AAT1147 Datasheet, PDF (14/18 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
Layout
The suggested PCB layout for the AAT1147 is shown in
Figures 2, 3, and 4. The following guidelines should be
used to help ensure a proper layout.
1. The input capacitor (C2) should connect as closely as
possible to V_IN (Pin 3) and PGND (Pins 6-8).
2. C1 and L1 should be connected as closely as possi-
ble. The connection of L1 to the LX pin should be as
short as possible.
3. The feedback trace or OUT pin (Pin 2) should be
separate from any power trace and connect as close-
ly as possible to the load point. Sensing along a
high-current load trace will degrade DC load regula-
tion. External feedback resistors should be placed as
closely as possible to the OUT pin (Pin 2) to minimize
the length of the high impedance feedback trace.
4. The resistance of the trace from the load return to
the PGND (Pins 6-8) should be kept to a minimum.
This will help to minimize any error in DC regulation
due to differences in the potential of the internal
signal ground and the power ground.
A high density, small footprint layout can be achieved
using an inexpensive, miniature, non-shielded, high DCR
inductor. An evaluation board is available with this induc-
tor and is shown in Figure 6. The total solution footprint
area is 40mm².
Figure 6: Minimum Footprint Evaluation Board
Using 2.0mm x 1.6mm x 0.95mm Inductor.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
14
201986A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 23, 2012