Diodes AL8843EV1 User manual

AL8843EV1 User Guide
AL8843EV1 Page 1 of 10
Dec 2017
www.diodes.com
General Description
The AL8843 is a hysteresis mode DC-DC
step-down converter, designed for driving
single or multiple series connected LEDs
efficiently from a voltage source higher
than the LED voltage. The device can
operate from an input supply between 4.5V
and 40V and provide an externally
adjustable output current up to 3A.
Depending upon supply voltage and
external components, this converter can
provide up to 60W of output power.
The AL8843 integrates the power switch
and a high-side output current sensing
circuit, which uses an external resistor to
set the nominal average output current.
Dimming can be realized by applying an
external control signal to the CTRL Pin. The
CTRL Pin will accept either a DC voltage
signal or a PWM signal.
The soft-start time can be adjusted by an
external capacitor from the CTRL Pin to
Ground. Applying a voltage of 0.3V or lower
to the CTRL Pin will shut down the power
switch.
Applications
LED Retrofit for Low Voltage Halogen
Low Voltage Industrial Lighting
LED Backlighting
Illuminated Signs
External Driver with Multiple Channels
Key Features
Wide Input Voltage Range: 4.5V to 40V
Output Current up to 3A
Internal 40V NDMOS Switch
Typical 4% Output Current Accuracy
Single Pin for On/Off and Brightness
Control by DC Voltage or PWM Signal
Recommended Analog Dimming Range:
10% to 100%
Soft-Start
High Efficiency (Up to 97%)
LED Short Protection
Inherent Open-Circuit LED Protection
Over Temperature Protection (OTP)
Up to 1MHz Switching Frequency
SO-8EP Packages Available in Green
Molding Compound (No Br, Sb)
AL8843EV1 Specifications
Parameter
Value
Input Voltage
5VDC to 40VDC
LED Current
2A
Number of LEDs
1~10 LEDs
XYZ Dimension
63mm x 40mm x 10mm

AL8843EV1 User Guide
AL8843EV1 Page 2 of 10
Dec 2017
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Figure 1: Top View
Figure 2: Bottom View
Connection Instructions
Power Supply Input: 5~40VDC (VIN, GND)
CTRL: Internal voltage ref. pin (2.5V). This pin can be used to achieve dimming and for switching
the output current off. Leave floating for normal operation.
PWM Signal Input: Remove C4, apply PWM signal to CTRL (CTRL, GND)
Analog Signal Input: Connect 470nF capacitor to C4, apply analog signal to CTRL (CTRL, GND)
LED A: LED A connects to the external LED anode
LED K: LED K connects to the external LED cathode

AL8843EV1 User Guide
AL8843EV1 Page 3 of 10
Dec 2017
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Evaluation Board Schematic
Figure 3: Evaluation Board Schematic

AL8843EV1 User Guide
AL8843EV1 Page 4 of 10
Dec 2017
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Evaluation Board Layout
Figure 4: PCB Board Layout Top View
Figure 5: PCB Board Layout Bottom View
Quick Start Guide
1. By default, the evaluation board is preset at 2A LED Current by R1 and R2.
2. Non-dimming operation: Leave CTRL pin floating for normal operation.
3. Power Supply: Connect the 5~40VDC to VIN & GND pin to supply the system and AL8843.
4. PWM Dimming: Remove C4; apply a PWM signal (low level < 0.3V and high level > 2.5) to
CTRL pin to dim the LEDs. The recommended PWM signal frequency is from 100Hz to 1kHz,
and the PWM duty is from 1% to 100%.
5. Analog Dimming: Connect 470nF capacitor to C4; the CTRL pin may be driven between 0.4V
and 2.5V adjusting the output current from 10% to 100% of ILED.

AL8843EV1 User Guide
AL8843EV1 Page 5 of 10
Dec 2017
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Bill of Material
Ref
Value
Package
Part Number
Manufacturer
Notes
U1
AL8843
SO-8EP
AL8843SP-13
Diodes
DC-DC converter
D1
60V, 3A
SMB
B360B-13-F
Diodes
Schottky diode
R1, R2
0R100
1206
Generic
+/-1%
R3
0R
0805
Generic
+/-5%
C1, C2
4.7uF, 50V
1210
C1210X475K5RAC
Generic KEMET
X7R
C3
100nF,100V
0805
Generic
NMC0805X7R104K100
NIC
Components
X7R
C4
Not Fitted
0805
Optional soft start
capacitor
C5, C6
1uF, 100V
1206
Generic
NMC1206X7R105K100
NIC
Components
X7R
L1
82uH
1280
744770182
Würth Elektronik
82uH, ~0.16R, ~2.45A
Note: The component part numbers are correct at the time of publication. Diodes Inc reserves the right to
substitute other parts where necessary, without further notification.

AL8843EV1 User Guide
AL8843EV1 Page 6 of 10
Dec 2017
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Functional Waveforms
Switching waveform(Vin=20V, 3LEDs)
(Y-Vin, R-SW, B-CTRL, G-IL)
Start-up waveform(Vin=20V, 3LEDs)
(Y-Vin, R-SW, B-CTRL, G-IL)
Soft Start waveform
(Vin=20V, 3LEDs, C4=10nF)
(Y-Vin, R-SW, B-CTRL, G-IL)
PWM Dimming waveform(Vin=20V, 3LEDs)
(PWM frequency=500Hz, Duty=80%)
(Y-Vin, R-SW, B-CTRL, G-IL)

AL8843EV1 User Guide
AL8843EV1 Page 7 of 10
Dec 2017
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Functional Waveforms
PWM Dimming waveform(Vin=20V, 3LEDs)
(PWM frequency=500Hz, Duty=50%)
(Y-Vin, R-SW, B-CTRL, G-IL)
PWM Dimming waveform(Vin=20V, 3LEDs)
(PWM frequency=500Hz, Duty=20%)
(Y-Vin, R-SW, B-CTRL, G-IL)
LED open protection(Vin=20V, 3LEDs)
(Y-Vin, R-SW, B-CTRL, G-IL)
LED short protection(Vin=20V, 3LEDs)
(Y-Vin, R-SW, B-LED K, G-IL)

AL8843EV1 User Guide
AL8843EV1 Page 8 of 10
Dec 2017
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0 5 10 15 20 25 30 35 40
70
72
74
76
78
80
82
84
86
88
90
92
94
96
98
100
Efficiency(%)
Vin(V)
Vo=3.3V
Vo=6.6V
Vo=9.9V
Vo=13.2V
Vo=16.5V
Vo=19.8V
Vo=23.1V
Vo=26.4V
Vo=29.7V
Vo=33V
510 15 20 25 30 35 40
0
50
100
150
200
250
300
Frequency(kHz)
Vin(V)
Vo=3.3V
Vo=6.6V
Vo=9.9V
Vo=13.2V
Vo=16.5V
Vo=19.8V
Vo=23.1V
Vo=26.4V
Vo=29.7V
Vo=33V
0 5 10 15 20 25 30 35 40
1500
1600
1700
1800
1900
2000
2100
2200
ILED(mA)
Vin(V)
Vo=3.3V
Vo=6.6V
Vo=9.9V
Vo=13.2V
Vo=16.5V
Vo=19.8V
Vo=23.1V
Vo=26.4V
Vo=29.7V
Vo=33V
Functional Data Curves
Efficiency vs. Input Voltage
LED Current vs. Input Voltage
Operating Frequency vs. Input Voltage
PWM Dimming(Vin=20V, 3LEDs)
Analog Dimming(Vin=20V, 3LEDs)
010 20 30 40 50 60 70 80 90 100
0
200
400
600
800
1000
1200
1400
1600
1800
2000
ILED(mA)
PWM Duty(%)
fPWM=100Hz
fPWM=500Hz
fPWM=1kHz
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
ILED(mA)
VCTRL pin voltage(V)

AL8843EV1 User Guide
AL8843EV1 Page 9 of 10
Dec 2017
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Thermal Test
Figure 6: Top (Vin=20V, 3LEDs, Burn-in time=60min)
Figure 7: Bottom (Vin=20V, 3LEDs, Burn-in time=60min)

AL8843EV1 User Guide
AL8843EV1 Page 10 of 10
Dec 2017
www.diodes.com
IMPORTANT NOTICE
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DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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