AP8802 Diodes, Inc., AP8802 Datasheet - Page 6

• Manufacturer Part Number: AP8802
• Description: 1a Led Step-down Converter
• Manufacturer: Diodes, Inc.

Application Information
LED Current Control
The LED current is controlled by the resistor RSET in Figure 1 connected between V
average output current in the LED(s) is defined as:
If the CTRL pin is driven by an external voltage (lower than 2.5V), the average LED current is:
AP8802 Rev. 3
DS31766
I
I
LED
LED
1200
1000
=
=
800
600
400
200
0
R
V
V
V
0 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 2.25 2.4 2.55 2.7 2.85 3
THD
CTRL
SET
REF
R
V
0.2
0.2
THD
SET
0.33
0.33
0.39
0.39
0.47
0.47
0.47
0.56
0.56
0.68
0.68
0.68 0.82
Figure 3: LED Current setting Vs R
0.82
0.82
1
1
1
LED current Versus RSET and VCTRL
1.2
1.2
RSET value [Ohms]
1.2
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1.5
1.5
1.5
2
2
2
SET
and V
1A LED Step-down Converter
CTRL
IN
3
and SET. The nominal
3
3
©
AP8802
MARCH 2009
Diodes Incorporated
LED current @
VCTRL = 1.25V
LED current @
VCTRL = 2.5V
LED current @
VCTRL = 0.625V