ACT5880 datasheet(65/87 Pages) ACTIVE-SEMI

65 / 87 page

ACT5880

Rev 2, 03-Sep-13

- 65 -

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TM and ActivePathTM are trademarks of Active-Semi.

I2CTM is a trademark of NXP.

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this change asserts interrupt to alert the system for

out of regulation.

Component Selection

Each step-down DC/DC regulator utilizes current-

mode

control

and

proprietary

internal

compensation scheme to simultaneously simplify

external

component

selection

and

optimize

transient performance over its full operating range.

No compensation design is required; simply follow a

few simple guidelines described below when

choosing external components.

Inductor Selection

The inductors with inductance 1.5µH to 2.2µH for

REG1 and 1.5µH to 3.3µH for REG2 are

recommended.

Input and Output Capacitor Selection

REG1 and REG2 are designed to operate with

small

22µF~27µF

and

10µF~22µF

output

capacitors respectively, over their output voltage

ranges. The input bypass capacitors sink the quick

component in current, help in suppressing of EMI

and improving the efficiency. Capacitance in range

2μF to 10μF is commonly sufficient. X5R and X7R

dielectrics are recommended for those capacitors

for their suitable and stable characteristics to better

performance.

PCB Layout Considerations

The high frequency element in the inductor current

alternates between the switch ground path and the

input bypass capacitor ground path. Place and

route the two paths close, then place the ground

end of output capacitor close to them, then place

the inductor close is the better order in layout

design. Though the practice is difficult to place all

components close to the ACT5880, it is necessary

to give the step-down DC/DCs the priority for closer

placement.

ACT5880 Datasheet(PDF) 65 Page - Active-Semi, Inc

ACT5880 Datasheet(HTML) 65 Page - Active-Semi, Inc

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