ACT8796_08 datasheet(33/34 Pages) ACTIVE-SEMI

33 / 34 page

LOW-DROPOUT LINEAR REGULATORS

ACT8796

Rev1, 10-Oct-08

Innovative Power

- 33 -

www.active-semi.com

ActivePMU

TM is a trademark of Active-Semi.

2CTM is a trademark of Philips Electronics.

PCB Layout Considerations

PCB Layout Considerations The ACT8796’s LDOs

provide good DC, AC, and noise performance over

a wide range of operating conditions, and are rela-

tively insensitive to layout considerations. When

designing a PCB, however, careful layout is neces-

sary to prevent other circuitry from degrading LDO

performance.

A good design places input and output capacitors

as close to the LDO inputs and output as possible,

and utilizes a star-ground configuration for all regu-

lators to prevent noise-coupling through ground.

Output traces should be routed to avoid close prox-

imity to noisy nodes, particularly the SW nodes of

the DC/DCs.

REFBP is a filtered reference noise, and internally

has a direct connection to the linear regulator con-

troller. Any noise injected onto REFBP will directly

affect the outputs of the linear regulators, and there-

fore special care should be taken to ensure that no

noise is injected to the outputs via REFBP. As with

the LDO output capacitors, the REFBP bypass ca-

pacitor should be placed as close to the IC as pos-

sible, with short, direct connections to the star-

ground. Avoid the use of via whenever possible.

Noisy nodes, such as from the DC/DCs, should be

routed as far away from REFBP as possible.

FUNCTIONAL DESCRIPTION (CONT’D)

ACT8796 Arkusz danych(PDF) 33 Page - Active-Semi, Inc