AL8806EV4 User Guide Issue 2

AL8806EV4 USER GUIDE
Performance
•
•
•
•
•
•
Introduction
This evaluation circuit demonstrates the
AL8806 High Efficiency 30V 1.5A Buck LED
Driver.
For detailed information on the
AL8806, please see the datasheet at:
9V to 30V DC input (with 2 LEDs)
1.5A LED current
Drives 1 LED or several LEDs in series
Brightness control using DC or PWM
Inherent open circuit LED protection
Ambient temperature range
-40°C to +105°C
http://www.diodes.com/datasheets/AL8806.pdf
The evaluation board is preset to drive its
maximum current of 1.5A into a single LED or
multiple LEDs, the maximum number of which
depends on their total forward voltage drop.
EMC filtering is included to meet international
standards including the radiated emission
requirements of EN55015 and EN55022
Class B.
Ordering Information
Order Number
AL8806EV4
The circuit operates in continuous switching
mode at a frequency of approximately 170kHz
when driving 2 LEDs each having a forward
voltage drop of approximately 3.4V at 1.5A.
Please note: Evaluation boards are subject
to availability and qualified sales leads.
The construction uses a double-sided FR4
printed circuit board, 63 x 40 x 1.7 mm with
2oz/sq ft copper (70µm). Components are
mounted on one side only.
Note: The evaluation board does not have
reverse supply protection.
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
1 of 12
AL8806EV4
Quick Start Guide
Suitable Test Equipment
Count
Description
1
Adjustable Power Supply, up to
30V 2A
2
Digital Multimeter
1
Digital Storage Oscilloscope
2
LED, high brightness, 2A,
connected on suitable heat
conducting PCB
Manufacturer
Part Number
Thurlby Thandar
CPX400A
Fluke
179
Tektronix
TDS2024B
CAUTION: The LEDs are very bright. Ensure they are
hidden from direct view, or covered with a dispersing
filter. The lid from an aerosol can is convenient for this.
Also the LEDs are very hot. Do not touch!!
Lamp Operation
1. Set the power supply to 12.0V but do not switch on. Set the current limit to 2.0A.
2. Connect up the AL8806EV4 board to the equipment as in Figure 1 below. Set DMM1 and
DMM2 to measure current up to 2A.
Figure 1: Test Schematic
3. Cover the LEDs to avoid dazzling.
4. Switch on the power supply. This should illuminate the LEDs. Note that the input current
(DMM1) depends on the LED volt drop. The input current is approximately 900mA if the total
LED volt drop is about 6.9V. The output current (DMM2) is approximately 1.47A. The input
voltage can be varied from approximately 8.5VDC to 30VDC and the current regulation
observed is typically within ±2%.
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
2 of 12
AL8806EV4
Observe Switching Waveform
5. The switching waveform can be observed on an oscilloscope.
6. Set the oscilloscope as follows:
Channel 1 sensitivity:
Time base:
Trigger Source:
Trigger Mode:
2V/div (at probe tip)
2µs/div
CH1
Auto
7. Connect the ground lead of a 10x probe to one of the plated fixing holes of the AL8806EV4,
and touch the probe tip onto the anode of D1 as in Figure 2 below. On the oscilloscope,
press RUN/STOP to capture the waveform. The cursor readout indicates a switching
frequency of 170kHz approximately –see Figure 3. (This frequency is dependent on the LED
volt drop.)
Figure 2: Waveform Capture
Dimming
Both DC and PWM dimming can be achieved by driving the CTRL input pin. For DC dimming, the
CTRL pin may be driven between 0.5V and 2.5V adjusting the output current from 25% to 100% of the
maximum value of 1.5A nominal. Driving the CTRL pin below 0.4V will shut down the output current.
A PWM signal (low level ≤ 0.4V and high level > 2.5V) allows the output current to be adjusted up to
1.5A. The PWM frequency can be around 100Hz to 1kHz, providing a resolution of 10 bits. In this
case, C3 should be removed or reduced from the evaluation board (see AL8806EV4 schematic
below) to give a more accurate control.
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
3 of 12
AL8806EV4
Figure 3: Oscilloscope Waveform
Radiated EMI Performance, EN55022:
Results of AL8806EV4 test at an independent EMC test facility.
Input: 12VDC
Load: 2 LEDS, 1.5A
(By courtesy of Cass Industries, Limited)
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
4 of 12
AL8806EV4
R2
Vin
Anode
ANODE
0R2
C8
NOT FITTED
C7
NOT FITTED
Vin
C6
NOT FITTED
C9
NOT FITTED
R1
0R1
C2
100nF
100V X7R
4
1
SET
SW
CTRL
NC
TAB
9
7
C3
100nF
100V X7R
SW
L1
Cathode
Cathode
33uH
1k
GND
5
SW
6
GND
CTRL pin
GND
R3
U1
AL8806
C11
1.5nF
100V C0G
C12
NOT FITTED
3
CTRL
C4
1uF
25V X7R
DFLS230LH
GND
CTRL
GND
D1
8
C1
C5
4.7uF
4.7uF
50V X7R 50V X7R
GND
GND
2
GND
Vin
GND
C10
1.5nF
100V C0G
GND
GND
GND
AL8806EV4 Schematic
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
5 of 12
AL8806EV4
PCB Copper Layout & Silk Screen – Top
PCB Copper Layout & Silk Screen –Bottom
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
6 of 12
AL8806EV4
Parts List
Count
Designator
Description
Package
2
C1 C5
Capacitor, 4.7µF 10%
50V X7R
Manufacturer
Part Number
1210
Kemet
C1210X475K5RAC
2
C2 C3
Capacitor, 100nF 10%
100V X7R
0805
NIC
Murata
NMC0805X7R104K100PF
GRM21BR71H104KA01L
1
C4
Capacitor, 1uF 10%
100V X7R
1206
generic
NIC
NMC1206X7R104K100
0
C6 – C9,
C12
NOT FITTED
2
C10 C11
Capacitor, 1.5nF 100V
COG
0805
generic
1
L1
Inductor, shielded,
33µH 20%
1
R1
Resistor, 0.1ohms 1%
1206
generic
1
R2
Resistor, 0.2ohms 1%
1206
generic
1
R3
Resistor, 1k 1%
0805
generic
1
D1
Diode, schottky, 30V
2A DFLS230LH
PowerDi123
Diodes Inc
DFLS230LH-7
1
U1
IC, LED Driver, AL8806
MSOP-8EP
Diodes Inc
AL8806MP8-13
Coilcraft
NIC
Würth
MSS1038-333ML
NPIS104F330MTRF
744-066-330
I/O
Count
Designator
Description
Function
Manufacturer
Part Number
1
VIN
Loop terminal
DC Supply + Input
Hughes
100-108
1
GND
Loop terminal
DC Supply – Input
Hughes
100-108
1
CTRL
Loop terminal
Dimming Control
Input
Hughes
100-108
1
LED A
Loop terminal
LED Anode Load
Hughes
100-108
1
LED K
Loop terminal
LED Cathode load
Hughes
100-108
Recommended Operating Conditions
Symbol
Parameter
Min
Max
Units
VDC
Input Supply Voltage, VDC
8
30
V
VOUT
Load voltage
0
VDC-1.5
V
TA
Operating Ambient
Temperature
-40
+105
°C
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
7 of 12
AL8806EV4
Current Setting
The LED current is set by the sense resistor value, RSENSE. On this PCB, there are two resistors in
parallel.
RSENSE = R1 * R2 / (R1 + R2)
For the schematic values this gives a resistance of 0.1 * 0.2 (0.1 + 0.2) = 0.0667 ohms.
The LED current flows through RSENSE. The sense voltage is 100mV, so the LED current is simply
ILED = 0.1/ RSENSE
For the schematic values this gives an LED current of 0.1/0.0667 = 1.500 A nominally. In practice
there is a slight reduction in current partly due to the resistance of the PCB copper, depending on the
PCB layout. At 1.5A this reduction is typically 1 to 2% using AL8806EV4.
The following table gives commercially available resistor values for typical current requirements,
allowing a current error of 3% maximum not including the effect of PCB copper. A power limit of
250mW is assumed for the 0805 size resistors with 50% de-rating.
LED Current
150mA
300mA
380mA
500mA
660mA
1A
1.1A
1.5A
R1, ohms
0.68
0.33
0.51
0.2
0.15
0.1
0.15
0.1
R2, ohms
DO NOT FIT
DO NOT FIT
DO NOT FIT
DO NOT FIT
DO NOT FIT
DO NOT FIT
0.22
0.2
Performance
The performance of the AL8806EV4 demonstrated shows the capability to regulate LED current. The
LED current of 1.5A is approximately 2% lower than the calculated value. This is partly due to copper
resistance. With a load of 2 LEDs, the current changes by less than ±2% over the input voltage range
from 9VDC to 30VDC. With 2 LEDs and a supply of 12VDC, the circuit operates in continuous mode
with a switching frequency of approximately 170kHz.
Power efficiency is approximately 95%.
The radiated emission of AL8806EV4 is approximately 18dB below the limits of EN55015 and is also
well within the limit of EN55022 Class B. (In the application of AL8806, the radiation depends very
much upon PCB layout and filtering.)
For further advice, please contact your local Diodes Field Applications Engineer, or one of our
sales offices listed on the back page of this document.
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
8 of 12
AL8806EV4
INTENTIONALLY BLANK
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
9 of 12
AL8806EV4
INTENTIONALLY BLANK
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
10 of 12
AL8806EV4
INTENTIONALLY BLANK
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
11 of 12
AL8806EV4
IMPORTANT NOTICE
DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS
DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).
Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements,
corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated
does not assume any liability arising out of the application or use of this document or any product described herein; neither
does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer
or user of this document or products described herein in such applications shall assume all risks of such use and will agree
to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated website,
harmless against all damages.
Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through
unauthorized sales channels. Should Customers purchase or use Diodes Incorporated products for any unintended or
unauthorized application, Customers shall indemnify and hold Diodes Incorporated and its representatives harmless
against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or
death associated with such unintended or unauthorized application.
Products described herein may be covered by one or more United States, international or foreign patents pending. Product
names and markings noted herein may also be covered by one or more United States, international or foreign trademarks.
LIFE SUPPORT
Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or
systems without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body, or
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use
provided in the labeling can be reasonably expected to result in significant injury to the user.
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably
be expected to cause the failure of the life support device or to affect its safety or effectiveness.
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support
devices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related
requirements concerning their products and any use of Diodes Incorporated products in such safety-critical, life support
devices or systems, notwithstanding any devices- or systems-related information or support that may be provided by
Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its representatives against any
damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.
Copyright © 2011, Diodes Incorporated
www.diodes.com
Sales offices
The Americas
Europe
Taiwan
Shanghai
Shenzhen
Korea
3050 E. Hillcrest Drive
Kustermannpark
7F, No. 50,
Rm. 606, No.1158
Room A1103-04,
6 Floor, Changhwa B/D,
Westlake Village,
CA 91362-3154
Tel: (+1) 805 446 4800
Fax: (+1) 805 446 4850
Balanstraße 59,
D-81541 München
Germany
Tel: (+49) 894 549 490
Fax: (+49) 894 549 4949
Min Chuan Road
Hsin-Tien
Taipei, Taiwan
Tel: (+886) 289 146 000
Fax: (+886) 289 146 639
Changning Road
Shanghai, China
Tel: (+86) 215 241 4882
Fax (+86) 215 241 4891
ANLIAN Plaza, #4018
Jintian Road
Futian CBD,
Shenzhen, China
Tel: (+86) 755 882 849 88
Fax: (+86) 755 882 849 99
1005-5 Yeongtong-dong,
Yeongtong-gu, Suwon-si,
Gyeonggi-do, Korea 443-813
Tel: (+82) 312 731 884
Fax: (+82) 312 731 885
Issue 2 – July 2011
www.diodes.com
© Diodes Incorporated 2011
12 of 12
Similar pages