AP8802_0912 Datasheet, PDF (10/16 Pages) Diodes Incorporated – 1A LED Step-down Converter

AP8802
1A LED Step-down Converter
Application Information (Continued)
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 2.2μF input capacitor is sufficient for most intended applications of AP8802.
A 4.7μF 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
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
DFN3030-10
SOP-8L - EP
SOP-8L
25
50
75
100
125
Ambient Temperature (Deg C)
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.
AP8802 Rev. 5
DS31766
10 of 16
www.diodes.com
DECEMBER 2009
© Diodes Incorporated