BQ24266_15 Datasheet, PDF (13/41 Pages) Texas Instruments – bq24266 3A, 30V Standalone Single-Input, Single-Cell Switchmode Li-Ion Battery Charger

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7 Detailed Description
bq24266
SLUSBY5F – JUNE 2014 – REVISED AUGUST 2015
7.1 Overview
The bq24266 is a highly integrated single cell Li-Ion battery charger and system power path management
devices targeted for space-limited, portable applications with high capacity batteries. The single cell charger has
a single input that supports operation from either a USB port or wall adapter supply for a versatile solution.
The power path management feature allows the bq24266 to power the system from a high efficiency DC to DC
converter while simultaneously and independently charging the battery. The charger monitors the battery current
at all times and reduces the charge current when the system load requires current above the input current limit or
the adapter cannot support the required load, causing the adapter voltage to fall (V_{IN_DPM}). This allows for proper
charge termination and timer operation. The system voltage is regulated to the battery voltage but will not drop
below 3.5V (V_MINSYS). This minimum system voltage support enables the system to run with a defective or absent
battery pack and enables instant system turn-on even with a totally discharged battery or no battery. The power-
path management architecture also permits the battery to supplement the system current requirements when the
adapter cannot deliver the peak system currents. The power-path feature coupled with V_IN-DPM, enables the use
of many adapters with no hardware change. The charge parameters are programmable using the ISET pin. To
support USB OTG applications, the bq24266 is configurable to boost the battery voltage to 5V at the input. In this
mode, the bq24266 supplies up to 1A and operates with battery voltages down to 3.3V.
The battery is charged using a standard Li-Ion charge profile with three phases: precharge, constant current and
constant voltage. In all charge phases, an internal control loop monitors the IC junction temperature and reduces
the input current to prevent the junction temperature from rising above 125°C. With the bq24266 a voltage-
based, JEITA compatible battery pack thermistor monitoring input (TS) is included that monitors battery
temperature and automatically changes charge parameters to prevent the battery from charging outside of its
safe temperature range.
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