AP3039 查看數據表（PDF） - BCD Semiconductor

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AP3039

BOOST CONTROLLER

BCD Semiconductor 

Data Sheet

BOOST CONTROLLER

Typical Application (Continued)

AP3039

Note 2: The output voltage is decided by R5, R6 and the internal 0.5V reference. The output voltage accuracy is

determined by the accuracy of R5 and R6, for which the precise resistors are preferred.

VOUT= 0.5V * (R5 + R6)

R6

Note 3: In this application, the LED current is controlled by the feedback resistor R5. LEDs current accuracy is

determined by regulator‘s feedback threshold accuracy and is independent of the LEDs‘ forward voltage variation.

So the precise resistors are the better choices. The resistance of R5 is in inverse proportion to the LED current

since the feedback reference is fixed at 0.5V. The relation of R5 and the LED current can be expressed as below:

0.5V

R5=

ILED

Note 4: The summation of LED current is determined by R5 and internal 0.5V reference same as the illustration in

Figure 22.

More detailed application information please refer to application note.

Dec. 2009 Rev. 1. 4

BCD Semiconductor Manufacturing Limited

16

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