Agamem Microelectronics Inc.
PRELIMINARY
■
TYPICAL APPLICATION EXAMPLE
22uH
AA1700
Constant Current White LED driver
Vout
D1
1N5821
QA
QB
SP
Vcc
Vin
33uF
CTL
0.1uF
2
3
4
7
6
5
CLK
GND
P0
12KΩ
10uF
Q1
FZT489
0.1uF
390O (*adjustable)
270pF
3KΩ
Q2
C1815
R
LED
R
LED
CTL-IN
Note:
1.R
LED
=0.5V / I
LED
, I
LED
: LED Current, for LED brightness control
where 0.5V is the feedback reference voltage and
I
LED
= 20mA (R
LED
= 25Ω) for typical application
2.Output voltage Vout is given by Vout=n * Vf + 0.5V where
Vf : LED forward voltage drop
n : Number of LEDs in series connection
3. The sample described above is an inductive-boost driver, so it should
follow the following equation.
V
IN
< V
OUT
+ V
D1
, where V
D1
is forward voltage drop of diode D1.
4.To avoid some LEDs are damaged and conduce to high
current of damaged LED series, the constant current control
should be Included by QA, QB, etc. .
5. The chock Inductor (L1) Is for noise filter.
©Copyright
Agamem Microelectronics Inc.
7
www.agamem.com.tw
other LED series
2007/1/22
L1
56uH
IN
1
8
ER
AA1700
AGAMEM [ AGAMEM MICROELECTRONIC INC. ]
