AP8802

1A LED Step-down Converter

AP8802 Rev. 5

10 of 16

DECEMBER 2009

DS31766

www.diodes.com

Capacitor Selection

The small size of ceramic capacitors makes them ideal for AP8802 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 2.2

μF input capacitor is sufficient for most intended applications of AP8802.

A 4.7

μF input capacitor is suggested for application with an input voltage equal or higher than 40V.

Diode Selection

Schottky diodes, e.g. B2100 or B1100, with their low forward voltage drop and fast reverse recovery, are the

ideal choice for AP8802 applications.

PWM Dimming

A Pulse Width Modulated (PWM) signal with a max resolution of 8bit, can be applied to the CTRL pin to

change the output current to a value above or below the nominal average value set by resistor RSET. To

achieve this resolution the PWM frequency has to be lower than 500Hz.

Thermal Considerations

The graph below in figure 8, gives details for power derating. This assumes the device to be mounted on a

25x25mm PCB with 1oz copper standing in still air.

Maximum Power Dissipation

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

0

25

50

75

100

125

Ambient Temperature (Deg C)

SOP-8L

SOP-8L - EP

DFN3030-10

Figure 8: AP8802 derating curves

Package Selection

The device comes with a wide selection of packages. The suggested package is able to provide a case

temperature below 70˚C (with an ambient temperature of 25˚C) for the combination of input voltage and load

requested.