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SC411

POWER MANAGEMENT

Layout Guidelines

Figure 4: Reference Design

One (or more) ground planes is/are recommended to minimize the effect of switching noise and copper losses, and

maximize heat dissipation. The IC ground reference, VSSA, and the power ground pin, PGND, should both connect

directly to the device thermal pad. The thermal pad should connect to the ground plane(s) using multiple vias.

The VOUT feedback trace must be kept far away from noise sources such as switching nodes, inductors and gate

drives. Route the feedback trace in a quiet layer (if possible) from the output capacitor back to the chip. All compo-

nents should be located adjacent to their respective pins with an emphasis on the chip decoupling capacitors (VCCA

and VDDP) and the components that are shown connecting to VSSA in the above schematic. Make any ground con-

nections simply to the ground plane.

Power sections should connect directly to the ground plane(s) using multiple vias as required for current handling (in-

cluding the chip power ground connections). Power components should be placed to minimize loops and reduce loss-

es. Make all the connections on one side of the PCB using wide copper filled areas if possible. Do not use “minimum”

land patterns for power components. Minimize trace lengths between the gate drivers and the gates of the MOSFETs

to reduce parasitic impedances (and MOSFET switching losses), the low-side MOSFET is most critical. Maintain a

length to width ratio of <20:1 for gate drive signals. Use multiple vias as required by current handling requirements

(and to reduce parasitics) if routed on more than one layer. Current sense connections must always be made using

Kelvin connections to ensure an accurate signal, with the current limit resistor located at the device.

We will examine the reference design used in the Design Procedure section while explaining the layout guidelines in

more detail.

VOUT

C8

1nF

VBAT

R1

1M

PGOOD

Q1

IRF7811AV

C10

1uF

R4 7k87

C1 0u1

D1

C2

2n2/50V

VBAT

5VSUS

L1

2u2

+

C6

220u/25m

VOUT

R2

10R

5VSUS

VOUT

1

VCCA

2

FB

3

PGD

4

VDDP

9

ILIM

10

LX

11

DH

12

U1

SC411

Q2

FDS6676S

C5

56p

0402

0402

0402

0402

0402

0402

0603

0603

0402

0603

SOD323

0402

C3

0u1/25V

0603

C4

10u/25V

1210

+

C7

220u/25m

VBAT = 8V to 20V

VOUT = 1.2V @ 6A

7343

7343

C9

1uF

R3

20k0

R5

14k3