BQ24153A Datasheet, PDF (22/43 Pages) Texas Instruments – Fully Integrated Switch-Mode One-Cell Li-Ion Charger

bq24153A
bq24156A, bq24158
SLUSAB0 – OCTOBER 2010
www.ti.com
Battery Detection During Normal Charging
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, then checks the battery voltage. If the
battery voltage is still above the recharge threshold, the battery is present and the charge done is detected. 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.
Battery Detection at Power Up
Bq24153A/6A also has 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.
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.
Charge Status Output, STAT Pin
The STAT pin is used to indicate operation conditions for bq24153A/6A/8. STAT is pulled low during charging
when EN_STAT bit in control register (00H) is set to “1”. Under other conditions, STAT pin behaves as a high
impedance (open-drain) output. Under fault conditions, a 128-µs pulse will be sent out to notify the host. The
status of STAT pin at different operation conditions is summarized in Table 1. The STAT pin can be used to drive
an LED or communicate to the host processor.
Table 1. STAT Pin Summary
CHARGE STATE
Charge in progress and EN_STAT=1
Other normal conditions
Charge mode faults: Timer fault, sleep mode, VBUS or battery
overvoltage, poor input source, VBUS UVLO, no battery,
thermal shutdown
Boost mode faults (bq24153A/8 only): Timer fault, over load,
VBUS or battery overvoltage, low battery voltage, thermal
shutdown
STAT
Low
Open-drain
128-ms pulse, then open-drain
128-ms pulse, then open-drain
Control Bits in Charge Mode
CE Bit (Charge Mode)
The CE bit in the control register is used to disable or enable the charge process. A low logic level (0) on this bit
enables the charge and a high logic level (1) disables the charge.
RESET Bit
The RESET bit in the control register is used to reset all the charge parameters. Writing ‘1” to the RESET bit will
reset all the charge parameters to default values except the safety limit register, and RESET bit is automatically
cleared to zero once the charge parameters get reset. It is designed for charge parameter reset before charge
starts and it is not recommended to set the RESET bit while charging or boosting are in progress.
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