The BQ25792 is a fully integrated switch-mode buck-boost charger for 1-4 cellLi-ion battery and Li-polymer battery. The integration includes 4 switching MOSFETs(Q1, Q2, Q3,Q4), input and charging current sensing circuits, the battery FET(QBAT) and all the loop compensation of the buck-boost converter. Itprovides high power density and design flexibility to charge batteries across the full inputvoltage range for USB Type-C™ and USB power delivery (USB-PD) applications such as smart phone,tablet and other portable devices.
The charger supports the narrow VDCpower path management, in which the system is regulated at a voltage slightly higher than thebattery voltage, but not drop below the minimum system voltage. The system keeps operating evenwhen the battery is completely discharged or removed. When load power exceeds input source rating,the battery gets into supplement mode and prevents the input source from being overloaded and thesystem from crashing.
The device charges a battery from awide range of the input sources including legacy USB adapter to high voltage USB PD adapter andtraditional barrel adapter. The charger automatically sets converter to be buck, boost orbuck-boost configurations based on input voltage and battery voltage without the host control. Thedual input source selector manages the power flowing from two different input sources. The inputsselection is controlled by the host through I2C with default source #1(VAC1) as the primary input and the source #2 (VAC2) as the secondary input.
To support fast charging usingadjustable high voltage adapter, the device provides D+/D- handshake. The device is compliant withUSB 2.0 and USB 3.0 power delivery specification with input current and voltage regulation. Inaddition, the Input Current Optimizer (ICO) allows the detection of maximum power point of anunknown input source.
Besides theI2C host controlled charging mode, this charger also supports autonomouscharging mode. After power up, the charging is enabled with default register settings. The devicecan complete a charging cycle without any software engagements. It detects battery voltage andcharges the battery in different phases: trickle charging, pre-charging, constant current (CC)charging and constant voltage (CV) charging. At the end of the charging cycle, the chargerautomatically terminates when the charge current is below a pre-set limit (termination current) inthe constant voltage phase. When the full battery falls below the recharge threshold, the chargerwill automatically start another charging cycle.
In the absence of input sources,this device supports USB On-the-Go (OTG) function, discharging battery to generate an adjustable2.8V~22V voltage on VBUS with 10mV step size, which is compliant to the USB PD 3.0 specificationdefined programmable power supply (PPS) feature.
The charger provides various safetyfeatures for battery charging and system operations, including battery temperature negativethermistor monitoring, trickle charge, pre-charge and fast charge timers andover-voltage/over-current protections on battery and input. The thermal regulation reduces chargecurrent when the junction temperature exceeds a programmable threshold. The STAT output of thedevice reports the charging status and any fault conditions. The PG outputindicates if a good power source is present. The INT pin immediatelynotifies host when fault occurs.
The device also provides a 16-bitanalog-to-digital converter (ADC) for monitoring charge current and input/battery/system (VAC,VBUS, BAT, SYS, TS) voltages.
It is available in a 29-pin 4mm × 4mm QFNpackage.