AP5725WG-7 Diodes Inc, AP5725WG-7 Datasheet - Page 11

• Manufacturer Part Number: AP5725WG-7
• Description: Switching Converters, Regulators & Controllers WH LED STEP-UP DC/DC CONV 2-6 LED
• Manufacturer: Diodes Inc

Specifications of AP5725WG-7

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Applications Information
2. Using a DC Voltage
For some applications, the preferred method of brightness control is a variable DC voltage to adjust the
LED current. The dimming control using a DC voltage is shown in Figure 3. As the DC voltage increases, the
voltage drop on R2 increases and the voltage drop on R
selection of R2 and R3 will make the current from the variable DC source much smaller than the LED current and
much larger than the FB pin bias current. For V
dimming control of LED current from 0mA to 20mA.
3. Using a Filtered PWM Signal
The filtered PWM signal can be considered as an adjustable DC voltage. It can be used to replace the variable
DC voltage source in dimming control.
4. Using a Logic Signal
For applications that need to adjust the LED current in discrete steps, a logic signal can be used as shown in
Figure 4. R
increases when the NMOS is turned on.
AP5725
Document number: DS31844 Rev. 3 - 2
SET
sets the minimum LED current (when the NMOS is off). R
Figure 4. Dimming Control Using a Logic Signal
Figure 3. Dimming Control Using a DC Voltage
(Continued)
Signal
Logic
V
DC
100k
DC
R3
R
AP5725
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range from 0V to 2V, the selection of resistors in Figure 3 gives
INC
FB
AP5725
11 of 17
FB
R2
5k
SET
decreases. Thus, the LED current decreases. The
R
12
WHITE LED STEP-UP CONVERTER
SET
R
SET
SET
sets how much the LED current
AP5725
© Diodes Incorporated
July 2010