PRODUCT DATASHEET
AAT3688
BatteryManager
TM
Functional Block Diagram
Reverse Blocking
USB Port Lithium-Ion/Polymer Battery Charger
USB
USBSEL
USBH
USBL
CHR
Charge
Reduction
Loop
BAT
Current
Compare
CV/
Precharge
Constant
Current
Charge
Control
UVLO
Over-
Temperature
Protect
STAT1
STAT2
Charge
Status
80μA
DATA
Serial
Data
TS
Window
Comparator
IC enable
EN
GND
Functional Description
The AAT3688 is a highly integrated single cell lithium-
ion/polymer battery charger IC designed to operate from
USB port V
BUS
supplies, while requiring a minimum num-
ber of external components. The device precisely regu-
lates battery charge voltage and current for 4.2V lithi-
um-ion/polymer battery cells.
The AAT3688 is specifically designed to be powered from
a USB port V
BUS
supply, but it can also be powered from
any input voltage source capable supplying 4.5V to 5.5V
for loads up to 500mA. Depending on the USB port type,
the AAT3688 constant charge current can be externally
programmed for two levels, USB high and USB low, for
maximum constant current charge levels up to 500mA.
Typically, the USB charge levels are set at 500mA and
100mA for the USBH and USBL modes; however, the
user may program either mode to any level they desire
below 500mA. The USBH/L mode has an automatic
Charge Reduction Loop control to allow users to charge
the battery with limited available current from a USB
port while maintaining the regulated port voltage. This
system assures the battery charge function will not over-
load a USB 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 moni-
tored for fault conditions. In the event of an over-voltage
or over-temperature failure, the device will automati-
cally shut down, thus protecting the charging device,
control system, and the battery under charge. In addi-
tion to internal charge controller thermal protection, the
AAT3688 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.
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