AL5817

Document number: DS40391 Rev. 3 - 2

2 of 13

www.diodes.com

August 2018

© Diodes Incorporated

AL5817

Typical Application Circuit

AL5817

VCC

REF

FB

VFAULT

OUT

VSET

GND

ENB

C1

R2

R3

D1

R4

R5

R1

Q1

AL5817

VCC

REF

FB

VFAULT

OUT

VSET

GND

ENB

C1

R2

R3

D1

R4

R5

R1

Q1

Figure 1

Pin Descriptions

Pin Number

Pin Name

Function

1

VCC

Supply input

2

REF

Internal reference voltage.

The maximum recommended output current is 50µA and the maximum recommended capacitor

connected from this pin to GND is less than 100pF.

A potential divider from REF to VSET can be used to accurately set the output LED current.

3

VSET

LED current setting threshold.

The voltage on VSET sets the reference voltage for the FB pin. This pin is pulled down internally if left

floating. The capacitance if needed between VSET and GND is recommended to be less than 1nF.

4

GND

Ground

5

FB

Feedback input.

When control loop is operating in linear mode the FB pin will be regulated to the level set by VSET. This

pin is pulled up internally if left floating.

A capacitor may be added between FB and GND to improve noise rejection. Value needs to be limited

100pF or less.

6

OUT

Driving output

7

ENB

Chip Enable

An input voltage >2V disables the device and external transistor drive.

This pin can be used for low frequency PWM dimming of the LED current.

8

VFAULT

Input for LED-open detection.

When LED-open detection function is active, if VFAULT is brought lower than approximately 2.5V the

device output will be turned off and will auto-retry driving the output to see if the fault still exists.

A PWM dimming function will be realized by adding an open collector/drain signal on this pin.

EP

EP

Exposed Pad (bottom).

Recommended to be connected to a large-area contiguous copper GND plane for effective thermal

dissipation. Do not use as the IC

’s only electrical GND connection.