BQ24078RGTT

• Fully Compliant USB Charger
  • Selectable 100-mA and 500-mA Maximum Input Current
  • 100-mA Maximum Current Limit Ensures Compliance to USB-IF Standard
  • Input-Based Dynamic Power Management (VIN-DPM) forProtection Against Poor USB Sources
• 28-V Input Rating with Overvoltage Protection
• Integrated Dynamic Power Path Management (DPPM) Function Simultaneously andIndependently Powers the System and Charges the Battery
• Supports up to 1.5-A Charge Current with Current Monitoring Output(ISET)
• Programmable Input Current Limit up to 1.5 A for Wall Adapters
• System Output Tracks Battery Voltage
• Battery Disconnect Function with SYSOFF Input
• Programmable Pre-Charge and Fast-Charge Safety Timers
• Reverse Current, Short-Circuit, and Thermal Protection
• NTC Thermistor Input
• Proprietary Start-up Sequence Limits Inrush Current
• Battery Charge Voltage,VBAT:
  • bq24076 - 4.4 V (typ)
  • bq24078 - 4.35 V (typ)
• Status Indication – Charging/Done, Power Good

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The bq2407x is a family of integrated Li-Ion battery linear chargers with system powerpath management functionality targeted at space-constrained portable applications. The devicesoperate from either a USB port or an AC adapter and support charge currents up to 1.5 A. The inputvoltage range with input overvoltage protection supports unregulated adapters. The USB inputcurrent limit accuracy and start up sequence allow the bq2407x to meet USB-IF inrush currentspecifications. Additionally, the input dynamic power management (VIN-DPM)prevents system crashes because of incorrectly configured USB sources and maximizes the poweravailable from the adapter.

The bq2407x features dynamic power path management (DPPM) that powers the system whilesimultaneously and independently charging the battery. The DPPM circuit reduces the charge currentwhen the input current limit causes the system output to fall to the DPPM threshold; thus,supplying the system load at all times while monitoring the charge current separately. This featurereduces the number of charge and discharge cycles on the battery, allows for proper chargetermination and enables the system to run with a defective or absent battery pack.

Additionally, the regulated system input enables instant system turn-on when plugged ineven with a totally discharged battery. The power-path management architecture also lets thebattery supplement the system current requirements when the adapter cannot deliver the peak systemcurrents, thus enabling the use of a smaller adapter.

The battery is charged in three phases: conditioning, constant current, and constantvoltage. In all charge phases, an internal control loop monitors the IC junction temperature andreduces the charge current if the internal temperature threshold is exceeded. The charger powerstage and charge current sense functions are fully integrated. The charger function has highaccuracy current and voltage regulation loops, charge status display, and charge termination. Theinput current limit and charge current are programmable using external resistors.