SC121 datasheet(20/23 Pages) SEMTECH

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SC121

GND

VIN

CIN

SC121

nd layer)

OUT

GND

7.0mm

5.2mm

CFB

VOUT

COUT

Figure 4 — Layout Drawing

PCB Layout Considerations

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 simple design rules can be implemented to

ensure good layout:

Place the inductor and filter capacitors as close

to the device as possible and use short wide

traces between the power components.

Route the output voltage feedback path away

from the inductor and LX node to minimize

noise and magnetic interference.

•

Maximize ground metal on the component side

to improve the return connection and thermal

dissipation. Separation between the LX node

and GND should be maintained to avoid cou-

pling capacitance between the LX node and the

ground plane.

Use a ground plane with several vias connecting

to the component side ground to further reduce

noise interference on sensitive circuit nodes.

A suggested layout is shown in Figure 4.

•

Applications Information (continued)

SC121 Datasheet(PDF) 20 Page - Semtech Corporation