RT/CLK

GND

PVIN

VIN

VSENSE

COMP

SS/TR

EN

PH

BOOT

PWRGD

GND

PVIN

PH

PH

EXPOSED THERMAL

PAD AREA

COMPENSATION

NETWORK

BOOT

CAPACITOR

PVIN

INPUT

BYPASS

CAPACITOR

VOUT

TOPSIDE

GROUND

AREA

VIA toGroundPlane

OUTPUT

INDUCTOR

OUTPUT

FILTER

CAPACITOR

FREQUENCY SET RESISTOR

SLOWSTART

CAPACITOR

ANALOGGROUND TRACE

VIN

INPUT

BYPASS

CAPACITOR

VIN

PVIN

UVLOSET

RESISTORS

FEEDBACK

RESISTORS

EtchUnderComponent

0.010in.Diameter

ThermalVIA toGroundPlane

TPS54521

SLVS981 – JUNE 2010

www.ti.com

capacitor with X5R or X7R dielectric. Make sure to connect this capacitor to the quiet analog ground trace rather

than the power ground trace of the PVIN bypass capacitor. Since the PH connection is the switching node, the

output inductor should be located close to the PH pins, and the area of the PCB conductor minimized to prevent

excessive capacitive coupling. The output filter capacitor ground should use the same power ground trace as the

PVIN input bypass capacitor. Try to minimize this conductor length while maintaining adequate width. The small

signal components should be grounded to the analog ground path as shown. The RT/CLK pin is sensitive to

noise so the RT resistor should be located as close as possible to the IC and routed with minimal lengths of

trace. The additional external components can be placed approximately as shown. It may be possible to obtain

acceptable performance with alternate PCB layouts. However, this layout has been shown to produce good

results and is meant as a guideline.

Figure 57. PCB Layout

Estimated Circuit Area

32

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