SC417 datasheet(25/29 Pages) SEMTECH

25 / 29 page

SC417/SC427

Applications Information (continued)

PCB Layout Guidelines

The optimum layout for the SC417/SC427 is shown in

Figure 15. The layout highlights the device as a space

saving and high performance solution. This layout shows

an integrated FET buck regulator with a maximum current

of 10A. The total PCB area is approximately 20 x 25 mm.

This figure shows the total area and optimum layout for

the device. If optimum layout is not possible due to PCB

limitations, the following generic guidelines should be

followed.

Generic Layout Guidelines

One or more ground planes are recommended to mini-

mize the effect of switching noise, resistive losses, and to

maximize heat removal. The analog ground reference

AGND should connect directly to the AGND pad and pins.

An AGND plane or island should be used near the device.

All components that are referenced to AGND should

connect directly to this plane and mounted on the IC side

of the PCB.

AGND should connect to PGND (power ground) using an

external zero ohm resistor or using a short PCB trace.

Connect AGND to PGND only at one place, as near to the

AGND and PGND pins as is practical.

Power ground (PGND) should be a separate plane which is

not used for routing analog traces.

All PGND connections should connect directly to the

PGND plane. Indirect connections between AGND and

GND which will create ground loops should be avoided.

The V5V input provides power to the internal analog cir-

cuits and the upper and lower gate drivers. The V5V supply

decoupling capacitors should be tied between V5V and

PGND with short traces.

The switcher power section should be connected directly

to the PGND plane(s) using multiple vias as required for

VOUT Plane

on Top layer

CLDO

CIN

CFF

RFB2

RFB1

RILIM

RLDO2

RLDO1

LX plane on inner

or bottom layer

All components

shown Top Side

AGND plane on

inner layer

VIN plane on inner

or bottom layer

RGND — AGND connects to

PGND close to SC417/SC427

Pin 1 marking

SC417/SC427

with vias for LX,

AGND, VIN

COUT

PGND on inner

or bottom layer

PGND on

Top layer

PGND

Figure 15 — PCB Layout

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