BQ24153A_14 Datasheet, PDF (18/46 Pages) Texas Instruments – Fully Integrated Switch-Mode One-Cell Li-Ion Charger With Full USB Compliance and USB-OTG Support

bq24153A, bq24156A
bq24158, bq24159
SLUSAB0C – OCTOBER 2010 – REVISED JULY 2013
www.ti.com
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.
Battery Detection at Power Up in 15-minute Mode (bq24153A/6A only)
bq24153A/6A also have a unique battery detection scheme during the start up of the charger. At VBUS power
up, if the timer is in 15-minute mode, bq24153A/6A will start a 262ms timer when exiting from short circuit mode
to PWM charge mode. If the battery voltage is charged above the recharge threshold (V_OREG-VRCH) when the
262ms timer expired, bq2153A/6A will not consider the battery present; then stop charging, and go to high
impedance mode immediately. However, if the battery voltage is still below the recharge threshold when the
262ms timer expires, the charging process will continue as normal battery charging process.
bq24158/9 simply begin regulating the output voltage to their default values (3.54V) at power up while in 15-
minute mode.
Battery Detection in Host Mode
For applications with removable battery packs, the IC provides a battery absent detection scheme to reliably
detect insertion or removal of battery packs.
During the normal charging process with host control, once the voltage at the CSOUT pin is above the battery
recharge threshold, V_OREG- V_RCH, and the termination charge current is detected, the IC turns off the PWM
charge and enables a discharge current, I_DETECT, for a period of t_DETECT, (262 ms typical) then checks the battery
voltage. If the battery voltage is still above the recharge threshold after t_DETECT, the battery is present. On the
other hand, if the battery voltage is below the 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 T_INT. This function ensures that the charge parameters are reset whenever the battery is
replaced.
15-MINUTE SAFETY TIMER AND 32-SECOND WATCHDOG TIMER IN CHARGE MODE
Once a good adapter and good battery are attached, the IC starts the 15-minute saftey timer (t15min) that can be
disabled by any write-action performed by host through I²C interface. Once the 15-minute timer is disabled, a 32-
second watchdog timer (t32sec) is automatically started. The 32-second timer can be reset by the host using I2C
interface. Writing “1” to reset the TMR_RST bit in the control register will reset the 32-second timer and
TMR_RST is automatically set to “0” after the 32-second timer is reset. If the 32-second timer expires, the charge
is terminated and charge parameters are reset to default values. Then the 15-minute timer starts and the charge
resumes in 15-minute mode.
During normal charging process, the IC is usually in 32-second mode with host control and 15-minute mode
without host control using I²C interface. The above process repeats until the battery is fully charged. If the 15-
minute timer expires, the IC turns off the charge, enunciates FAULT on the STATx bits of status register, and
sends the 128μs interrupt pulse. This function prevents battery over charge if the host fails to reset the safety
timer. The 15-minute charge, with default parameters, allows time for a discharged battery to charge sufficiently
to be able to power the host and start communication. The safety timer flow chart is shown in Figure 29. Fault
condition is cleared by POR and fault status bits can only be updated after the status bits are read by the host.
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