BQ24075T Datasheet, PDF(20/29 Page) Texas Instruments – 1.5A USB-Friendly Li-Ion Battery Charger and Power-Path Management IC

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BQ24075T Datasheet, PDF (20/29 Pages) Texas Instruments – 1.5A USB-Friendly Li-Ion Battery Charger and Power-Path Management IC

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bq24075T

bq24079T

SLUS937 â DECEMBER 2009

Table 2. PGOOD Status Indicator

INPUT STATE

VIN < VUVLO

VUVLO < VIN < VIN(DT)

VIN(DT) < VIN < VOVF

VIN < VOVP

PGOOD OUTPUT

Hi impedance

Low

Hi impedance

Table 3. CHG Status Indicator

CHARGE STATE

Charging

Charging suspended by thermal loop, or DPPM loop

Safety timers expired

Charging done

Recharging after termination

IC disabled or no valid input power

Battery absent

CHG OUTPUT

Low (for first charge cycle)

Flashing at 2 Hz

Hi impedance

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THERMAL REGULATION AND THERMAL SHUTDOWN

The bq2407xT contain a thermal regulation loop that monitors the die temperature. If the temperature exceeds

TJ(REG), the device automatically reduces the charging current to prevent the die temperature from increasing

further. In some cases, the die temperature continues to rise despite the operation of the thermal loop,

particularly under high VIN and heavy OUT system load conditions. Under these conditions, if the die temperature

increases to TJ(OFF), the input FET Q1 is turned OFF. FET Q2 is turned ON to ensure that the battery still powers

the load on OUT. Once the device die temperature cools by TJ(OFF-HYS), the input FET Q1 is turned on and the

device returns to thermal regulation. Continuous overtemperature conditions result in a "hiccup" mode. During

thermal regulation, the safety timers are slowed down proportionately to the reduction in current limit.

Note that this feature monitors the die temperature of the bq2407xT. This is not synonymous with ambient

temperature. Self heating exists due to the power dissipated in the IC because of the linear nature of the battery

charging algorithm and the LDO associated with OUT. A modified charge cycle with the thermal loop active is

shown in Figure 29. Battery termination is disabled during thermal regulation.

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