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AL8807EV3

P1-P3P4-P6P7-P8
Issue 1 – December 2011 www.diodes.com
© Diodes Incorporated, 2011
AL8807EV3 EVALUATION BOARD USER GUIDE
DESCRIPTION
The AL8807EV3, Figure 1, is a double sided evaluation board for the AL8807 step-down, or ‘buck’,
LED driver with internal switch. The evaluation board is preset to drive 1A into a single LED, or
multiple LEDs, the maximum number of which depends on their total forward voltage drop and the
supply voltage.
The operating voltage is nominally 36 volts, but it can be reduced to a minimum of 6 volts. The 68uH
inductor used in the circuit is based on this nominal supply. The evaluation board should be
connected as in Figure 1 below.
Note: The evaluation board does not have reverse supply protection.
The nominal current, 1A, is set with the 0R1 sense resistor, R1.
Terminal CTRL provides a connection point for DC or PWM dimming and shutdown.
Warning: At 36V nominal operation with 1A output, the LED will be hot and very bright
Figure 1: AL8807EV3 evaluation board and connection diagram
1-8
LEDs
6-36VDC
V
+
AL8807EV3
Issue 1 – December 2011 www.diodes.com
© Diodes Incorporated 2011
2
AL
8807
EV3
int Definition
Name
Description
Vin Positive supply voltage. 6 to 36V
GND
Supply Ground (0V).
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.
LED A LED A connects to the external LED anode
LED K LED K connects to the external LED cathode
AL
8807
DEVICE DESCRIPTION
The AL8807 is a continuous mode inductive driver in a SOT25 package, for driving one or more
series-connected LEDs efficiently from a voltage source higher than the LED voltage. The device
includes the output switch and a current sense circuit, which requires an external sense resistor to set
the nominal current up to 1A.
AL
8807
DEVICE FEATURES
• Drives one or more series-connected LEDs
• LEDs up to 1A.
• Internal 40V switch.
• Wide input voltage: 6V to 36V.
• Inherent open circuit LED protection.
• Brightness control using DC or PWM.
DEVICE APPLICATIONS
• LED flashlights.
• High Power LED driving.
• Low-voltage halogen replacement LEDs.
• Automotive lighting.
• Illuminated signs.
AL
8807
Device Packages, Pin and Definitions
1
2
3
4 5
6
7
8
GND
CTRL
GND
N.C.
SET
V
IN
SW
SW
Top View
SOT25 package MSOP8EP package
AL
8807
Device Pin Definition
Name
Pin No
Description
SW 1 Drain of NDMOS switch.
GND 2 Ground (0V).
CTRL 3 Internal voltage ref. pin (2.5V) :
• Leave floating for normal operation.
• Connect to GND to turn off output current.
• Drive with DC voltage (0.4V to 2.5V) or with PWM (up to 5V
logic level) signal to adjust output current
SET 4 Connect a sense resistor, R1,
from the SET pin to VIN to sense the
nominal output current. Nominal I
out
= 0.1/ R1
VIN 5 Input voltage: 6V to 36V. Decouple to ground with a 2.2uF or higher
ceramic capacitor.
AL8807EV3
Issue 1 – December 2011 www.diodes.com
© Diodes Incorporated 2011
3
ORDERING INFORMATION
EVALBOARD ORDER
NUMBER
AL8807EV3
Please note: Evaluation boards are subject to
availability and qualified sales leads.
DEVICE ORDER NUMBER
AL8807MP-13
AL8807EV3 EVALUATION BOARD REFERENCE DESIGN
The AL8807EV3 is configured to the reference design in Figure 2.
The operating voltage is up to 36V. The nominal current is set at 1A with a 0R1 sense resistor R1.
The circuit operates in continuous mode between approximately 40kHz and 130kHz, depending on
the input voltage, and with a 68uH inductor and one LED.
Both DC and PWM dimming can be achieved by driving the CTRL 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 I
LED
.
Driving the CTRL pin below 0.4V will shut down the output current.
A PWM signal (low level ≤ 0.4V and high level > 2.5) allows the output current to be adjusted above or
below the level set by the resistor connected to SET input pin. The PWM frequency can be around
100Hz to 1kHz, providing a resolution of 10 bits.
For low frequency PWM, C2 should be removed from the evaluation board, to give a more accurate
duty cycle .
Shorting R2 will connect the test pin CTRL to device pin CTRL, if required.
For other reference designs or further applications information, please refer to the AL8807 datasheet.
Figure 2: Schematic diagram
P1-P3P4-P6P7-P8

AL8807EV3

Mfr. #:
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Description:
EVAL BRD LED DRIVER W/SWITCH
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