PRODUCT DATASHEET
AAT2689
TM
SystemPower 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
LX1
Error
Amp
COMP1
Logic
Control
EN1
Logic
20Ω
Voltage
RReeff1
RS1
OS1
Comp
VOCP1
= 0.1V
OT
IN2
OCP
FB_LDO
Error
Amp
VO2
Logic
FB_LDO
Voltage
Ref 2
Control
Logic
EN2
GND
current is sensed through the output inductor DC winding
resistance (DCR). An external resistor network adjusts
the current limit according to the DCR 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 conditions are removed.
Functional Description
The AAT2689 provides two independently regulated DC
outputs; consisting of a high voltage 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 an ideal system-on-a-
chip power solution for consumer communications
equipment.
Channel 2 is a linear low-dropout (LDO) regulator provid-
ing up to 600mA output current at a factory set output
voltage. The device provides extremely low output noise,
low quiescent current and excellent transient response.
Channel 1 is a step-down (Buck) regulator with an input
voltage range 6.0 to 24V; providing up to 2500mA out-
put current. 490kHz fixed switching frequency allows
small L/C filtering components.
The controllers include integrated over-current, soft-
start and over-temperature protection. Independent
input and enable pins provide maximum design flexibil-
ity. The AAT2689 is available in the Pb-free 3x4mm
16-pin TDFN package. The rated operating temperature
range is -40°C to 85°C.
Channel 1 utilizes voltage mode control configured for
optimum performance across the entire output voltage
and load range. The controller includes integrated over-
current, soft-start and over-temperature protection. Over-
w w w . a n a l o g i c t e c h . c o m
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2689.2008.06.1.0
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