AAT3683_08 Datasheet, PDF (11/23 Pages) Advanced Analogic Technologies – 1A Linear Li-Ion Battery Charger

BatteryManager^TM
The digital thermal loop control is dynamic in the sense
that it will continue to adjust the battery charging cur-
rent as operating conditions change.
The digital thermal loop will reset and resume normal
operation when the power dissipation or over-tempera-
ture conditions are removed.
Battery Charging Operation
Figure 1 illustrates the entire battery charging profile 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 voltage (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 bat-
tery and determines which charging mode to apply. If
the battery voltage is below the preconditioning voltage
threshold, V_MIN, then the AAT3683 begins precondition-
ing the battery cell (trickle charging) by charging at
PRODUCT DATASHEET
AAT3683
1A Linear Li-Ion Battery Charger
10% of the programmed constant current. For example,
if the programmed current is 500mA, then the precon-
ditioning mode (trickle charge) current is 50mA. Battery
cell preconditioning (trickle charging) is a safety precau-
tion for deeply discharged cells and will also reduce the
power dissipation in the internal series pass MOSFET
when the input-output voltage differential is at the
greatest potential.
Constant Current Charging
Battery cell preconditioning continues until the battery
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 voltage reaches V_{BAT_EOC},
the AAT3683 will transition to constant voltage mode.
The regulation voltage is factory programmed to a nom-
inal 4.2V and will continue charging until the charge
termination current 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.
3683.2007.11.1.2
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