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SC417EVB View Datasheet(PDF) - Semtech Corporation

Part Name
Description
MFG CO.
'SC417EVB' PDF : 29 Pages View PDF
SC417/SC427
Applications Information (continued)
Connect the control and switcher power sections as
follows.
Route the VOUT feedback trace in a quiet layer,
away from noise sources.
BST is a noisy node and should be kept as short
as possible. The high-side DH driver uses the
boost capacitor to provide the DH drive current.
The boost capacitor must be placed near the
device and connected to the BST and LX pins
using short, wide traces to minimize
impedance.
Connect the PGND pin on the chip to the V5V
decoupling capacitor and then insert vias
directly to the ground plane.
LDO Section
There are three components for the LDO that need to be
optimized for this layout, the two feedback resistors and
the output capacitor. Use the following guidelines to
locate these components.
The feedback resistors should be placed as close
to the FBL pin as possible. This minimizes the
trace length for the FBL pin.
For the feedback divider connection, the top
resistor must connect directly to the LDO output
capacitor. There should be no PCB inductance
between the top of the resistor divider and the
LDO output capacitor.
If VLDO is not used to power the device, then a
minimum 1.0μF capacitor referenced to AGND is
required.
If VLDO is used to power-up the device by con-
necting it to V5V, then the LDO output capacitor
also becomes the decoupling capacitor for the
V5V input. A minimum 0.1μF capacitor refer-
enced to AGND is required along with a
minimum 1.0μF capacitor referenced to PGND
to filter the gate drive pulses. Each capacitor
should be placed near the V5V pin and con-
nected with short, direct traces. Each capacitor
should connect directly to its respective
ground.
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