AIC1896GK Просмотр технического описания (PDF) - Analog Intergrations
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AIC1896GK Datasheet PDF : 15 Pages
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AIC1896
are dimmed by FB pin and turned off completely by
SHDN .
2. Using a DC Voltage
For some applications, the preferred method of a
dimming control uses a variable DC voltage to
adjust LED current. A dimming control using a DC
voltage is shown as Fig. 22. As DC voltage
increases, the voltage drop over R2 increases and
the voltage drop over R1 decreases.
Cautiously selecting R2 and R3 is essential so that
the current from the variable DC source is much
smaller than the LED current and much larger than
the FB pin bias current. With a VDC ranging from
0V to 5V, the selection of resistors in Fig. 22
results in dimming control of LED current from
20mA to 0mA, respectively.
3. Using a Filtered PWM Signal
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.
The circuit is shown in Fig. 23.
VIN
3.3V to 4.2V
C1
4.7µF
L1
10µH D1 SS0540
SLF6025-100M1R0
ZD1
BZV55-B24
U1 AIC1896 23.5V~24.5V
6 IN
LX 1
4
OFF ON
SHDN FB 3
SS GND
5
2
R2
1KΩ
C2
0.033µF
C3
1µF
IOUT=ILED=20mA
R1
62Ω
Fig. 19 White LED Driver with Open-Circuit Protection
PWM
AIC1896
IN
LX
SHDN FB
SS GND
C2
0.033µF
ZD1
R2
Ω 1K
R1
Ω 62
AIC1896
ZD1
IN
LX
R2
SHDN FB
OFF
ON
SS GND
1K
R1
R3
62
30K
C2
0.033µF
PWM
(a)
(b)
Fig. 20 Dimming Control Using a PWM Signal
10
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