BQ25620

The BQ25620 and BQ25622 are highly-integrated 3.5A 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 devices use 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 the BQ25620 and BQ25622 truly flexible solutions.

The BQ25620 supports a wide range of input sources, including standard USB host port, USB charging port, and USB compliant high voltage adapter. It sets the default input current limit based on the built-in D+/D- USB adapter detection interface. BQ25622 has an ILIM pin to set the default input current limit and a TS_BIAS pin for controlled thermistor bias. The device is compliant with USB 2.0 and USB 3.0 power specifications for input current and voltage regulation and meets USB On-the-Go (OTG) operation power rating specification with constant current limit up to 2.4A.

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 BQ25620 and BQ25622 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 BQ25620 and BQ25622 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 PG output indicates if a good power source is present. The INT output notifies the host when a fault occurs or status changes.

The BQ25620 and BQ25622 are available in a 18-pin, 2.5mm × 3.0mm WQFN package.