BQ24100 Datasheet, PDF(15/26 Page) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POL CHARGE MANAGEMENT IC WITH INTEGRATED POWERFETS

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BQ24100 Datasheet, PDF (15/26 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POL CHARGE MANAGEMENT IC WITH INTEGRATED POWERFETS

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www.ti.com

bq24100, bq24103

bq24105, bq24108

bq24113, bq24115

SLUS606C â JUNE 2004 â REVISED SEPTEMBER 2005

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

R(ISET2)

K(ISET2)

R(SNS)

V(ISET2) + 1000 VÅA

IOPRECHG

0.05 W

0.1 V

0.2 A

(8)

RSENSE

SNS

BAT

ISET1

ISET2

VSS

V(ISET1) = 1 V

R(ISET1)

V(ISET2) = 0.1 V

I(ISET1)

R(ISET2)

I(ISET2)

UDG-04036

Figure 8. Program Charge Current with R(ISET1) and R(ISET2)

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 two fixed-voltage versions: 4.2 V and 8.4 V as selected by the CELLS input. A low or

floating input on the CELLS selects single-cell mode (4.2 V) while a high-input selects two-cell mode.

For device options that include adjustable output voltage, the voltage regulation feedback is through the FB pin.

A resistor divider is used from the battery output voltage to GND. The BAT pin remains connected directly to the

battery output voltage for current sensing with respect to SNS.

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)

(9)

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)

(10)

where

C(TTC) is the capacitor connected to the TTC pin

K(TTC) is the multiplier

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