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http://www.union-ic.com Rev.05 Mar.2016

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UM1665

EN

GND

FB

SW

VIN

UM1665

L1

10µH

4.7µF

D1

PWM

50 Hz to 10kHz

D2

30V

(Optional)

82

Ω

1µF

Figure 4. White LED Supply with Adjustable Brightness Control

Using a PWM Signal on the Enable Pin

We also can adjust the white LED brightness using an analog signal on the feedback pin (see

figure 5 below). Add a DC voltage to the FB pin, and adjust the LED current by change the DC

voltage, which control the brightness. The LED current is calculated as:





2

S

1

ADJ

2

1

FB

RS

R

R

R

V

R

R

V

I













EN

GND

FB

SW

VIN

UM1665

L1

10µH

4.7µF

Rs

D1

D2

30V

(Optional)

100nF

R2

R1

Figure 5. White LED Supply with Adjustable Brightness Control

Using an Analog Signal on the Feedback Pin