BQ24257 Datasheet, PDF (17/45 Pages) Texas Instruments – 2A Single Input I2C, Standalone Switch-Mode Li-Ion Battery Charger with Integrated Current Sense Resistor

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CHARGE PROFILE
bq24257
bq24258
SLUSBG0B – FEBRUARY 2013 – REVISED JULY 2013
The bq24257 family provides a switch-mode buck regulator with output non-power path and a charge controller
to provide optimum performance over the full battery charge cycle. The control loop for the buck regulator has 6
primary feedback loops that can set the duty cycle:
1. Constant Current (CC)
2. Constant Voltage (CV)
3. Input Current (I_ILIM)
4. Input Voltage (V_{IN_DPM})
5. Die Temperature
6. Cycle by Cycle Current
The feedback with the minimum duty cycle will be chosen as the active loop. The bq24257 supports a precision
Li-Ion or Li-Polymer charging system for single-cell applications. The bq24257 includes an integrated charge
sense resistor for highly accurate charge current sensing while reducing the external BOM requirements. The
figure below illustrates a typical charge profile.
Trickle
Charge
V_BATREG
Pre-
charge
Current Regulation
Phase (CC)
I_CHG
Voltage Regulation
Phase (CV)
Termination
I_CHG
V_CSIN
V_BAT
V_LOWV
V_BATSHRT
Charging on
Charge done
I_PRECHG
I_TERM
I_BATSHRT
The bq24258 supports an advanced Lithium-Iron-Phosphate (LiFePO₄) algorithm. This allows for the charger to
source the charge current up to the V_REG-OVCHG level before entering the float charge region. See below for the
charge profile characteristics:
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