BQ25015 Datasheet, PDF(12/28 Page) Texas Instruments – SINGLE-CHIP CHARGER AND DC/DC CONVERTER IC FOR PORTABLE APPLICATIONS

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BQ25015 Datasheet, PDF (12/28 Pages) Texas Instruments – SINGLE-CHIP CHARGER AND DC/DC CONVERTER IC FOR PORTABLE APPLICATIONS

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bq25015

bq25017

SLUS721A â DECEMBER 2006 â REVISED MARCH 2007

www.ti.com

FUNCTIONAL DESCRIPTIONS (continued)

Autononous Power Source Selection

As default, the bq25015/7 attempts to charge the battery from the AC input. If AC input is not present, the USB

input is selected. If both inputs are available, the AC adapter has the priority. Refer to Figure 15 for details.

AC > BATTERY

AC MODE

USB MODE

AC < BATTERY

USB > BATTERY

Figure 15. Power Source Selection

Battery Pre-Conditioning

During a charge cycle if the battery voltage is below the V(LOWV) threshold, the bq25015/7 applies a precharge

current, IO(PRECHG), to the battery. This feature revives deeply discharged cells. The resistor connected between

the ISET1 and VSS pins, RSET, determines the precharge rate. The V(PRECHG) and K(SET) parameters are

specified in the specifications table.

(PRECHG)

V(PRECHG)

RSET

K(SET)

(1)

The bq25015/7 activates a safety timer, t(PRECHG), during the conditioning phase. If V(LOWV) threshold is not

reached within the timer period, the bq25015/7 turns off the charger and enunciates FAULT on the STAT1 and

STAT2 pins. Please refer to Timer Fault Recovery section for additional details.

Battery Charge Current

The bq25015/7 offers on-chip current regulation with programmable set point. The resistor connected between

the ISET1 and VSS pins, RSET, determines the charge rate. The V(SET) and K(SET) parameters are specified in the

specifications table.

(OUT)

V(SET) K(SET)

RSET

(2)

When charging from a USB port, the host controller has the option of selecting either 100 mA or 500 mA charge

rate using the ISET2 pin. A low-level signal sets the current at 100 mA and a high-level signal sets the current at

500 mA. A high-Z input disables USB charging.

Battery Voltage Regulation

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

battery pack. The bq25015/7 monitors the battery-pack voltage between the BAT/OUT and VSS pins. When the

battery voltage rises to VO(REG) threshold, the voltage regulation phase begins and the charging current begins to

taper down.

As a safety backup, the bq25015/7 also monitors the charge time in the charge mode. If taper threshold is not

detected within this time period, t(CHG), the bq25015/7 turns off the charger and enunciates FAULT on the STAT1

and STAT2 pins. Please refer to section titled Timer Fault Recoverysection for additional details.

Charge Taper Detection, Termination and Regharge

The bq25015/7 monitors the charging current during the voltage regulation phase. Once the taper threshold,

I(TAPER), is detected the bq25015/7 initiates the taper timer, t(TAPER). Charge is terminated after the timer expires.

The resistor connected between the ISET1 and VSS pins, RSET, determines the taper detection level. The

V(TAPER) and K(SET) parameters are specified in the specifications table. Note that this applies to both AC and

USB charging.

I (TAPER)

V(TAPER)

RSET

K(SET)

(3)

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