AAT3681
USB Port or AC Adapter
Lithium-Ion/Polymer Battery Charger
Functional Block Diagram
Reverse Blocking
ADP
BAT
Current
CV/
Compare
Precharge
UVLO
Charge
Control
Constant
Current
ISET
Over-
Temperature
Protection
Charge
Status
STAT
EN
GND
A status monitor output pin is provided to indicate
the battery charge state by directly driving one
external LED.
Functional Description
The AAT3681 is a high performance battery charg-
er designed to charge single cell lithium-ion/poly-
mer batteries with up to 300mA of current from an
external power source. It is a stand-alone charging
solution, with just one external component required
for complete functionality. The AAT3681 precisely
regulates battery charge voltage and current for
4.2V lithium-ion/polymer battery cells.
Device junction temperature and charge state are
fully monitored for fault conditions. In the event of
an over-voltage or over-temperature failure, the
device will automatically shut down, protecting the
charging device, control system, and the battery
under charge.
The adapter/USB charge input constant current
level can be programmed up to 300mA for rapid
charging applications. The AAT3681 is rated for
operation from -40°C to +85°C. In the event of oper-
ating ambient temperatures exceeding the power
dissipation abilities of the device package for a given
constant current charge level, the charge control will
enter into thermal limit.
Charging Operation
The AAT3681 has four basic modes for the battery
charge cycle: pre-conditioning/trickle charge; con-
stant current/fast charge; constant voltage; and
end of charge (see Figure 1). (AAT3681-1 does not
have trickle charge.)
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3681.2007.01.1.2
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
