PRODUCT DATASHEET
AAT2688
TM
SystemPower
4.5A PMIC Solution for 12V Adapter Systems with 2-Output High Performance Step-Down Converters
Functional Block Diagram
VINT
Reg.
OT
VL1
IN1
OSC
Comp..
Comp
FB1
BST1
Error
Amp
30mΩ
COMP1
Logic
LX1
Control
Logic
EN 1
Voltage
Ref
20Ω
PGND
GND1
DL1
RS1
OS1
Comp
OT
IN2
OCP
FB_LDO
Error
Amp
OUT2
Logic
FB_LDO
Voltage
Ref 2
Control
Logic
EN2
GND2
winding resistance. An external resistor network adjusts
the current limit according to the DC winding resistance
of the desired inductor and the desired output current
limit. Frequency reduction limits over-current stresses
during short-circuit events. The operating frequency
returns to the nominal setting when over-current condi-
tions are removed.
Functional Description
The AAT2688 provides two independently regulated DC
outputs; consisting of a high voltage synchronous step-
down (Buck) regulator and a low input voltage linear low
dropout (LDO) regulator. The PMIC is optimized for low
cost 12V adapter inputs, making the device the ideal
system-on-a-chip power solution for consumer commu-
nications equipment.
Channel 2 is a low-dropout (LDO) regulator providing up
to 600mA output current at a factory set output voltage.
The device provides low output noise, low quiescent cur-
rent, and excellent transient response.
Channel 1 is a step-down (Buck) regulator with an input
voltage range 6.0 to 24V; providing up to 4.5A output
current. 490kHz fixed switching frequency allows small
L/C filtering components.
The regulators include integrated over-current, soft-start
and over-temperature protection. Independent input and
enable pins provide maximum design flexibility.
Channel 1 utilizes voltage mode control configured for
optimum performance across the entire output voltage
and load range. The regulator includes integrated over-
current, soft-start and over-temperature protection.
Over-current is sensed through the output inductor DC
The AAT2688 is available in the Pb-free 4x5 mm 24-pin
TQFN package. The rated operating temperature range is
-40°C to 85°C.
w w w . a n a l o g i c t e c h . c o m
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2688.2008.06.1.0
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