AAT2556 Datasheet, PDF (12/27 Pages) Advanced Analogic Technologies – Battery Charger and Step-Down Converter for Portable Applications

DATA SHEET
AAT2556
Battery Charger and Step-Down Converter for Portable Applications
Functional Block Diagram
ADP
Reverse Blocking
BAT
ISET
STAT
Constant
Current
Over-
Temperature
Protection
Charge
Control
UVLO
VREF
EN_BAT
VIN
FB
EN_BUCK
-
+
VREF
Input
DH
LX
Logic
DL
GND
Functional Description
The AAT2556 is a high performance power system com-
prised of a 500mA lithium-ion/polymer battery charger
and a 250mA step-down converter.
The battery charger is designed for single-cell lithium-ion/
polymer batteries using a constant current and constant
voltage algorithm. The battery charger operates from the
adapter/USB input voltage range from 4V to 6.5V. The
adapter/USB charging current level can be programmed
up to 500mA for rapid charging applications. A status
monitor output pin is provided to indicate the battery
charge state by directly driving one external LED. Internal
device temperature and charging state are fully moni-
tored 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 sys-
tem, and the battery under charge. Other features include
an integrated reverse blocking diode and sense resistor.
The step-down converter operates with an input voltage
of 2.7V to 5.5V. The switching frequency is 1.5MHz,
minimizing the size of the inductor. Under light load con-
ditions, the device enters power-saving mode; the
switching frequency is reduced, and the converter con-
sumes 30μA of current, making it ideal for battery-oper-
ated applications. The output voltage is programmable
from V_IN to as low as 0.6V. Power devices are sized for
250mA current capability while maintaining over 90%
efficiency at full load. Light load efficiency is maintained
at greater than 80% down to 1mA of load current. A
high-DC gain error amplifier with internal compensation
controls the output. It provides excellent transient
response and load/line regulation.
Under-Voltage Lockout
The AAT2556 has internal circuits for UVLO and power on
reset features. If the ADP supply voltage drops below the
UVLO threshold, the battery charger will suspend charg-
ing and shut down. When power is reapplied to the ADP
pin or the UVLO condition recovers, the system charge
control will automatically resume charging in the appro-
priate mode for the condition of the battery. If the input
voltage of the step-down converter drops below UVLO,
the internal circuit will shut down.
Protection Circuitry
Over-Voltage Protection
An over-voltage protection event is defined as a condition
where the voltage on the BAT pin exceeds the over-volt-
age protection threshold (V_OVP). If this over-voltage condi-
tion occurs, the charger control circuitry will shut down
the device. The charger will resume normal charging
operation after the over-voltage condition is removed.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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202177B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013