BQ24152 Datasheet, PDF(18/38 Page) Texas Instruments – Fully Integrated Switch-Mode One-Cell Li-Ion Charger with Full USB Compliance and USB-OTG Support

◁

bq24152

SLUS847 â JUNE 2008 ...................................................................................................................................................................................................... www.ti.com

Input Voltage Protection in Charge Mode

Sleep Mode

The bq24152 enters the low-power sleep mode if the voltage on VBUS pin falls below sleep-mode entry

threshold, VAUXPWR + VSLP, and VBUS is still higher than the poor source detection threshold, VIN(min). This

feature prevents draining the battery during the absence of VBUS. During sleep mode, both the reverse blocking

switch Q1 and PWM are turned off.

Input Source Detection

During the charging process, bq24152 continuously monitors the input voltage, VBUS. If VBUS falls to the low

input voltage threshold, VIN(min), poor input power source is detected. Under this condition, bq24152 terminates

the charge process, waits for a delay time of TINT and repeats the charging process, as indicated in Figure 23.

This unique function provides intelligence to bq24152 and so prevents USB power bus collapsing and oscillation

when connecting to a suspended USB port, or a USB-OTG device with low current capability.

Input Overvoltage Protection

The bq24152 provides a built-in input over-voltage protection to protect the device and other components against

damages if the input voltage (Voltage from VBUS to PGND) goes too high. When an input overvoltage condition

is detected, bq24152 turns off the PWM converter, sets fault status bits, and sends out fault pulse in STAT pin.

Once VBUS drops below the input overvoltage exit threshold, the fault is cleared and charge process resumes.

Battery Protection in Charge Mode

Output Overvoltage Protection

The bq24152 provides a built-in overvoltage protection to protect the device and other components against

damage if the battery voltage goes too high, as when the battery is suddenly removed. When an overvoltage

condition is detected, bq24152 turns off the PWM converter, sets fault status bits and sends out fault pulse in

STAT pin. Once V(CSOUT) drops to the battery overvoltage exit threshold, the fault is cleared and charge process

back to normal.

Battery Detection During Normal Charging

For applications with removable battery packs, the bq24152 provides a battery absent detection scheme to

reliably detect insertion or removal of battery packs.

During normal charging process with host control, once the voltage at the AUXPWR pin is above the battery

recharge threshold, V(OREG) â V(RCH), and the termination charge current is detected, bq24152 turns off the

charge and enables a discharge current, I(DETECT), for a period of tDETECT, then checks the battery voltage. If the

battery voltage is still above recharge threshold, the battery is present and the charge done is detected.

However, if the battery voltage is below battery recharge threshold, the battery is absent. Under this condition,

the charge parameters (such as input current limit) are reset to the default values and charge resumes after a

delay of TINT, as shown in Figure 23. This function ensures that the charge parameters are reset whenever the

battery is replaced.

Power Up Without Battery

When no battery is present, at VBUS power up, bq24152 will charge the output capacitor in short circuit mode

(when VAUXPWR<VSHORT) or PWM mode (when VAUXPWR>VSHORT). Once the output voltage at CSOUT pin is

charged to the default regulation voltage (3.54V), the voltage is kept constant until the 32-minute timer expires or

the host takes over the control through I2C interface. This unique feature makes bq24152 capable of starting the

system without battery.

Battery Short Protection

During the normal charging process, if the battery voltage is lower than the short-circuit threshold, V(SHORT), the

charger operates in short circuit mode with a lower charge rate of I(SHORT), as shown in Figure 22.

Submit Documentation Feedback

Product Folder Link(s): bq24152

▷