Ap8801, 500ma led step-down converter, Application information (cont.) – Diodes AP8801 User Manual
Page 7
AP8801
500mA LED STEP-DOWN CONVERTER
AP8801
Document number: DS31765 Rev. 7 - 2
7 of 14
June 2012
© Diodes Incorporated
Application Information (cont.)
The inductor influences the LED current accuracy that the system is able to provide. The following section highlights how to select the
inductor in relation to the device packages and the LED current, while maintaining the chip temperature below 70°C.
0
5
10
15
30
35
40
45
20
25
SUPPLY VOLTAGE (V)
Figure. 16 Minimum Recommended Inductor with 500mA LED Current
12
11
10
9
4
3
2
1
8
7
6
5
NUM
BER o
f
L
E
Ds
47µH
100µH
68µH
47µH
470µH
220µH
150µH
68µH
100µH
150µH
220µH
470µH
8% Accuracy, <70°C Case Temperature
Capacitor Selection
The small size of ceramic capacitors makes them ideal for AP8801 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 AP8801.
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. B1100, with their low forward voltage drop and fast reverse recovery, are the ideal choice for AP8801 applications.