AAT3663_08 Datasheet, PDF (13/23 Pages) Advanced Analogic Technologies – 1A Linear Li-Ion Battery Charger for Single and Dual Cell Applications

BatteryManager^TM
PRODUCT DATASHEET
AAT3663
1A Linear Li-Ion Battery Charger for Single and Dual Cell Applications
This open drain MOSFET switch may be used to either
power a display LED or to alert a system microcontroller
for the presence on input power.
Battery Charging Operation
Figure 1 illustrates the entire battery charging profile
and operation, which consists of three phases:
1. Preconditioning (Trickle) Charge
2. Constant Current Charge
3. Constant Voltage Charge
When power is initially applied or when a battery pack is
connected to the BAT pin, battery charging commences
after the AAT3663 checks several conditions in order to
maintain a safe charging environment. The input supply
must be above the minimum operating voltage (UVLO)
and the enable pin must be high (internally pulled
down). When the battery is connected to the BAT pin the
AAT3663 checks the condition of the battery and deter-
mines which charging mode to apply.
Battery Preconditioning
If the battery voltage is below V_MIN, the AAT3663 begins
battery trickle charging by charging at 10% of the pro-
grammed constant-current. For example, if the pro-
grammed current is 500mA, then the trickle charge
current is 50mA. Trickle charging is a recommended
safety precaution for a deeply discharged cell and maxi-
mizes the charge cycle life of the battery. In addition,
charger IC power dissipation for the internal series pass
MOSFET is minimized when the input-output voltage dif-
ferential is at its highest. This in turn allows the charg-
ing operation to commence over wider thermal and input
to output voltage differential conditions.
Constant Current Charging
Trickle charging continues until the battery voltage
reaches the V_MIN threshold. At this point, the AAT3663
begins constant-current fast 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 1A.
Constant Voltage Charging
Constant current charging continues until such time that
the battery voltage reaches the voltage regulation point
V_{BAT_REG}. When the battery voltage reaches V_{BAT_REG}, the
AAT3663 will transition to the constant-voltage mode.
The regulation voltage is factory programmed to a nom-
inal 4.2V for the AAT3663-4.2 option and to 8.4V for the
AAT3663-8.4 option. Under default conditions with the
TERM pin not connected (open circuit), constant voltage
charging will continue until the charge current has
reduced to 10% of the programmed current. Placing a
resistor between the TERM pin and ground allows the
user to program a desired termination current.
After the charge cycle is complete, the AAT3663 turns
off the series pass device and automatically goes into a
power saving sleep mode. During this time the series
pass device will block current in both directions there-
fore preventing the battery discharging through the IC.
The AAT3663 will remain in sleep mode, until either the
battery terminal voltage drops below the V_RCH threshold,
the charger EN pin is recycled or the charging power
source is reconnected. In all cases the AAT3663 will
monitor all battery parameters and resume charging in
the appropriate mode.
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 and Voltage Profile During Charging Phases.
3663.2008.01.1.2
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