AAT1146 Datasheet, PDF (9/20 Pages) Advanced Analogic Technologies – Fast Transient 400mA Step-Down Converter

Functional Block Diagram
DATA SHEET
AAT1146
Fast Transient 400mA Step-Down Converter
OUT
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 OUT pin is tied directly
to the internal error amplifier.
Functional Description
The AAT1146 is a high performance 400mA 1.4MHz
monolithic step-down converter. It has been designed
with the goal of minimizing external component size and
optimizing 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 4.7μF ceramic capacitor are recommend-
ed (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 (C_FF) 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 400mA.
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
201985B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
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