AAT2120 Datasheet, PDF (9/19 Pages) Advanced Analogic Technologies – 500mA Low Noise Step-Down Converter

Functional Block Diagram
FB
VIN
DATA SHEET
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 cur-
rent 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 voltage minus
the R_DS(ON) drop of the P-channel highside MOSFET.
A high-DC gain error amplifier with internal compensa-
tion 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.
Control Loop
The AAT2120 is a 500mA current mode step-down con-
verter. The current through the P-channel MOSFET (high
side) is sensed for current loop control, as well as short-
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
202005A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 24, 2012
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