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AP8802 Datasheet, PDF (5/13 Pages) Diodes Incorporated – 1A LED Step-Down Converter
AP8802
1A LED Step-Down Converter
Application Information
LED Current Control
The LED current is controlled by the resistor RSET in Figure 2.
Connected between VIN and SET the nominal average output current in the LED(s) is defined as:
ILED
= VTHD
RSET
If the CTRL pin is driven by an external voltage (lower than 2.5V), the average LED current is:
ILED
= VCTRL
VREF
VTHD
RSET
LED current Versus RSET and VCTRL
1200
1000
0.2 0.39
0.47
800
0.56
600
400
200
0
0
0.33
0.68
0.2 0.39
0.82
0.47
1
0.56
1.2
0.33
0.47
0.68
0.82
1
1.2
0.68 0.82 1
1.2
1.5
1.5
1.5
2
2
2
0.15 0.3 0.45 0.6 0.75 0.9 1.05 1.2 1.35 1.5 1.65 1.8 1.95 2.1
33
3
2.25 2.4 2.55 2.7 2.85 3
RSET value [Ohms]
Figure 3: LED Current setting Vs RSET and VCTRL
LED current @
VCTRL = 1.25V
LED current @
VCTRL = 2.5V
LED current @
VCTRL = 0.625V
AP8802 Rev. 1
5 of 13
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MARCH 2009
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