PRODUCT DATASHEET
AAT2789
SystemPowerTM
Low Noise, High Frequency Dual Step-Down Converter
Functional Block Diagram
VCC1,2
VP1
OT
OSC
Comp.
FB1
Error
Amp
Logic
LX1
Voltage
Ref 1
Control
Logic
EN1
PGND1
VP2
OT
OSC
Comp.
FB2
EN2
Error
Amp
Voltage
Ref 2
Logic
LX2
Control
Logic
PGND2
AGND1,2
Each of the step-down regulators has an independent
input and enable pin. Adjustable output voltage is pro-
vided. Light load operating mode provides high efficiency
over the entire load range. The enable inputs, when
pulled low, force the respective converter into a low
power non-switching state consuming less than 1μA of
current. Low quiescent current enables excellent life for
battery powered systems.
Functional Description
The AAT2789 is a 2-channel synchronous step-down
(Buck) converter operating from an input voltage range
of 2.7V to 5.5V; making it the ideal choice for single-cell
Lithium-ion/polymer battery powered systems or low
voltage 3.3V and 5V based consumer equipment.
Channel 1 delivers up to 1700mA output current while
Channel 2 delivers up to 800mA. Both converters incor-
porate a unique low noise architecture which reduces
output ripple and spectral noise.
Additional features include integrated soft start to limit
inrush current. Soft start limits the current surge seen at
the input and eliminates output voltage overshoot.
The device utilizes a high switching frequency to mini-
mize external filter sizing. Peak current mode control
eliminates external compensation while optimizing tran-
sient performance and stability.
For overload conditions, the peak input current is limit-
ed. Also, over-temperature protection safeguards the
device from damage due to high operating temperature
or fault conditions. The junction over-temperature
threshold is 140°C with 15°C of hysteresis. Under volt-
age lockout (UVLO) guarantees sufficient input voltage
bias prior to turn-on.
The device requires a minimum of external components
to realize a high efficiency dual-output step-down con-
verter while minimizing solution size and footprint.
The AAT2789 is available in the 3x4mm Pb-free 16-pin
TDFN package and is rated over the -40°C to 85°C oper-
ating temperature range.
w w w . a n a l o g i c t e c h . c o m
2789.2008.03.1.0
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