Diodes AL5802EV1 User manual

Issue 1 – October 2011 www.diodes.com
© Diodes Incorporated, 2011
AL5802EV1 USER GUIDE
Description
The board is intended for the evaluation of
AL5802, an adjustable current sink linear
LED driver in the SOT26 package. The
device is ideal for driving 20mA to 120mA
LED.
When an input voltage higher than the
forward voltage of the LED string is applied
to the board, the board supplies a fixed
current to the LED string connected to its
output. The board can operate from 5V to
24V DC power supplies. The maximum input
voltage is up to 30V.
The board has been designed for driving low
current LEDs with typical current of 20mA,
50mA or 100mA. Jumpers 1, 2 and 3 on the
evaluation board set the value of the LED
current.
The board also provides an ENABLE input
which can be used for PWM dimming of the
LED string. The LED current will shut down
when the ENABLE input is pulled down to
ground either with an external open-collector
NPN transistor, or open-drain N-channel
MOSFET.
Ordering Information
ORDER NUMBER
AL5802EV1
Please note evaluation boards are subject to availability and qualified leads
Figure 1. AL5802 evaluation board
DMM
PSU
20V
200mA

AL5802EV1
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Quick Start Guide
Required Test Equipment
20V 1A adjustable power supply, Digital Multi-Meter (DMM) and low current LEDs
Constant Current LED Driving Operation
1. Set the power supply to 20V for a string of 5 LEDs.
2. Set the current limit to 200mA.
3. Connect up the AL5802EV1 to the equipment as in Figure 1 above.
4. Set DMM to measure the LED current.
5. Set jumper to JP1 position. Only one jumper should be fitted at any time.
6. Switch on the power supply and check that the LED lights up.
7. Check that the current measured on DMM is 100mA +/- 10mA.
8. Switch off the power supply and set jumper to JP2 position.
9. Switch on the power supply and check that the LED lights up.
10. Check that the current measured on DMM is 50mA +/- 5mA.
11. Switch off the power supply and set jumper to JP3 position.
12. Switch on the power supply and check that the LED lights up.
13. Check that the current measured on DMM is 20mA +/- 2mA.
AL5802EV1 Schematic
1nF C1
GND
Vin
ENABLE
LEDA
LEDK
3R
R1 11R5
R2 28R
R3
1
2
JP1
1
2
JP2
1
2
JP3
VCC
GND
CATHODE
Anode
1
OUTOUT
2
BIASBIAS
4
GNDGND
3
ENEN
5
REXTREXT
6
REXTREXT
U1
AL5802
Figure 2. Evaluation board schematic diagram

AL5802EV1
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© Diodes Incorporated
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Parts List
Designator Description Package Part Number Manufacturer
U1 Linear mode constant sink LED driver SOT23-6 AL5802 Diodes Inc.
R1 Resistor, 6K49 +/- 1% 250ppm 250mW 1206 - Generic
R2 Resistor, 13R +/- 1% 250ppm 125mW 0805 - Generic
R3 Resistor, 33R +/- 1% 250ppm 125mW 0805 - Generic
Table 1. Parts list
Performance
Figure 3 shows the performance of the AL5802 when used to regulate LED current. With
jumper 1 fitted, a load of 5 series connected low current LEDs and a supply voltage of
20VDC, the LED current is measured around 100mA at 25°C PCB temperature. Over the
typical lighting board temperature range, the LED current changes from 106mA at 0°C PCB
temperature to 85mA at 85°C.
Figure 3. LED current vs. PCB board temperature
PWM dimming can be achieved by driving the on-board ENABLE input. An external open-
collector NPN transistor or open-drain N-channel MOSFET can be used to drive the EN pin.
The PWM frequency can be around 100Hz to 1KHz. Figures 4 to 6 show the LED current
variation as the duty cycle of a 400Hz PWM dimming signal changes.

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Figure 4. Duty Cycle vs. output Current for JP1 Configuration (100mA) at 400Hz
Figure 5. Duty Cycle vs. Output Current for JP2 Configuration (50mA) at 400Hz

AL5802EV1
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Figure 6. Duty Cycle vs. Output Current for JP3 Configuration (20mA) at 400Hz
PCB Copper Layout & Silk Screen –Top
Figure 7. PCB layout
The bottom layer is a solid plane connected to LED K

AL5802EV1
Issue 1 – October 2011 www.diodes.com
© Diodes Incorporated
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INTENTIONALLY BLANK

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Issue 1 – October 2011 www.diodes.com
© Diodes Incorporated
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INTENTIONALLY BLANK

AL5802EV1
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© Diodes Incorporated
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