AL1676

Document number: DS38290 Rev. 1 - 2

9 of 15

www.diodes.com

February 2016

© Diodes Incorporated

AL1676

The detection circuit is activated after the LEB time. When the detection circuit sense the CS voltage is higher than 1V, the IC will turn off the

switch to limit the output current. It automatically provides protection for the maximum LED current during operation. A propagation delay exists

between over current detection and actual source-switch off, so the actual peak current is a little higher than the OCP level set by the R5.

Over-Voltage Protection and Output-Open Protection (OVP)

The AL1676 has output open voltage protection when the LED is open, which can prevent the output voltage from increasing to a very high value.

This feature can help the system designer to select a smaller volume capacitor. The output voltage is set by the external resistor R3 shown in

Figure 1.

_

1

R5

CS

OFF OVP

OVP

LV

t

V







Where,

The output voltage is set by R3, and R3 is calculated as:

5

20

1

20

3

_

_

_

R

V

C

L

V

V

C

t

V

R

OVP

REF

REF

ROVP

CS

REF

OVP

OFF

REF

ROVP



















Output-Short Protection (OSP)

Thermal Foldback Protection (TFP)

The AL1676 has a thermal foldback function and adopts self-adaptive control method, which can prevent the system from breaking down caused

by high temperature. The overheating temperature is set at +150°C typical, when the junction temperature of the IC is higher than +150°C typical,

the device will linearly decrease the internal reference voltage to decrease the output current. As a result of this feature, the device can control the

system

’s output power at high ambient temperature, to control the quantity of heat of the system. This enhances the safety of the system at high

temperature.

The thermal foldback waveform is shown below:

Figure 2. Thermal Foldback Waveform