BQ24100 Datasheet, PDF(13/26 Page) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POL CHARGE MANAGEMENT IC WITH INTEGRATED POWERFETS

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BQ24100 Datasheet, PDF (13/26 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POL CHARGE MANAGEMENT IC WITH INTEGRATED POWERFETS

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bq24100, bq24103

bq24105, bq24108

bq24113, bq24115

SLUS606C â JUNE 2004 â REVISED SEPTEMBER 2005

FUNCTIONAL DESCRIPTION FOR STAND-ALONE VERSION (bq2410x) (continued)

VCC

Charge Suspend

V(LTF)

V(HTF)

V(TCO)

VSS

Temperature Range

to Initiate Charge

Charge Suspend

Temperature Range

During Charge Cycle

Charge Suspend

Figure 7. TS Pin Thresholds

Battery Preconditioning (Precharge)

On power up, if the battery voltage is below the VLOWV threshold, the bqSWITCHER applies a precharge current,

IPRECHG, to the battery. This feature revives deeply discharged cells. The bqSWITCHER activates a safety timer,

tPRECHG, during the conditioning phase. If the VLOWV threshold is not reached within the timer period, the

bqSWITCHER turns off the charger and enunciates FAULT on the STATx pins. In the case of a FAULT

condition, the bqSWITCHER reduces the current to IDETECT. IDETECT is used to detect a battery replacement

condition. Fault condition is cleared by POR or battery replacement.

The magnitude of the precharge current, IO(PRECHG), is determined by the value of programming resistor, R(ISET2),

connected to the ISET2 pin.

Ç IO(PRECHG) + K(ISET2)

R(ISET2)

V(ISET2)

Ç R(SNS)

(1)

where

RSNS is the external current-sense resistor

V(ISET2) is the output voltage of the ISET2 pin

K(ISET2) is the V/A gain factor

V(ISET2) and K(ISET2) are specified in the Electrical Characteristics table.

Battery Charge Current

The battery charge current, IO(CHARGE), is established by setting the external sense resistor, R(SNS), and the

resistor, R(ISET1), connected to the ISET1 pin.

In order to set the current, first choose R(SNS) based on the regulation threshold VIREG across this resistor. Let

VIREG = 100 mV to start and calculate the RSNS value needed.

R(SNS)

VIREG

IOCHARGE

(2)

If this value is not a standard sense resistor value, choose the next larger value. Using the selected standard

value, solve for VIREG.

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