AAT2786 Datasheet, PDF (21/27 Pages) Advanced Analogic Technologies – 1.5A Step-Down Converter and 150mA LDO

SystemPower^TM
PRODUCT DATASHEET
AAT2786
1.5A Step-Down Converter and 150mA LDO
PCB Layout
The suggested PCB layout for the AAT2786 is shown in
Figures 1 and 2. The following guidelines should be used
to help ensure a proper layout.
1. The input and output capacitors (C2, C6, and C7)
should connect as closely as possible to the input and
output pins.
2. R1 and C3 are optional low pass filter components
for the IN supply pin for the BUCK if additional noise
decupling is required in a noisy system.
3. The connection of L1 to the LX pin should be as short
as possible.
4. The feedback trace or FB pin should be separated
from any power trace and connect as closely as pos-
sible to the load point. Sensing along a high-current
load trace will degrade DC load regulation.
5. The resistance of the trace from the load return to
PGND should be kept to a minimum. This will help to
minimize any error in DC regulation due to differ-
ences in the potential of the internal signal ground
and the power ground.
6. Connect unused signal pins to ground to avoid
unwanted noise coupling.
7. For low output noise and highest possible power sup-
ply ripple rejection performance, it is critical to con-
nect the bypass capacitor (C8) and output capacitor
(C7) directly to the LDO regulator ground pin. This
method will eliminate any load noise or ripple current
feedback through the LDO regulator.
8. For good thermal coupling, PCB vias are required
from the pad for the TDFN paddle to the bottom
ground plane.
2786.2008.04.1.0
www.analogictech.com
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