AAT3685 AAT, AAT3685 Datasheet - Page 10

• Manufacturer Part Number: AAT3685
• Description: Lithium-Ion/Polymer Battery Charger
• Manufacturer: AAT

Functional Block Diagram
Functional Description
The AAT3685 is a highly integrated single cell lithi-
um-ion/polymer battery charger IC designed to
operate from adapter or USB port V
while requiring a minimum number of external
components. The device precisely regulates bat-
tery charge voltage and current for 4.2V lithium-
ion/polymer battery cells.
The AAT3685 is specifically designed for being
powered from a USB port V
also be powered from any input voltage source
capable supplying 4.5V to 5.5V for loads up to 1A.
The AAT3685 constant charge current can be
externally programmed for two levels, SETH and
SETL, for maximum constant current charge levels
up to 1A. The SETH/L mode has an automatic
Charge Reduction Loop control to allow users to
charge the battery with limited available current
from a port while maintaining the regulated port
voltage. This system assures the battery charge
10
ADP/USB
PWRSEL
STAT1
STAT2
DATA
SETH
SETL
CHR
EN
BUS
supply, but it can
Reduction
Charge
BUS
Loop
supplies,
Charge
Status
Serial
Data
Constant
Compare
Current
Current
IC enable
Lithium-Ion/Polymer Battery Charger
function will not overload the port while charging if
other system demands also share power with the
respective port supply.
Status monitor output pins are provided to indicate
the battery charge status by directly driving two
external LEDs. A serial interface output is available
to report 14 various charge states to a system
microcontroller.
Battery 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, thus protecting
the charging device, control system, and the bat-
tery under charge. In addition to internal charge
controller thermal protection, the AAT3685 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 simple status LEDs or via the
DATA pin function.
Control
Charge
Reverse Blocking
Window
Comparator
GND
Temperature
Precharge
Protect
UVLO
Over-
CV/
80μA
BAT
TS
AAT3685
3685.2006.10.1.3