AL88070B

Document number: DS36191 Rev. 1 - 2

9 of 18

www.diodes.com

March 2014

© Diodes Incorporated

AL8807B

Application Information

The AL8807B is a hysteretic (also known as equal ripple) LED driver with integrated power switch. It is available in two packages that provide a

PCB area-power dissipation capability compromise. It is recommended that at higher LED currents/smaller PCBs that the MSOP-8EP version is

used to maximize the allowable LED current over a wider ambient temperature range.

AL8807B Operation

inductor L1, and the LEDs. The current ramps up linearly, and the ramp rate is determined by the input voltage +Vin and the inductor L1.

proportional voltage to the input of the internal comparator.

the LEDs and the Schottky diode D1, and back to the supply rail, but it decays, with the rate of decay determined by the forward voltage drop of

the LEDs and the Schottky diode.

applied at the input of the internal comparator. When this voltage falls to the internally set lower threshold, the internal switch is turned on again.

LED Current Control

The LED current is controlled by the resistor R1 in Figure 31.

Figure 31 Typical Application Circuit

Figure 32 Typical Operating Waveform (C2 not fitted)

1

R

V

I

THD









m

150

66

.

0

1

.

0

I

V

1

R

LED

THD

AL8807B

C2

R1

C1

D1

L1

PWM Dimming

Input:

6 ~ 36V

2 LEDs

20ns/div

No C2

Ch2: 2V/div

Ch4: 100mA/div

Ch4: LED Current

Ch2: SW Pin