Datasheet

bq24270

bq24271

SLUSB10 –JUNE 2012

www.ti.com

DETAILED DESCRIPTION

The bq24270 and bq24271 are highly integrated single cell Li-Ion battery chargers and system power path

management devices targeted for space-limited, portable applications with high capacity batteries. The single-

input, single cell charger operates from either a USB port or alternate power source (i.e. wall adapter or wireless

power input) for a versatile solution.

The power path management feature allows the bq24270 and bq24271 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. This allows for proper charge termination and enables the system to run with a

defective or absent battery pack. Additionally, this 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. This enables the use of

a smaller adapter. The charge parameters are programmable using the I

C interface.

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.

Charge Mode Operation

Charge Profile

The internal battery MOSFET is used to charge the battery. When the battery is above the MINSYS voltage, the

internal FET is on to maximize efficiency and the PWM converter regulates the charge current into the battery.

When battery is less than MINSYS, the SYS is regulated to V

SYS(REG)

and battery is charged using the battery

FET to regulate the charge current. There are 5 loops that influence the charge current:

• Constant current loop (CC)

• Constant voltage loop (CV)

• Thermal-regulation loop

• Minimum system-voltage loop (MINSYS)

• Input-voltage dynamic power-management loop (V

(IN-DPM)

)

During the charging process, all five loops are enabled and the one that is dominant takes control. The bq24270

supports a precision Li-Ion or Li-Polymer charging system for single-cell applications. The Dynamic Power Path

Management (DPPM) feature regulates the system voltage to a minimum of V

MINSYS

, so that startup is enabled

even for a missing or deeply discharged battery. Figure 3shows a typical charge profile including the minimum

system output voltage feature.

Product Folder Link(s): bq24270 bq24271