ACT5880 datasheet(70/87 Pages) ACTIVE-SEMI

70 / 87 page

ACT5880

Rev 2, 03-Sep-13

- 70 -

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PCB Layout Considerations

PCB Layout Considerations The ACT5880’s LDOs

provide good DC, AC, and noise performance over

a wide range of operating conditions, and are

relatively insensitive to layout considerations. When

designing a PCB, however, careful layout is

necessary 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

regulators

prevent

noise-coupling

through

ground. Output traces should be routed to avoid

close proximity 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

controller. Any noise injected onto REFBP will

directly affect the outputs of the linear regulators,

and therefore 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 capacitor should be placed as close

to the IC as possible, 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.

ACT5880 датащи(PDF) 70 Page - Active-Semi, Inc