Indicate Pre鈭?/div>
Charge
No
Regulate Current
or Voltage
Indicate Charge
Yes
V
I(VSENSE)
> V
(OVERV)
?
No
No
V
I(VSENSE)
> V
(OVERV)
?
Yes
V
I(VSENSE)
< V
(LOWV)
?
No
Yes
Yes
V
I(VSENSE)
< V
(LOWV)
?
22.5 min Timer
Expired?
No
No
Yes
Fault Condition
Indicate Fault
POR?
or
APG/THERM Toggle?
No
Yes
Figure 15. Operational Flow Chart With the Charge Timers Disabled (TMR EN = 1)
Charge Qualification and Preconditioning
The bq2400x starts a charge cycle when power is applied
while a battery is present. Charge qualification is based on
battery voltage and the APG/THERM input.
As shown in the block diagram, the internal LowV
comparator output prevents fast-charging a deeply
depleted battery. When set, charging current is provided
by a dedicated precharge current source. The precharge
timer limits the precharge duration. The precharge current
also minimizes heat dissipation in the pass element during
the initial stage of charge.
The APG/THERM input can also be configured to monitor
14
either the adapter power or the battery temperature using
a thermistor. The bq2400x suspends charge if this input is
outside the limits set by the user. Please refer to the
APG/THERM input section for additional details.
Timer Enable Function
The logic TRM EN enables or disables the charge safety
timer. A low-level signal on this pin enables the timer
(charge and taper). A high-level input disables the timers
and allows the charger to operate continuously. No charge
termination is provided when this input is high. Note that
the preconditioning timer remains active regardless of the
status of this input.
The TRM EN input can be changed any time during the
charge cycle. A low-to-high transition on this pin resets the
timers.