Diodes AP8800 Manuel d'utilisateur télécharger pdf (Page 5)

AP8800

Document number: DS31764 Rev. 7 - 2

5 of 13

www.diodes.com

August 2012

P8800

Application Information (cont.)

Inductor Selection

A 100μH inductor is recommended for most AP8800 applications with input voltage at 24V.

Figure 3 displays the resulting switching frequency varying the main circuit parameters: Supply voltage, Inductor value and number of LEDs to be

driven.

Switching Frequency

100

470

100

150

470

150

220

100

200

300

400

500

600

700

0 50 100 150 200 250 300 350 400 450 500

Inductor Value [uH]

Frequency [kHz]

12V - 1LED

24V - 3 LEDs

28V - 4LEDs

Figure 3 Switching Frequency vs. Supply Voltage, Inductor, and Number of LEDs

Capacitor Selection

The small size of ceramic capacitors makes them ideal for AP8800 applications. X5R and X7R types are recommended because they retain their

capacitance over wider voltage and temperature ranges than other types such as Z5U. A 1μF input capacitor is sufficient for most intended

applications of AP8800.

Diode Selection

Schottky diode, e.g. B140, with their low forward voltage drop and fast reverse recovery, is the ideal choice for AP8800 applications.

Miscellaneous

To ensure optimal performance, RSVD pin should be connected to the GND pin with the shortest trace length.

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Diodes AP8800 Manuel d'utilisateur Page 5