ACT8828 datasheet(30/49 Pages) ACTIVE-SEMI

30 / 49 page

STEP-DOWN DC/DC CONVERTERS

ACT8828

Rev 3, 24-Sep-09

Active-Semi

Innovative Power

- 30 -

www.active-semi.com

ActivePMU

TM and ActivePathTM are trademarks of Active-Semi.

2CTM is a trademark of Philips Electronics.

FUNCTIONAL DESCRIPTION CONT’D

between two sets of voltages, such as to implement

'normal' and 'standby' modes in a system utilizing

the ACT8828 to implement an advanced power

management architecture.

PCB Layout Considerations

High switching frequencies and large peak currents

make PC board layout an important part of step-

down DC/DC converter design. A good design

minimizes excessive EMI on the feedback paths

and voltage gradients in the ground plane, both of

which can result in instability or regulation errors.

Step-down DC/DCs exhibit discontinuous input

current, so the input capacitors should be placed as

close as possible to the IC, and avoiding the use of

vias if possible. The inductor, input filter capacitor,

and output filter capacitor should be connected as

close together as possible, with short, direct, and

wide traces. The ground nodes for each regulator’s

power loop should be connected at a single point in

a star-ground configuration, and this point should

be connected to the backside ground plane with

multiple vias. The output node for each regulator

should be connected to its corresponding OUTx pin

through the shortest possible route, while keeping

sufficient distance from switching nodes to prevent

noise injection. Finally, the exposed pad should be

directly connected to the backside ground plane

using multiple vias to achieve low electrical and

thermal resistance.

ACT8828 Datasheet(PDF) 30 Page - Active-Semi, Inc