BQ24075-Q1_15 Datasheet, PDF(19/38 Page) Texas Instruments – SLUSAU3B –FEBRUARY 2012

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BQ24075-Q1_15 Datasheet, PDF (19/38 Pages) Texas Instruments – SLUSAU3B –FEBRUARY 2012–REVISED MARCH 2012

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bq24075-Q1

www.ti.com

SLUSAU3B â FEBRUARY 2012 â REVISED MARCH 2012

INPUT SOURCE NOT CONNECTED

When no source is connected to the IN input, OUT is powered strictly from the battery. During this mode the

current into OUT is not regulated, similar to Battery Supplement Mode, however the short circuit circuitry is

active. If the OUT voltage falls below the BAT voltage by 250mV for longer than tDGL(SC2), OUT is turned off. The

short circuit recovery timer then starts counting. After tREC(SC2), OUT turns on and attempts to restart. If the short

circuit remains, OUT is turned off and the counter restarts. This ON/OFF cycle continues until the overload

condition is removed.

BATTERY CHARGING

Set CE low to initiate battery charging. First, the device checks for a short-circuit on the BAT pin by sourcing

IBAT(SC) to the battery and monitoring the voltage. When the BAT voltage exceeds VBAT(SC), the battery charging

continues. The battery is charged in three phases: conditioning pre-charge, constant current fast charge (current

regulation) and a constant voltage tapering (voltage regulation). In all charge phases, an internal control loop

monitors the IC junction temperature and reduces the charge current if an internal temperature threshold is

exceeded.

Figure 28 illustrates a normal Li-Ion charge cycle using the bq24075-Q1:

PRECHARGE

CC FAST CHARGE

CV TAPER

DONE

VBAT(REG)

IO(CHG)

Battery Current

VLOWV

I(PRECHG)

I(TERM)

Battery Voltage

CHG = Hi-z

Figure 28. Typical Charge Cycle

In the pre-charge phase, the battery is charged at with the pre-charge current (IPRECHG). Once the battery voltage

crosses the VLOWV threshold, the battery is charged with the fast-charge current (ICHG). As the battery voltage

reaches VBAT(REG), the battery is held at a constant voltage of VBAT(REG) and the charge current tapers off as the

battery approaches full charge. When the battery current reaches ITERM, the CHG pin indicates charging done by

going high-impedance.

Note that termination detection is disabled whenever the charge rate is reduced because of the actions of the

thermal loop, the DPPM loop or the VIN(LOW) loop.

The value of the fast-charge current is set by the resistor connected from the ISET pin to VSS, and is given by

the equation

ICHG = KISET/RISET

Product Folder Link(s): bq24075-Q1

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