AAT2120 Datasheet, PDF (9/20 Pages) Advanced Analogic Technologies – 500mA Low Noise Step-Down Converter

Functional Block Diagram
FB
VIN
AAT2120
500mA Low Noise Step-Down Converter
VP
Err
Amp
Voltage
Reference
EN
INPUT
DH
Logic
LX
DL
GND
PGND
Functional Description
The AAT2120 is a high performance 500mA,
1.8MHz monolithic step-down converter designed
to operate with an input voltage range of 2.7V to
5.5V. The converter operates at 1.8MHz, which
minimizes the size of external components. Typical
values are 3.3µH for the output inductor and 4.7µF
for the ceramic output capacitor.
The device is designed to operate with an output
voltage as low as 0.6V. Power devices are sized for
500mA current capability while maintaining over
90% efficiency at full load. Low current efficiency is
maintained at greater than 80% down to 1mA of
load current.
At dropout, the converter duty cycle increases to
100% and the output voltage tracks the input volt-
age minus the R_DS(ON) drop of the P-channel high-
side MOSFET.
A high-DC gain error amplifier with internal com-
pensation controls the output. It provides excellent
transient response and load/line regulation. Soft
start eliminates any output voltage overshoot when
the enable or the input voltage is applied.
2120.2007.10.1.1
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