UM1665 Datasheet, PDF (7/15 Pages) Union Semiconductor, Inc. – Low Power DC/DC Boost Converter

V_IN=2.0-6.0V
C_IN
4.7µ F
PWM
50 Hz to 10kHz
UM1665
L1
10µ H
D1
VIN
SW
UM1665
D2
30V
(Optional)
C_OUT
1µ F
EN
FB
GND
R_S
82Ω
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:
  _IRS

V_FB
R₁ R₂  V_ADJ R₁
R_S R ₂
V_IN=2.0-6.0V
L1
10µ H
D1
C_IN
4.7µ F
VIN
SW
UM1665
D2
30V
(Optional)
C_OUT*
100nF
V_FB
EN
FB
GND
R1
Rs
V_ADJ
R2
*A smaller output capacitor value for C_OUT causes a larger LED ripple.
Figure 5. White LED Supply with Adjustable Brightness Control
Using an Analog Signal on the Feedback Pin
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http://www.union-ic.com Rev.05 Mar.2016
7/15