BQ25628

The BQ25628 and BQ25629 are highly-integrated 2A switch-mode battery charge management and system power path management devices for single cell Li-ion and Li-polymer batteries. The solution is highly integrated with built-in current sensing, loop compensation, 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. The device uses narrow VDC power path management, regulating the system slightly above the battery voltage without dropping below a configurable minimum system voltage. The low impedance power path optimizes switch-mode operation efficiency, reduces battery charging time, extends battery life during discharging phase, and the ultra-low 0.15µA ship mode current extends battery shelf life. The I2C serial interface with charging and system settings makes BQ25628 and BQ25629 truly flexible solutions.

The BQ25628 has the ILIM pin to set the default input current limit and TS_BIAS pin for controlled thermistor bias. The BQ25629 supports a wide range of input sources, including standard USB host port and USB charging port. The device is compliant with USB 2.0 and USB 3.0 power specifications for input current and voltage regulation and meets the USB On-the-Go (OTG) operation power rating specification up to 2.0A.

The power path management regulates the system slightly above battery voltage but does not drop below the programmable minimum system voltage. With this feature, the system maintains operation even when the battery is completely depleted or removed. When the input current limit or input 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 until the system power requirement is met. This supplement mode prevents overloading the input source.

The BQ25628 and BQ25629 power an accessory attached to PMID either directly from the adapter or from the battery in either boost or bypass OTG modes. Boost OTG provides a regulated voltage at PMID from the battery via boost operation in the converter. Bypass OTG provides a direct path from the battery to PMID for highest efficiency. The BQ25628 and BQ25629 may be configured to automatically transition into boost OTG mode when the adapter is removed, and back into forward charging when the adapter is attached in order to power PMID in either configuration without host intervention. In forward charging, boost OTG and bypass OTG, the PMID_GD signal indicates PMID voltage and current are within accepted ranges. PMID_GD may be used to drive an external PMOS FET to protect attached accessories by disconnecting them from PMID if an out-of-range voltage or current is detected.

The BQ25628 and BQ25629 initiate and complete a charging cycle without host control. By sensing the battery voltage, it charges the battery in four different phases: trickle charge, pre-charge, constant current (CC) charge and constant voltage (CV) charge. At the end of the charging cycle, the charger automatically terminates when the charge current is below a preset threshold and the battery voltage is higher than the recharge threshold. Termination is supported for all TS pin temperature zones.

The BQ25628 and BQ25629 provide various safety features for battery charging and system operations, including battery negative temperature coefficient thermistor monitoring, charging safety timer and overvoltage and overcurrent protections. The thermal regulation reduces charge current when the junction temperature exceeds the programmable threshold. The STAT output reports the charging status and any fault conditions. Other safety features include battery temperature sensing for charge mode and OTG boost mode, thermal shutdown and input UVLO and overvoltage protection. The INT output notifies the host when a fault occurs or status changes.

The BQ25628 and BQ25629 are available in a 18-pin, 2.5mm × 3.0mm WQFN package.