SC4626CEVB-1 View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
'SC4626CEVB-1' PDF : 21 Pages View PDF
Applications Information (continued)
PCB Layout Considerations
The layout diagram in Figure 4 shows a recommended PCB
top-layer and bottom layer for the SC4626 and supporting
components. Fundamental layout rules must be followed
since the layout is critical for achieving the performance
specified in the Electrical Characteristics table. Poor layout
can degrade the performance of the DC-DC converter
and can contribute to EMI problems, ground bounce, and
resistive voltage losses. Poor regulation and instability
can result.
The following guidelines are recommended when
developing a PCB layout:
1. The input capacitor, CIN should be placed as close to the
VIN and GND 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 as closely to the IC as possible. This will
minimize EMI and input voltage ripple by localizing
the high frequency current pulses.
2. Keep the LX pin traces as short as possible to minimize
pickup of high frequency switching edges to other
parts of the circuit. COUT and L should be connected as
close as possible between the LX and GND pins, with
a direct return to the GND pin from COUT.
3. Route the output voltage feedback/sense path away
from inductor and LX node to minimize noise and
magnetic interference.
4. Use a ground plane referenced to the SC4626 GND
pin. 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
GND 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.
SC4626
L
VOUT
CIN
COUT
U1
VIN
GND
(a) Top layer
GND
EN
(b) Bottom layer
Figure 4 — Recommended PCB
Top & Bottom Layer Layout
© 2009 Semtech Corp.
20
www.semtech.com
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