiency, reduces battery charging time, and extends battery run time during discharging phase. Its input voltage and current regulation, low termination current,and battery remote sensing deliver maximum charging power to the battery. The solution is highly integrated with input reverse-blocking FET (RBFET, Q1), high-side switching FET (HSFET, Q2), low-side switching FET (LSFET, Q3), and battery FET (BATFET, Q4) between system and battery. It also integrates the bootstrap diode for the high-side gate drive for simplified system design. The I2C serial interface with charging and system settings makes the device a truly flexible solution.

The device supports a wide range of input sources, including standard USB host port, USB charging port, USB compliant high voltage adapter and wireless power. It is compliant with USB 2.0 and USB 3.0 power spec with input current and voltage regulation. The device takes the result from the detection circuit in the system, such as USB PHY device.

The power path management regulates the system slightly above battery voltage but does not drop below 3.5V minimum system voltage (programmable) with adapter applied. With this feature, the system maintains operation even when the battery is completely depleted or removed. When the input current limit or voltage limit is reached, the power path management automatically reduces the charge current. As the system load continues to increase, the battery starts to discharge the battery until the system power requirement is met. This supplement mode prevents overloading the input source.

The device initiates and completes a charging cycle without software control. It senses the battery voltage and charges the battery in three phases: pre-conditioning, constant current and constant voltage. At the end of the charging cycle, the charger automatically terminates when the charge current is below a preset limit and the battery voltage is higher than the recharge threshold. If the fully charged battery falls below the recharge threshold, the charger automatically starts another charging cycle.

The charger provides various safety features for battery charging and system operations, including battery negative temperature coefficient thermistor monitoring, charging safety timer and overvoltage and over-current protections. Thermal regulation reduces charge current when the junction temperature exceeds 110°C. The status register reports the charging status and any fault conditions. With I2C, the VBUS_GD bit indicates if a good power source is present, and the INT output immediately notifies host when a fault occurs.

The device also provides the QON pin for BATFET enable and reset control to exit low power ship mode or full system reset function.

The BQ25619E device is available in a 24-pin, 4mm × 4mm x 0.75mm thin WQFN package. The BQ25618E is available in a 30-ball, 2.0mm x 2.4mm WCSP package.