AAT3663 Datasheet, PDF (11/22 Pages) Advanced Analogic Technologies – 1A Linear Li-Ion Battery Charger for Single and Dual Cell Applications

AAT3663
1A Linear Li-Ion Battery Charger
for Single and Dual Cell Applications
indicate the presence of power on the input supply pin.
This open drain MOSFET switch may be used to either
power a display LED or to alert a system microcon-
troller 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 com-
mences 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 (inter-
nally pulled down). When the battery is connected to
the BAT pin the AAT3663 checks the condition of the
battery and determines 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 cur-
rent is 50mA. Trickle charging is a recommended safe-
ty 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
differential is at its highest. This in turn allows the
charging 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 resis-
tor 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 pro-
grammed to a nominal 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 pro-
grammed 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 thresh-
old, 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.
3663.2007.10.1.0
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