AL5815/AL5816

Document number: DS39991 Rev. 3 - 2

8 of 12

www.diodes.com

July 2018

© Diodes Incorporated

AL5815/AL5816

Multiple LED Strings in Parallel

AL5815 and AL5816 can drive more than one channel of LED strings. As shown in Figure 2, the sense voltage of two channels’ (or more) output

current can be implemented by connecting the voltage of one sense resistor to the FB pin.

By utilizing the same type transistors, sense resistors and series base resistor, the current will match.

Q1

Q2

LED1

LED2

Vin

OUT

FB

Figure 2. Two LED Strings in Parallel

The output current can be set as following:

and Rs1 and Rs2 should be matched.

ENB/PWM Dimming

The ENB pin can be used for PWM dimming by enabling and disabling the device to turn-on and turn-

off the AL5815’s external transistor. A voltage

higher than 2.0V will turn off OUT signal while a signal lower than 0.4V turns on the external transistor.

Due to the soft-

start delay of the AL5815’s ENB function, only low frequency (200Hz or lower) dimming is supported in this device. The AL5816

does not have a soft start thus its PWM pin can be driven with PWM frequency higher than 200Hz.

Figure 3. PWM Dimming Curve of AL5815

0

10

20

30

40

50

60

70

80

90

100

0

5

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Duty Cycle [%]

LED Current (%) vs. Duty Cycle by Switching Frequency

200Hz

ideal