AL5809

Document number: DS36625 Rev. 3 - 2

4 of 13

www.diodes.com

October 2014

© Diodes Incorporated

AL5809

Application Information

Description

The AL5809 is a constant current linear LED driver and can be placed in series with LEDs as a High Side or a Low Side constant current

regulator. The AL5809 offers various current settings from 15mA up to 150mA and different current settings available upon request (contact:

Diodes local sale office at http://www.diodes.com).

Simple LED String

The AL5809 can be placed in series with LEDs as a Low Side/High Side constant current regulator. The number of LEDs can vary from one to

as many as supported by the input supply voltage. The designer needs to calculate the maximum voltage between In and Out by taking the

maximum input voltage less the voltage across the LED string (Figures 1 and 2).

VIN

Low Side LED String

IN

OUT

1

2

AL5809

VIN

High Side LED String

IN

OUT

1

2

AL5809

Figure 1 Low Side LED String Tapping

Figure 2 High Side LED String Tapping

The AL5809 can also be used on the high side of the LEDs, see Figure 2. The minimum system input voltage can be calculated by:

The LED current can be increased by connecting two or more AL5809 in parallel shown in Figure 3.

VIN

IN

OUT

IN

OUT

. . .

AL5809

AL5809

AL5809

AL5809

VIN

IN

OUT

IN

OUT

. . .

(a)Low Side Configuration

(b) High Side Configuration

Figure 3 Higher LED current by parallel configuration of AL5809