SLUS968G January 2010 – August 2015
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
The bq2409x series of devices are highly integrated Li-Ion and Li-Pol linear chargers devices targeted at space-limited portable applications. The devices operate from either a USB port or AC adapter. The high input voltage range with input overvoltage protection supports low-cost unregulated adaptors. These devices have a single power output that charges the battery. A system load can be placed in parallel with the battery as long as the average system load does not keep the battery from charging fully during the 10 hour safety timer.
RISET = [K(ISET) / I(OUT)]
from electrical characteristics table. . . K(SET) = 540AΩ
RISET = [540AΩ/0.54A] = 1.0 kΩ
Selecting the closest standard value, use a 1 kΩ resistor between ISET (pin 16) and VSS.
RPRE-TERM = K(TERM) × %IOUT-FC
RPRE-TERM = 200Ω/% × 10% = 2kΩ
Selecting the closest standard value, use a 2 kΩ resistor between ITERM (pin 15) and Vss.
One can arrive at the same value by using 20% for a pre-charge value (factor of 2 difference).
RPRE-TERM = K(PRE-CHG) × %IOUT-FC
RPRE-TERM = 100Ω/% × 20%= 2kΩ
Use a 10kΩ NTC thermistor in the battery pack (103AT).
To Disable the temp sense function, use a fixed 10kΩ resistor between the TS (Pin 1) and Vss.
LED Status: connect a 1.5kΩ resistor in series with a LED between the OUT pin and the CHG pin.
Connect a 1.5kΩ resistor in series with a LED between the OUT pin and the and PG pin.
Processor Monitoring: Connect a pull-up resistor between the processor’s power rail and the CHG pin.
Connect a pull-up resistor between the processor’s power rail and the PG pin.
In most applications, all that is needed is a high-frequency decoupling capacitor (ceramic) on the power pin, input and output pins. Using the values shown on the application diagram, is recommended. After evaluation of these voltage signals with real system operational conditions, one can determine if capacitance values can be adjusted toward the minimum recommended values (DC load application) or higher values for fast high amplitude pulsed load applications. Note if designed for high input voltage sources (bad adaptors or wrong adaptors), the capacitor needs to be rated appropriately. Ceramic capacitors are tested to 2x their rated values so a 16V capacitor may be adequate for a 30V transient (verify tested rating with capacitor manufacturer).
|Continuous battery detection when not in TTDM.|
|CH4: Iout (1A/Div)|
|CH4: Iout (1A/Div)|
|Battery voltage swept from 0V to 4.25V to 3.9V.|
|CH4: Iout (0.2A/Div)|