SLUSA27 – MARCH 2010
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 normal charging process with host control, once the voltage at the CSOUT pin is above the battery
recharge threshold, VOREG- VRCH, and the termination charge current is detected, the IC turns off the PWM
charge and enables a discharge current, IDETECT, 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. On the
other hand, 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. This function ensures that the charge parameters are reset whenever the battery is replaced.
Battery Detection at Power Up
bq24153/6 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, bq24153/6 will start a 32ms timer when exiting from short circuit mode to PWM
charge mode. If the battery voltage is charged to recharge threshold (VOREG-VRCH) and the 32ms timer is not
expired yet, or battery voltage is above output OVP threshold during short-circuit mode, bq2153/6 will considered
that the battery is not present; then stop charging and go to high impedance mode immediately. However, if the
32ms timer is expired before the recharge threshold is reached, the charging process will continue as normal
battery charging process. For bq24158, the 32ms timer for battery detection at power up is disabled. Therefore,
bq24158 can power up the system without a battery.
Battery Short Protection
During the normal charging process, if the battery voltage is lower than the short-circuit threshold, VSHORT, the
charger operates in short circuit mode with a lower charge rate of ISHORT.
Charge Status Output, STAT Pin
The STAT pin is used to indicate operation conditions for bq24153/6/8. 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 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,
Boost mode faults (bq24153/8 only): Timer fault, over load,
VBUS or battery overvoltage, low battery voltage, thermal
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.
The RESET bit in the control register is used to reset all the charge parameters. Write ‘1” to RESET bit will reset
all the charge parameters to default values except 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 RESET bit when charging or boosting in progress.
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Product Folder Link(s): bq24153 bq24156 bq24158