Agamem Microelectronics Inc.

AA1700

PRELIMINARY

Constant Current White LED driver

©Copyright Agamem Microelectronics Inc.

www.agamem.com.tw

2007/1/22

8

4

3

2

1

5

6

7

8

Q2

C1815

P0

GND

CLK

ER

IN

SP

Vcc

CTL

Note:

1.Light striking the surface of the Cds causes a decrease in resistance, while darkness

produces a higher resistance. When the light is bright, Q3 is on and Q2 is off, AA1700

will enter stand-by mode and there is no output current provided. When the light is dark,

Q3 is off and Q2 is on, AA1700 will output current and driver the IR LEDs. If the light Is

gray, the Q2 and Q3 will enter active mode, the impedance of Cds will decide the

collector current of Q3 and also Impact on the Internal impedance of Q2, so the driving

current can be controlled.

2.VR1 is for light sensitive control, the value will decide how darkness of the light source

the IR LEDs will brighten.

CdS Light

Sensitive Resistor

VR1

50K

Q3

C1815

R7

300Ω

Vcc

D3

R2

C8

10uF

390Ω

R8

4.7KΩ

CDS Control for IR LED