AAT2550
Total Power Solution for Portable Applications
Status monitor output pins are provided to indicate
the battery charge state by directly driving two
Battery Charger
The battery charger is designed to operate with
standard AC adapter input sources, while requiring
a minimum number of external components. It pre-
cisely regulates charge voltage and current for sin-
gle-cell lithium-ion / polymer batteries.
external LEDs. A serial interface output is also
available to report any one of 12 distinct charge
states to the host system microcontroller / micro-
processor. Battery temperature and charge state
are fully monitored for fault conditions. In the event
of an over-voltage or over-temperature condition,
the device will automatically shut down, protecting
the charging device, control system, and the bat-
tery under charge. In addition to internal charge
controller thermal protection, the charger also
offers a temperature sense feedback function (TS
pin) from the battery to shut down the device in the
event the battery exceeds its own thermal limit dur-
ing charging. All fault events are reported to the
user either by simple status LEDs or via the DATA
pin function.
The adapter charge input constant current level
may be programmed up to 1A for rapid charging
applications. The battery charger features thermal
loop charge reduction. In the event of operating
ambient temperatures exceeding the power dissi-
pation abilities of the device package for a given
constant current charge level, the charge control
will enter into thermal regulation. When the system
thermal regulation becomes active, the pro-
grammed constant current charge amplitude will
automatically decrease to a safe level for the pres-
ent operating conditions. If the ambient tempera-
ture drops to a level sufficient to allow the device to
come out of thermal regulation, then the system will
automatically resume charging at the full pro-
grammed constant current level. This intelligent
thermal management system permits the battery
charger to operate and charge a battery cell safely
over a wide range of ambient conditions, while
maximizing the greatest possible charge current
and minimizing the battery charge time for a given
set of conditions.
Charging Operation
As shown in Figure 1, there are four basic modes
for the battery charge cycle:
1. Pre-conditioning / trickle charge
2. Constant current / fast charge
3. Constant voltage
4. End of charge
Preconditioning
(Trickle Charge)
Phase
Constant Current
Phase
Constant Voltage
Phase
Output Charge
Voltage (VCH
)
Preconditioning
Voltage Threshold
(VMIN
)
Regulation
Current
(ICHARGE(REG)
)
Trickle Charge
and Termination
Threshold
Figure 1: Typical Charge Profile.
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2550.2006.07.1.0
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
