AAT2601 Analogic Corporation, AAT2601 Datasheet - Page 22

• Manufacturer Part Number: AAT2601
• Manufacturer: Analogic Corporation

Battery Charger
Figure 3 illustrates the entire battery charging profile
which consists of three phases.
1. Preconditioning Current Mode (Trickle) Charge
2. Constant Current Mode Charge
3. Constant Voltage Mode Charge
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.
Preconditioning Current Mode
Charge Current
If the battery voltage is below the preconditioning volt-
age threshold V
precondition trickle charge mode and charges the bat-
tery at 12% of the programmed constant-current mag-
nitude.
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
22
For example, if the programmed current is
MIN
, then the battery charger initiates
Figure 3: Current vs. Voltage and Charger Time Profile.
Constant-Current Mode
Charge Current (I
Preconditioning Charge
Current (I
Charge Termination
Threshold Current
(I
CH_TERM
CH_PRE
)
)
CH_CC
I (mA)
)
Preconditioning
Trickle Charge
Trickle Charge
Timeout
Phase
(T
K
)
w w w . a n a l o g i c t e c h . c o m
Constant Current Timeout
Constant Current
Charge Phase
Charge Voltage
(T
C
)
Total Power Solution for Portable Applications
Charge Current
internal series pass MOSFET when the input-output volt-
age differential is at its highest.
Constant Current Mode Charge Current
Trickle charge continues until the battery voltage reach-
es V
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 I
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
I
high when this happens, the charge current is reset to
an internally set 100mA current until the microcontroller
sends another I
(see I
Constant Voltage Mode Charge
Constant current charging will continue until the battery
voltage reaches the Output Charge Voltage Regulation
point V
regulation voltage (V
sition to constant-voltage mode. V
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 I
2
C setting of 100% is reset. If the USE_USB signal is
FAST-CHARGE to
TOP-OFF Charge
Constant Voltage Timeout
Threshold
Constant Voltage
Charge Phase
MIN
2
C Programming section).
(T
. At this point the battery charger begins con-
V
BAT_REG
)
2
C from a range of 40% to 180% of the pro-
2
C interface (5%, 10%, 15%, or 20%).
.
Battery End of Charge
Voltage Regulation (V
Preconditioning Threshold
Voltage (V
V (V)
2
When the battery voltage reaches the
C signal to change the charge current.
T (s)
MiN
)
BAT_REG
PRODUCT DATASHEET
BAT_REG
)
), the battery charger will tran-
AAT2601178
BAT_REG
2601.2008.01.1.0
is factory pro-