SC220(2012) 데이터 시트보기 (PDF) - Semtech Corporation
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SC220 Datasheet PDF : 14 Pages
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SC220
Applications Information (Cont.)
PCB Layout Considerations
PCB Layout is important in designing a switching regula-
tor. A few fundamental layout considerations will help to
achieve the specified performance. Poor layout can
degrade the performance of the switching regulator and
may contribute to EMI problems, ground bounce, and
possibly poor regulation and instability.
The following guidelines are recommended when devel-
oping a PCB layout:
1. The input capacitor, CIN should be placed as close to
the PVIN and PGND pins as possible. This capacitor
provides a low impedance loop for the pulsed
currents present at the buck converter’s input. Use
short wide traces to connect this capacitor as close
to the IC as possible. This will minimize EMI and input
voltage ripple by localizing the high frequency current
pulses.
2. Keep the SW pin traces as short as possible to minimize
the pickup of high frequency switching edges to
other parts of the circuit. The output capacitor, C
OUT
and the inductor should be put as close as possible to
the related pins of the IC, and connected as close as
possible between the SW and ground pins.
3. Route the output voltage feedback/sense path
from the output capacitor path, and away from the
inductor and SW node to minimize the possible noise
and magnetic interference to the output feedback/
sense path.
4. Use a ground plane referenced to the PGND pin,
and the ground connection of the input and output
capacitors should be put on this plane and close to
each other if possible, and as close to the PGND pin as
possible. Use several vias to connect to the component
side ground to further reduce noise and interference
on sensitive circuit nodes.
5. If possible, minimize the resistance from the VOUT
and AGND pins to the load. This will reduce the
voltage drop on the ground plane and improve the
load regulation. And it will also improve the overall
efficiency by reducing the copper losses on the output
and ground planes.
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