The bq2407x is a family of integrated Li-Ion battery linear chargers with system power
path management functionality targeted at space-constrained portable applications. The devices
operate from either a USB port or an AC adapter and support charge currents up to 1.5 A. The input
voltage range with input overvoltage protection supports unregulated adapters. The USB input
current limit accuracy and start up sequence allow the bq2407x to meet USB-IF inrush current
specifications. Additionally, the input dynamic power management (VIN-DPM)
prevents system crashes because of incorrectly configured USB sources and maximizes the power
available from the adapter.
The bq2407x features dynamic power path management (DPPM) that powers the system while
simultaneously and independently charging the battery. The DPPM circuit reduces the charge current
when 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 feature
reduces the number of charge and discharge cycles on the battery, allows for proper charge
termination 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 in
even with a totally discharged battery. The power-path management architecture also lets the
battery supplement the system current requirements when the adapter cannot deliver the peak system
currents, thus enabling the use of a smaller adapter.
The battery is charged in three phases: conditioning, constant current, and constant
voltage. In all charge phases, an internal control loop monitors the IC junction temperature and
reduces the charge current if the internal temperature threshold is exceeded. The charger power
stage and charge current sense functions are fully integrated. The charger function has high
accuracy current and voltage regulation loops, charge status display, and charge termination. The
input current limit and charge current are programmable using external resistors.
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