AAT3683 Datasheet, PDF (11/24 Pages) Advanced Analogic Technologies – 1A Linear Li-Ion Battery Charger

AAT3683
1A Linear Li-Ion Battery Charger
tally controlled thermal loop system that will reduce
the charging current to prevent the device from
thermal shutdown. The digital thermal loop will
maintain the maximum possible battery charging
current for the given set of input to output power
dissipation and ambient temperature conditions.
The digital thermal loop control is dynamic in the
sense that it will continue to adjust the battery
charging current as operating conditions change.
The digital thermal loop will reset and resume nor-
mal operation when the power dissipation or over-
temperature conditions are removed.
Battery Charging Operation
Figure 1 illustrates the entire battery charging pro-
file or operation, which consists of three phases:
1. Preconditioning (Trickle) Charge
2. Constant Current Charge
3. Constant Voltage Charge
Battery Preconditioning
Battery charging commences only after the
AAT3683 checks several conditions in order to
maintain a safe charging environment. The input
supply must be above the minimum operating volt-
age (V_UVLO) and the enable pin must be high.
When the battery is connected to the BAT pin, the
AAT3683 checks the condition of the battery and
determines which charging mode to apply. If the
battery voltage is below the preconditioning voltage
threshold, V_MIN, then the AAT3683 begins precon-
ditioning the battery cell (trickle charging) by charg-
ing at 10% of the programmed constant current.
For example, if the programmed current is 500mA,
then the preconditioning mode (trickle charge) cur-
rent is 50mA. Battery cell preconditioning (trickle
charging) is a safety precaution for deeply dis-
charged cells and will also reduce the power dissi-
pation in the internal series pass MOSFET when
the input-output voltage differential is at the great-
est potential.
Constant Current Charging
Battery cell preconditioning continues until the bat-
tery voltage reaches the preconditioning voltage
threshold, V_MIN. At this point, the AAT3683 begins
constant current charging. The current level for this
mode is programmed using a single resistor from
the ISET pin to ground. Programmed current can be
set at a minimum 100mA up to a maximum of 1A.
Constant Voltage Charging
Constant current charging will continue until such
time that the battery voltage reaches the voltage
regulation point, V_{BAT_EOC}. When the battery volt-
age reaches V_{BAT_EOC}, the AAT3683 will transition
to constant voltage mode. The regulation voltage is
factory programmed to a nominal 4.2V and will
continue charging until the charge termination cur-
rent is reached.
Charge Complete Voltage
Regulated Current
Preconditioning
Trickle Charge
Phase
Constant Current
Charge Phase
I = Max CC
Constant Voltage
Charge Phase
Constant Current Mode
Voltage Threshold
Trickle Charge and I = CC / 10
Termination Threshold
Figure 1: Current vs. Voltage Profile During Charging Phases.
3683.2007.06.1.0
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