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AL88070B

Document number: DS36191 Rev. 1 - 2

1 of 18

www.diodes.com

March 2014

NEW PRODUCT

L8807B

HIGH EFFICIENCY 36V 1.3A PWM DIMMABLE BUCK LED DRIVER

Description

The AL8807B is a step-down DC/DC converter designed to drive

LEDs with a constant current. The device can drive up to 9 LEDs,

depending on the forward voltage of the LEDs, in series from a

voltage source of 6V to 36V. Series connection of the LEDs provides

identical LED currents resulting in uniform brightness and eliminating

the need for ballast resistors. The AL8807B switches at frequency up

to 1MHz with controlled rise and fall times to reduce EMI. This

allows the use of small size external components, hence minimizing

the PCB area needed.

Maximum output current of AL8807B is set via an external resistor

connected between the V

and SET input pins. Dimming is

achieved by applying a PWM signal at the CTRL input pin. An input

voltage of 0.4V or lower at CTRL switches off the output MOSFET

simplifying PWM dimming.

Features

 LED driving current up to 1.3A

 Better than 5% accuracy

 High efficiency up to 96%

 Optimally controlled switching speeds

 Operating input voltage from 6V to 36V

 PWM input for dimming control

 Open-Circuit LED protection

 LED Chain Short Circuited

 Over-Temperature Protection

 MSOP-8EP Available in “Green” Molding Compound (No Br,

Sb) with lead Free Finish/ RoHS Compliant

 Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)

 Halogen and Antimony Free. “Green” Device (Note 3)

Pin Assignments

Applications

 MR16 lamps

 General illumination lamps

 12V powered LED Lamps

 24V powered LED Lamps

Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.

2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free,

"Green" and Lead-free.

3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl)

and <1000ppm antimony compounds.

Typical Application Circuit

(Top View)

MSOP-8E

SET

GND

CTRL

N/C

AL8807B

SETSW

CTRL

GND

PWM Dimming

Input:

6 ~ 36V

Summary of content (18 pages)

PAGE 1
AL8807B HIGH EFFICIENCY 36V 1.3A PWM DIMMABLE BUCK LED DRIVER Description Pin Assignments The AL8807B is a step-down DC/DC converter designed to drive LEDs with a constant current. The device can drive up to 9 LEDs, depending on the forward voltage of the LEDs, in series from a (Top View) voltage source of 6V to 36V. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors.
PAGE 2
AL8807B Pin Descriptions SET GND Pin Number 1 2, 3 CTRL 4 SW N/C 5, 6 7 VIN 8 EP EP NEW PRODUCT Pin Name Function Set Nominal Output Current Pin. Configure the output current of the device. GND Pins Dimming and On/Off Control Input.  Leave floating for normal operation. (VCTRL = VREF = 2.5V giving nominal average output current IOUTnom = 0.1/RS)  Drive to voltage below 0.4V to turn off output current  A PWM signal ( 2.
PAGE 3
AL8807B Absolute Maximum Ratings Symbol ESD HBM ESD MM Ratings 2.5 200 Unit kV V VIN Continuous VIN Pin Voltage Relative to GND -0.3 to +40 V VSW SW Voltage Relative to GND -0.3 to +40 V CTRL Pin Input Voltage -0.3 to +6 V 1.6 A VCTRL ISW-RMS ISW-PK NEW PRODUCT Parameter Human Body Model ESD Protection Machine Model ESD Protection DC or RMS Switch Current MSOP-8EP Peak Switch Current (<10%) Junction Temperature TJ 2.
PAGE 4
AL8807B Typical Performance Characteristics (@TA = +25°C, unless otherwise specified.) 400 80 350 60 300 40 ICTRL (µA) IIN (µA) 250 200 20 0 150 -20 100 VCTRL = 0V VSET = VIN TA = 25°C 50 0 0 -40 -60 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.0 VCTRL (V) 9 12 15 18 21 24 27 30 33 36 VIN (V) Figure 1. Supply Current (not switching) vs. Input Voltage 3 6 Figure 2 ICTRL vs. VCTRL 3 2.52 VCTRL = Open VSET = VIN = 12V 2.5 2.51 VCTRL (V) VCTRL (V) 2 1.5 2.50 1 0 2.
PAGE 5
AL8807B NEW PRODUCT Typical Performance Characteristics (cont.) (@TA = +25°C, unless otherwise specified.) Figure 8. Duty Cycle vs. Input Voltage Figure 7 ILED vs. PWM Duty Cycle Figure 9. Efficiency vs. Input Voltage Figure 10. On-time vs. Input Voltage Figure. 11 SW Output Rise Time AL88070B Document number: DS36191 Rev. 1 - 2 Figure. 12 SW Output Fall Time 5 of 18 www.diodes.
PAGE 6
AL8807B NEW PRODUCT Typical Performance Characteristics (670mA LED current) (@TA = +25°C, unless otherwise specified.) Figure 13. LED Current Deviation vs. Input Voltage Figure 15. LED Current Deviation vs. Input Voltage Figure 17. LED Current Deviation vs. Input Voltage AL88070B Document number: DS36191 Rev. 1 - 2 6 of 18 www.diodes.com Figure 14. Switching Frequency vs. Input Voltage Figure 16. Switching Frequency vs. Input Voltage Figure 18. Switching Frequency vs.
PAGE 7
AL8807B NEW PRODUCT Typical Performance Characteristics (1A LED currentMSOP-8EP) (@TA = +25°C, unless otherwise specified.) Figure 19. LED Current Deviation vs. Input Voltage Figure 20. Switching Frequency vs. Input Voltage Figure 21. LED Current Deviation vs. Input Voltage Figure 22. Switching Frequency vs. Input Voltage Figure 23. LED Current Deviation vs. Input Voltage Figure 24. Switching Frequency vs. Input Voltage AL88070B Document number: DS36191 Rev. 1 - 2 7 of 18 www.diodes.
PAGE 8
AL8807B NEW PRODUCT Typical Performance Characteristics (1.3A LED current MSOP-8EP) (@TA = +25°C, unless otherwise specified.) Figure 25. LED Current Deviation vs. Input Voltage Figure 26. Switching Frequency vs. Input Voltage Figure 27. LED Current Deviation vs. Input Voltage Figure 28. Switching Frequency vs. Input Voltage Figure 29. LED Current Deviation vs. Input Voltage Figure 30. Switching Frequency vs. Input Voltage AL88070B Document number: DS36191 Rev. 1 - 2 8 of 18 www.diodes.
PAGE 9
AL8807B Application Information The AL8807B is a hysteretic (also known as equal ripple) LED driver with integrated power switch. It is available in two packages that provide a PCB area-power dissipation capability compromise. It is recommended that at higher LED currents/smaller PCBs that the MSOP-8EP version is used to maximize the allowable LED current over a wider ambient temperature range. AL8807B Operation In normal operation, when voltage is applied at +VIN, the AL8807B internal switch is turned on.
PAGE 10
AL8807B Applications Information (cont.) PWM Dimming LED current can be adjusted digitally, by applying a low frequency Pulse Width Modulated (PWM) logic signal to the CTRL pin to turn the device on and off. NEW PRODUCT This will produce an average output current proportional to the duty cycle of the control signal. In particular, a PWM signal with a max resolution of 10bit can be applied to the CTRL pin to change the output current to a value below the nominal average value set by resistor RSET.
PAGE 11
AL8807B Applications Information (cont.) Figures 35 and 36 show the PWM dimming performance of the AL8807B with a range of PWM frequencies with a nominal switching frequency of NEW PRODUCT 530kHz.
PAGE 12
AL8807B Applications Information (cont.) Reducing Output Ripple Peak to peak ripple current in the LED(s) can be reduced, if required, by shunting a capacitor C2 across the LED(s) as shown already in the circuit schematic. A value of 1μF will reduce the supply ripple current by a factor three (approx.). Proportionally lower ripple can be achieved with higher capacitor values.
PAGE 13
AL8807B Applications Information (cont.) Inductor Selection (cont.) The chosen coil should have a saturation current higher than the peak output current and a continuous current rating above the required mean NEW PRODUCT output current. Suitable coils for use with the AL8807B are listed in the table below: L DCR ISAT Manufacturer Part No. (µH) (V) (A) MSS1038-333 33 0.093 2.3 CoilCraft www.coilcraft.com MSS1038-683 68 0.213 1.5 NPIS64D330MTRF 33 0.124 1.1 NIC www.niccomp.
PAGE 14
AL8807B Applications Information (cont.) Figure 39, shows the power derating of the AL8807BMP on an FR4 51x51mm PCB with 2oz copper standing in still air. Changing the PCB dimensions, material, amount of metal associated with the thermal and other PCB components will change the AL8807BMP’s junction-ambient thermal impedance.
PAGE 15
AL8807B Applications Information (cont.) EMI and Layout Considerations The AL8807B is a switching regulator with fast edges and measures small differential voltages; as a result of this care has to be taken with decoupling and layout of the PCB.To help with these effects the AL8807B has been developed to minimise radiated emissions by controlling the switching speeds of the internal power MOSFET.
PAGE 16
AL8807B Applications Information (cont.) Fault Condition Operation Open Circuit LEDs The AL8807B has by default open LED protection. If the LEDs should become open circuit the AL8807B will stop oscillating; the SET pin will rise to VIN and the SW pin will then fall to GND. No excessive voltages will be seen by the AL8807B.
PAGE 17
AL8807B Part Number Package Code Packaging AL8807BMP-13 MP MSOP-8EP Quantity 2500 Packing: 13” Tape and Reel Tape Width Part Number Suffix 12mm -13 Marking Information (1) MSOP-8EP (Top View) 8 7 Logo 6 5 YW XE Part Number AL8807B 1 2 3 A~Z : Green MSOP-8EP Y : Year : 0~9 W : Week: A~Z : 1~26 week; a~z : 27~52 week; z represents 52 and 53 week 4 Part Number Package AL8807BMP-13 MSOP-8EP Package Outline Dimensions (All dimensions in mm.) Please see AP02002 at http://www.diodes.
PAGE 18
AL8807B Suggested Pad Layout Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version. 1) MSOP-8EP X C Y NEW PRODUCT G Y2 Dimensions C G X X1 Y Y1 Y2 Y1 X1 Value (in mm) 0.650 0.450 0.450 2.000 1.350 1.700 5.