BQ24100_07 Datasheet, PDF(15/36 Page) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POLYMER CHARGE-MANAGEMENT IC WITH INTEGRATED POWER FETs (bqSWITCHER™)

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BQ24100_07 Datasheet, PDF (15/36 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POLYMER CHARGE-MANAGEMENT IC WITH INTEGRATED POWER FETs (bqSWITCHER™)

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bq24100, bq24103, bq24103A

bq24105, bq24108, bq24109

bq24113, bq24113A, bq24115

SLUS606K â JUNE 2004 â REVISED NOVEMBER 2007

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)

(2)

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. The

best accuracy is achieved when the VIREG is between 100mV and 200mV.

R(SNS)

VIREG

IOCHARGE

(3)

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

value, solve for VIREG. Once the sense resistor is selected, the ISET1 resistor can be calculated using the

following equation:

RISET1

KISET1

RSNS

VISET1

ICHARGE

(4)

Battery Voltage Regulation

The voltage regulation feedback occurs through the BAT pin. This input is tied directly to the positive side of the

battery pack. The bqSWITCHER monitors the battery-pack voltage between the BAT and VSS pins. The

bqSWITCHER is offered in a fixed single-cell voltage version (4.2 V) and as a one-cell or two-cell version

selected by the CELLS input. A low or floating input on the CELLS selects single-cell mode (4.2 V) while a

high-input through a resistor selects two-cell mode (8.4 V).

Charge Termination and Recharge

The bqSWITCHER monitors the charging current during the voltage regulation phase. Once the termination

threshold, ITERM, is detected, the bqSWITCHER terminates charge. The termination current level is selected by

the value of programming resistor, R(ISET2), connected to the ISET2 pin.

Ç ITERM + K(ISET2)

R(ISET2)

VTERM

Ç R(SNS)

(5)

where

R(SNS) is the external current-sense resistor

VTERM is the output of the ISET2 pin

K(ISET2) is the A/V gain factor

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

As a safety backup, the bqSWITCHER also provides a programmable charge timer. The charge time is

programmed by the value of a capacitor connected between the TTC pin and GND by the following formula:

tCHARGE + C(TTC) K(TTC)

(6)

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Product Folder Link(s): bq24100, bq24103, bq24103A bq24105, bq24108, bq24109 bq24113, bq24113A, bq24115

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