AAT2138 Datasheet, PDF (15/18 Pages) Skyworks Solutions Inc. – High Current Step-Down Converter with High-Precision Programmable Current Limited Load Switch

DATA SHEET
AAT2138
High Current Step-Down Converter
with High-Precision Programmable Current Limited Load Switch
Printed Circuit Board
Layout Recommendations
For best performance of the AAT2138, the following
guidelines should be followed when designing the PCB
layout:
1. Reliably solder the exposed pad (EP) to the GND
plane. A GND pad below EP is strongly recommended.
2. Keep the power traces, including the GND trace, the
SW trace and the SYSIN, REGIN short, direct and wide
to allow large current flow. Keep the L connection to
the SW pins as short as possible. Do not put any sig-
nal lines under the inductor.
3. Connect the input capacitors (C1 and C21) as close as
possible between SYSIN and REGIN and GND to get
good power filtering.
4. Connect the input capacitor C23 as close as possible
between REGIN and AGND to get good power filtering
and load regulation.
5. Keep the switching node, SW away from the sensitive
FB node.
6. Separate the feedback trace from any power trace and
connect as close as possible to the load point. Sensing
along a high-current load trace will degrade DC load
regulation. Place external feedback resistors as close
as possible to the FB pin to minimize the length of the
high impedance feedback trace.
7. Minimize the resistance of the trace from the load
return to GND. This will help minimize any error in DC
regulation due to differences in the potential of the
internal signal ground and the power ground.
VOUT
3.4V
SW
C32
Option
C31
22μF ^R1
274K
L1
1uH
C4
22pF
RSET
R2
59K
U1
AAT2138
13
14
9
6
1
2
SW
SW
FB
RSET
PGND
7 ^PGND
AGND
REGIN
REGIN
SYSIN
SYSIN
ENREG
3
4
11
12
5
8
ENSYS ₁₀
MODE
C21
10μF
C22
680μF
C23
0.1μF
REGIN
GND
C1
1μF
SYSIN
2.7V-5.5V
GND
GND
J3
J2
J1
SYSIN
GND SYSIN
GND SYSIN
GND
Figure 3. AAT2138 Evaluation Board Schematic.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
202006C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
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