MP24830 — 4.5V–90V, PROGRAMABLE FREQUENCY WHITE LED DRIVER

MP24830 Rev. 1.0

www.MonolithicPower.com

13

10/30/2013

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ceramic capacitors with X7R dielectrics with low

ESR and small temperature coefficients.

Select a large-enough capacitor to limit input

of the DC value.

L_ AVG

OUT

IN

SW

IN

IN

OUT

IV

C

fV

(V

V

)











Selecting the Output Capacitor

The output capacitor limits the output voltage

the DC value), and ensures feedback loop

stability.

Use

an

output

capacitor

with

impedance at the switching frequency. Use

ceramic capacitors with low ESR characteristics.

LED

OUT

OUT

SW

OUT

IN

OUT

IV

C

fV

(V

V

)











PC Board Layout

Place the high-current paths (VSS, VDD and

SW) very close to the device with short, direct,

and wide traces. Place the input capacitor as

close as possible to the VDD and VSS pins.

Place the external feedback resistors next to

the FB pin. Keep the switch node traces short

and away from the feedback network.

Pay special attention is required to the

switching frequency loop layout, which should

be as small as possible.

For buck applications, the switching frequency

loop is composed of the input capacitor, the

power MOSFET and the Schottky diode. Place

the Schottky diode close to the power MOSFET

and the input capacitor.

For buck-boost or boost applications, the

switching frequency loop is composed of the

input capacitor, the power MOSFET, the

Schottky diode and the output capacitor. Make

this component loop as small as possible. For

most applications, place the output capacitor

close to the input capacitor and the power

MOSFET.