BQ24020_07 Datasheet, PDF(13/22 Page) Texas Instruments – SINGLE-CHIP, LI-ION AND LI-POL CHARGER IC WITH AUTONOMOUS USB-PORT AND AC-ADAPTER SUPPLY MANAGEMENT (bqTINY-II)

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BQ24020_07 Datasheet, PDF (13/22 Pages) Texas Instruments – SINGLE-CHIP, LI-ION AND LI-POL CHARGER IC WITH AUTONOMOUS USB-PORT AND AC-ADAPTER SUPPLY MANAGEMENT (bqTINY-II)

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bq24020, bq24022, bq24023

bq24024, bq24025, bq24026

bq24027

SLUS549D â DECEMBER 2002 â REVISED MARCH 2006

FUNCTIONAL DESCRIPTION (continued)

BATTERY CHARGE CURRENT

The bqTINY-II offers on-chip current regulation with a programmable set point. The resistor connected between

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

specifications table.

Ç Ç K(SET) V(SET)

IO(OUT) +

RSET

(2)

When charging from a USB port, the host controller has the option of selecting either a 100-mA or a 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 OUT pin. This input is tied directly to the positive side of the

battery pack. The bqTINY-II monitors the battery-pack voltage between the OUT and VSS pins. When the

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

begins to taper down.

As a safety backup, the bqTINY-II also monitors the charge time. If the charge is not terminated within the time

period specified by t(CHG), the bqTINY-II turns off the charger and asserts a FAULT code on the STATx pins.

Please refer to the TIMER FAULT RECOVERY section for additional details.

CHARGE TAPER DETECTION, TERMINATION AND RECHARGE

The bqTINY-II monitors the charging current during the voltage-regulation phase. When the taper threshold,

I(TAPER), is detected, the bqTINY-II initiates the taper timer, t(TAPER). Charge is terminated after the timer expires.

The resistor connected between the ISET1 and VSS, 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)

The bqTINY-II resets the taper timer if the charge current rises above the taper threshold, I(TAPER).

In addition to taper-current detection, the bqTINY-II terminates charge if the charge current falls below the I(TERM)

threshold. This feature allows quick recognition of a battery-removal condition, or insertion of a fully charged

battery. Note that the charge timer and taper timer are bypassed for this feature. The resistor connected

between the ISET1 and VSS, RSET, determines the taper detection level. The V(TERM) and K(SET) parameters are

specified in the specifications table. Note that this applies to both AC and USB charging.

I (TERM)

V(TERM) K(SET)

RSET

(4)

After charge termination, the bqTINY-II re-starts the charge when the voltage on the OUT pin falls below the

V(RCH) threshold. This feature keeps the battery at full capacity at all times.

Note ON bq24026 AND bq24027

The bq24026 and bq24027 monitor the charging current during the voltage-regulation phase. Once the taper

threshold, I(TAPER), is detected, the bq24026/27 terminates the charge. There is no taper timer (t(TAPER)) for this

version.

The resistor connected between the ISET1 and VSS, RSET, determines the taper-detect level for AC input. For

USB charge, taper level is fixed at 10% of the 100- or 500-mA charge rate.

Also note that there is I(TERM) detection in the bq24026 and the bq24027.

SLEEP MODE

The bqTINY-II enters low-power sleep mode if both AC and USB are removed from the circuit. This feature

prevents draining the battery in the absence of input supply.

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