AAT2556
Battery Charger and Step-Down
Converter for Portable Applications
Preconditioning
Trickle Charge
Phase
Constant Current
Charge Phase
Constant Voltage
Charge Phase
Charge Complete Voltage
Regulated Current
I = Max CC
Constant Current Mode
Voltage Threshold
Trickle Charge and
I = CC / 10
Termination Threshold
Figure 1: Current vs. Voltage Profile During Charging Phases.
Pre-conditioning continues until the battery voltage
After the charge cycle is complete, the pass device
turns off and the device automatically goes into a
power-saving sleep mode. During this time, the
series pass device will block current in both direc-
tions, preventing the battery from discharging
through the IC.
reaches VMIN. At this point, the charger begins con-
stant-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 from a minimum 15mA up to a maximum of
500mA. Constant current charging will continue
until the battery voltage reaches the voltage regu-
lation point, VBAT. When the battery voltage reach-
es VBAT, the battery charger begins constant volt-
age mode. The regulation voltage is factory pro-
grammed to a nominal 4.2V (±0.5%) and will con-
tinue charging until the charging current has
reduced to 10% of the programmed current.
The battery charger will remain in sleep mode,
even if the charger source is disconnected, until
one of the following events occurs: the battery ter-
minal voltage drops below the VRCH threshold; the
charger EN pin is recycled; or the charging source
is reconnected. In all cases, the charger will mon-
itor all parameters and resume charging in the
most appropriate mode.
14
2556.2006.05.1.0
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
