AL8861 40V 1.5A BUCK LED DRIVER Description Pin Assignments The AL8861 is a hysteresis mode DC-DC step-down converter, designed for driving single or multiple series connected LEDs (Top View) efficiently from a voltage source higher than the LED voltage. The device can operate from an input supply between 4.5V and 40V and L 1 5 V X IN provide an externally adjustable output current up to 1A for TSOT25 package and 1.5A for SOT89-5 and MSOP-8EP packages. GND 2 Depending upon supply voltage and external components, this converter can provide up to 40W of output power. V 3 4 SET I SENSE The AL8861 integrates the power switch and a high-side output TSOT25 current sensing circuit, which uses an external resistor to set the nominal average output current. (Top View) Dimming can be realized by applying an external control signal to the VSET pin. The VSET pin will accept either a DC voltage signal or a L 1 5 V X IN PWM signal. The soft-start time can be adjusted by an external capacitor from the GND 2 VSET pin to Ground. Applying a voltage of 0.2V or lower to the VSET pin can turn off the output and make the device enter into standby state with low current consumption. V 3 4 I SET SENSE Features SOT89-5 Low BOM Counts Wide Input Voltage Range: 4.5V to 40V (Top View) Output Current up to 1.5A Internal 40V NDMOS Switch I 1 8 V SENSE IN Typical 5% Output Current Accuracy 2 N/C Single Pin for On/Off and Brightness Control by DC Voltage or GND 7 EP PWM Signal 3 6 GND L X Recommended Analog Dimming Range: 5% to 100% Soft-Start 4 V 5 L SET X High Efficiency (Up to 97%) LED Short Protection MSOP-8EP Inherent Open-Circuit LED Protection RS Short Protection Applications Over Temperature Protection (OTP) Up to 1MHz Switching Frequency LED Retrofit for Low Voltage Halogen Pb-Free TSOT25, SOT89-5 and MSOP-8EP Packages Low Voltage Industrial Lighting Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) LED Backlighting Halogen and Antimony Free. Green Device (Note 3) Illuminated Signs For automotive applications requiring specific change External Driver with Multiple Channels control (i.e. parts qualified to AEC-Q100/101/200, PPAP capable, and manufactured in IATF 16949 certified facilities), please contact us or your local Diodes representative. 1 AL8861 Typical Applications Circuit D1 Rs VIN (4.5V-40V) ISENSE VIN AL8861 L1 C1 VSET LX GND Pin Descriptions Pin Number Pin Name Function TSOT25/ MSOP-8EP SOT89-5 1 5, 6 L Drain of NDMOS switch. X 2 2, 3 GND Ground (0V) Multi-Function On/Off and Brightness Control Pin: Leave floating, internal current source (typical 1.4A) will pull up this pin to 4.5V Drive to voltage below 0.2V to turn off output current Drive with DC voltage (0.3V < V < 2.5V) to adjust output current from 0 to 100% of SET IOUTNOM. Linear adjustment ranges from 5% to 100% of IOUTNOM 3 4 V SET Drive with PWM signal from open-collector or open-drain transistor, to adjust output current. Linear adjustment ranges from 1% to 100% of IOUTNOM for f < 500Hz Connect a capacitor from this pin to Ground to increase soft-start time. (Default soft-start time = 0.1ms. Additional soft-start time is approximately 1.5ms/1nF) Connect resistor RS from this pin to VIN to define nominal average output current. 4 1 ISENSE I = 0.1/R OUTNOM S Input voltage (4.5V to 40V). Decouple to Ground with 10F or higher X7R ceramic capacitor 5 8 V IN close to device. 7 N/C No Connection 2 of 18 AL8861 November 2020 Diodes Incorporated www.diodes.com Document number: DS39435 Rev. 4 - 2