Lithium-Ion/Polymer Battery Charger
Functional Block Diagram
Constant
Current
Charge
Control
CV/
Precharge
1
AAT3687
UVLO
4.2V
BAT
ADPSET
ADP
ADPP#
Voltage
Sense
Current
Compare
Over-
Temperature
Protection
Reverse Blocking
80μA
STAT1
STAT2
DATA
EN
Charge
Status
TS
Window
Comparator
Serial
Data
IC enable
Watchdog
Timer
CT
GND
Functional Description
The AAT3687 is a highly integrated single-cell lithium-
ion/polymer battery charger IC designed to operate
with standard AC adapter input sources, while requir-
ing a minimum number of external components. The
AAT3687 precisely regulates battery charge voltage
and current for 4.2V lithium-ion/polymer battery cells.
The adapter charge input constant current level can
be programmed up to 1.5A for rapid charging appli-
cations. The AAT3687 is rated for operation from -
40°C to +85°C. In the event of operating ambient
temperatures exceeding the power dissipation abili-
ties 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 programmed constant current
charge amplitude will be automatically reduced to a
safe level for the current operating condition. Should
the ambient operating temperature drop below the
thermal loop threshold, the system will automatically
resume charging at the full programmed constant cur-
rent level. This intelligent thermal management sys-
tem permits the AAT3687 to operate and safely
charge a battery cell over a wide range of ambient
conditions while maximizing the greatest possible
charge current for the given set of conditions.
Status monitor output pins are provided to indicate
the battery charge state by directly driving two exter-
nal LEDs. A serial interface output is also available to
report any one of 12 distinct charge states to the sys-
tem microcontroller.
Battery temperature and charge state are fully moni-
tored for fault conditions. In the event of an over-volt-
age or over-temperature failure, the device will auto-
matically shut down, thus protecting the charging
device, control system, and the battery under charge.
In addition to internal charge controller thermal pro-
tection, the AAT3687 also provides 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 during charging. All
fault events are reported to the user either by the sim-
ple status LEDs or via the DATA pin function.
1. Precharge applies to AAT3687 and AAT3687-1 only.
3687.2006.10.1.7
9
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
