Datasheet

bq24230
bq24232
SLUS821E –OCTOBER 2008–REVISED JANUARY 2014 www.ti.com
Status Indicators (PGOOD, CHG)
The bq2423x contains two open-drain outputs that signal its status. The PGOOD output signals when a valid
input source is connected. PGOOD is low when (V
BAT
+ V
IN(DT)
) < V
IN
< V
OVP
. When the input voltage is outside
of this range, PGOOD is high impedance.
The CHG output signals when a new charge cycle is initiated. After a charge cycle is initiated, CHG goes low
once the battery is above the short-circuit threshold. CHG goes high impedance once the charge current falls
below I
TERM
. CHG remains high impedance until the input power is removed and reconnected or the CE pin is
toggled. It does not signal subsequent recharge cycles.
Table 2. PGOOD Status Indicator
Input State PGOOD Output
V
IN
< V
UVLO
Hi impedance
V
UVLO
< V
IN
< V
IN(DT)
+ V
BAT
Hi impedance
V
IN(DT)
+ V
BAT
< V
IN
< V
OVP
Low
V
IN
> V
OVP
Hi impedance
Table 3. CHG Status Indicator
Charge State CHG Output
Charging Low (first charge cycle)
Charging terminated Hi impedance until power or CE is toggled
Recharging after termination Hi impedance
Carging suspended by thermal loop Low (first charge cycle)
Safety timers expired Flashing at 2Hz
IC disabled or no valid input power Hi impedance
Timer Fault
If the precharge timer expires before the battery voltage reaches V
LOWV
, the bq2423x indicates a fault condition.
Additionally, if the battery current does not fall to I
TERM
before the fast-charge timer expires, a fault is indicated.
The CHG output flashes at approximately 2 Hz to indicate a fault condition.
Thermal Regulation And ThermaL Shutdown
The bq2423x contain a thermal regulation loop that monitors the die temperature. If the die temperature exceeds
T
J(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 T
J(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 T
J(OFF-HYS)
, the input FET Q1 is
turned on and the device returns to thermal regulation. Continuous overtemperature conditions result in a hiccup
mode. Safety timers are slowed proportionally to the charge current in thermal regulation. Battery termination is
disabled during thermal regulation and thermal shutdown.
Note that this feature monitors the die temperature of the bq2423x. 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 mode for OUT.
A modified charge cycle with the thermal loop active is shown in Figure 30:
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