AAT1123 Datasheet, PDF (8/18 Pages) Advanced Analogic Technologies – 1MHz Step-Down Converter

Functional Block Diagram
OUT
DATA SHEET
AAT1123
1MHz Step-Down Converter
VIN
See note
Err
Am. p
Voltage
Reference
EN
INPUT
DH
Logic
DL
LX
PGND
AGND
Note: For adjustable version, the internal feedback divider is omitted and the FB pin is tied directly
to the internal error amplifier.
Functional Description
The AAT1123 is a high performance 600mA 1MHz mono-
lithic step-down converter. It has been designed with the
goal of minimizing external component size and optimiz-
ing efficiency over the complete load range. Apart from
the small bypass input capacitor, only a small L-C filter is
required at the output. Typically, a 4.7μH inductor and a
22μF ceramic capacitor are recommended (see Table of
Values).
The fixed output version requires only three external
power components (C_IN, C_OUT, and L). The adjustable ver-
sion can be programmed with external feedback to any
voltage, ranging from 0.6V to the input voltage. An addi-
tional feed-forward capacitor can also be added to the
external feedback to provide improved transient response
(see Figure 1).
At dropout, the converter duty cycle increases to 100%
and the output voltage tracks the input voltage minus
the R_DSON drop of the P-channel high-side MOSFET.
The input voltage range is 2.7V to 5.5V. The converter
efficiency has been optimized for all load conditions,
ranging from no load to heavy load.
The internal error amplifier and compensation provides
excellent transient response, load, and line regulation.
Soft start eliminates any output voltage overshoot when
the enable or the input voltage is applied.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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201975B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013