AAT1162
12V, 1.5A Step-Down DC/DC Converter
Max DCR
(mΩ)
Rated DC
Size WxLxH
(mm)
Manufacturer
Part Number
L (µH)
Current (A)
Sumida
Sumida
Coilcraft
CDRH103RNP-2R2N
CDR7D43MNNP-3R7NC
MSS1038-382NL
2.2
3.7
3.8
16.9
18.9
13
5.10
4.3
4.25
10.3x10.5x3.1
7.6x7.6x4.5
10.2x7.7x3.8
Table 2: Typical Surface Mount Inductors.
4. The input capacitors (C9 and C1) should be
connected as close as possible to IN (Pins 4 and
5) and DGND (Pin 6) to get good power filtering.
5. Keep the switching node LX away from the
sensitive FB node.
6. The feedback trace for the FB pin should be
separate from any power trace and connected
as closely as possible to the load point.
Sensing along a high-current load trace will
degrade DC load regulation. The feedback
resistors should be placed as close as possible
to the FB pin (Pin 9) to minimize the length of
the high impedance feedback trace.
7. The output capacitors C3, 4, and 5 and L1
should be connected as close as possible and
there should not be any signal lines under the
inductor.
8. The resistance of the trace from the load return
to the PGND (Pin 16) should be kept to a min-
imum. This will help to minimize any error in
DC regulation due to differences in the poten-
tial of the internal signal ground and the power
ground.
Layout Guidance
Figure 2 is the schematic for the evaluation board.
When laying out the PC board, the following layout
guideline should be followed to ensure proper
operation of the AAT1162:
1. Exposed pad EP1 must be reliably soldered to
PGND/DGND/AGND. The exposed thermal
pad should be connected to board ground
plane and pins 6, 11, 13, 14 and 16. The ground
plane should include a large exposed copper
pad under the package for thermal dissipation.
2. The power traces, including GND traces, the
LX traces and the VIN trace should be kept
short, direct and wide to allow large current
flow. The L1 connection to the LX pins should
be as short as possible. Use several via pads
when routing between layers.
3. Exposed pad pin EP2 must be reliably sol-
dered to the LX pins 1 and 2. The exposed
thermal pad should be connected to the board
LX connection and the inductor L1 and also
pins 1 and 2. The LX plane should include a
large exposed copper pad under the package
for thermal dissipation.
1162.2007.09.1.2
13
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
