PRODUCT DATASHEET
AAT2601178
Total Power Solution for Portable Applications
internal series pass MOSFET when the input-output volt-
age differential is at its highest.
Battery Charger
Figure 3 illustrates the entire battery charging profile
which consists of three phases.
Constant Current Mode Charge Current
1. Preconditioning Current Mode (Trickle) Charge
2. Constant Current Mode Charge
3. Constant Voltage Mode Charge
Trickle charge continues until the battery voltage reach-
es VMIN. At this point the battery charger begins con-
stant-current charging. The current level default for this
mode is programmed using a resistor from the ISET pin
to ground. Once that resistor has been selected for the
default charge current, then the current can be adjusted
through I2C from a range of 40% to 180% of the pro-
grammed default charge current. Programmed current
can be set at a minimum of 100mA and up to a maxi-
mum of 1A. When the ADPP signal goes high, the default
I2C setting of 100% is reset. If the USE_USB signal is
high when this happens, the charge current is reset to
an internally set 100mA current until the microcontroller
sends another I2C signal to change the charge current.
(see I2C Programming section).
Preconditioning Trickle Charge
Battery charging commences only after the AAT2601
battery charger checks several conditions in order to
maintain a safe charging environment. The system
operation flow chart for the battery charger operation is
shown in Figure 4. The input supply must be above the
minimum operating voltage (UVLO) and the enable pin
(ENBAT) must be low (it is internally pulled down).
When the battery is connected to the BAT pin, the bat-
tery charger checks the condition of the battery and
determines which charging mode to apply.
Constant Voltage Mode Charge
Preconditioning Current Mode
Charge Current
Constant current charging will continue until the battery
voltage reaches the Output Charge Voltage Regulation
If the battery voltage is below the preconditioning volt-
age threshold VMIN, then the battery charger initiates
precondition trickle charge mode and charges the bat-
tery at 12% of the programmed constant-current mag-
nitude. For example, if the programmed current is
500mA, then the trickle charge current will be 60mA.
Trickle charge is a safety precaution for a deeply dis-
charged cell. It also reduces the power dissipation in the
point VBAT_REG
.
When the battery voltage reaches the
regulation voltage (VBAT_REG), the battery charger will tran-
sition to constant-voltage mode. VBAT_REG is factory pro-
grammed to 4.2V (nominal). Charging in constant-voltage
mode will continue until the charge current has reduced
to the end of charge termination current programmed
using the I2C interface (5%, 10%, 15%, or 20%).
I (mA)
V (V)
Preconditioning
Trickle Charge
Phase
Constant Current
Charge Phase
Constant Voltage
Charge Phase
Battery End of Charge
Voltage Regulation (VBAT_REG
)
FAST-CHARGE to
TOP-OFF Charge
Threshold
Constant-Current Mode
Charge Current (ICH_CC
)
Charge Voltage
Preconditioning Threshold
Voltage (VMiN
)
Charge Current
Preconditioning Charge
Current (ICH_PRE
)
Charge Termination
Threshold Current
(ICH_TERM
)
T (s)
Trickle Charge
Timeout
(TK)
Constant Current Timeout
(TC
Constant Voltage Timeout
(TV
)
)
Figure 3: Current vs. Voltage and Charger Time Profile.
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2601.2008.01.1.0
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
