AP5724

WHITE LED STEP-UP CONVERTER

AP5724

Document number: DS31843 Rev. 3 - 2

9 of 17

www.diodes.com

July 2010

© Diodes Incorporated

Applications Information

Inductor Selection

A 10

μH~22μH inductor is recommended for most AP5724 applications. For high efficiency the inductor should

have low core losses at 1.2MHz and low DCR (copper wire resistance). The inductor saturation current rating

should also exceed the peak input current, especially for high load current applications (like 3S8P).

Capacitor Selection

The small size of ceramic capacitors are ideal for AP5724 applications. X5R and X7R types are recommended

because they retain their capacitance over wider voltage and temperature ranges than other types such as Y5V

or Z5U. A 1

μF input capacitor and a 1μF output capacitor are sufficient for most AP5724 applications. For high

output current applications like 3S8P, larger output capacitor of 2.2uF ~ 4.7uF is recommended to minimize

output ripple.

Diode Selection

Schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for AP5724

applications. The forward voltage drop of a Schottky diode represents the conduction losses in the diode, while

and diode capacitance need to be considered. Schottky diodes with higher current ratings usually have lower

forward voltage drop and larger diode capacitance, which can cause significant switching losses at the 1.2MHz

switching frequency of the AP5724. Schottky diodes with higher current ratings usually have lower forward

voltage drop and larger diode capacitance. Larger Schottky diode capacitance can cause significant switching

losses at the 1.2MHz switching frequency of the AP5724. A Schottky diode rated at 100mA to 200mA is sufficient

for most AP5724 applications.

LED Current Control

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20

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6.6

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30

3.3