AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
Functional Block Diagram
Reverse Blocking
USB
USBSEL
USBH
BAT
Current
Compare
CV/
Precharge
USBL
Charge
Reduction
Loop
CHR
Charge
Control
UVLO
Constant
Current
Over-
Temperature
Protect
STAT1
STAT2
Charge
Status
80µA
TS
Serial
Data
DATA
EN
Window
Comparator
IC enable
GND
maintaining the regulated port voltage. This sys-
tem assures the battery charge function will not
overload a USB port while charging if other system
demands also share power with the respective port
supply.
Functional Description
The AAT3688 is a highly integrated single cell lithi-
um-ion/polymer battery charger IC designed to
operate from USB port VBUS supplies, while requir-
ing a minimum number of external components.
The device precisely regulates battery charge volt-
age and current for 4.2V lithium-ion/polymer bat-
tery cells.
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.
The AAT3688 is specifically designed to be pow-
ered from a USB port VBUS 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 pro-
grammed 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
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 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.
10
3688.2006.10.1.5
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
