AAT1147 Datasheet, PDF (8/18 Pages) Advanced Analogic Technologies – High Efficiency, Low Noise, Fast Transient 400mA Step-Down Converter

DATA SHEET
AAT1147
High Efficiency, Low Noise, Fast Transient 400mA Step-Down Converter
Functional Block Diagram
OUT
VIN
Err
Am. p
Voltage
Reference
EN
INPUT
DH
Logic
DL
LX
PGND
AGND
Functional Description
The AAT1147 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 at heavy load. 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 recommended (see table of val-
ues).
Only three external power components (C_IN, C_OUT, and L)
are required. Output voltage is programmed with exter-
nal resistors and ranges from 0.6V to the input voltage.
An additional 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_DS(ON) 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 heavy load conditions
up to 400mA.
The internal error amplifier and compensation provide
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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201986A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 23, 2012