DIODES AL8862QEV2 Medium and Low Voltage DC-DC LED Drivers User Guide

DIODES AL8862QEV2 Medium and Low Voltage DC-DC LED Drivers

General Description

The DIODES AL8862Q is a step-down DC-DC converter designed to drive LEDs with a constant current. The AL8862Q operates with an input supply voltage from 5V to 55V and provides an externally adjustable output current up to 1A. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors. The AL8862Q switches at frequencies up to 1MHz. This allows for the use of smaller size external components, hence minimizing the PCB size.
The AL8862Q integrates the power switch and a high-side output current sensing circuit. The maximum output current of AL8862Q is set via an external resistor connected between the VIN and SET input pins. Dimming is achieved by applying either a DC voltage or a PWM signal at the CTRL input pin. The softstart time can be adjusted using an external capacitor from the CTRL pin to the ground. An input voltage of 0.3V or lower at CTRL pin will shut down the power switch.
The AL8862Q is qualified to AEC-Q100 Grade 1 and is automotive grade to support PPAPs.

Applications

• Automotive interior LED lamps
• Automotive exterior LED lamps

Key Features

• 2.0V to 60V Wide Input Voltage Range
• Wide Input Voltage Range: 5V to 55V
• Output Current up to 1A
• Internal 55V NDMOS Switch
• Typical 4% Output Current Accuracy
• Single Pin for On/Off and Brightness Control by DC Voltage or
• PWM Signal
• High Efficiency (Up to 97%)
• Fault Status Indication for Abnormal Operation
• LED Short-Circuit Protection
• Inherent Open-Circuit LED Protection
• Current-Sense Resistor Short-Circuit Protection
• Overtemperature Shutdown
• Up to 1MHz Switching Frequency
• SO-8EP Package Available in Green Molding Compound (No Br, Sb)

AL8862QEV2 Specifications

EVB Physical Picture

Figure 1. Top View

Figure 2. Bottom View

Connection Instructions and Quick Start Guide

1. Connect LED string anode end to “LEDA” and connect LED string cathode end to “LEDK”.
2. Power Supply Input: 4.5~16VDC, connect two DC line wires to the BAR+ and BAR-terminals on the evaluation board. It’s better to set at least 3V voltage gap between input and output.
3. For PWM dimming operation: supply a 0-3.3V 200Hz~2 kHz signal between DIM & GND.
4. The LED current of demonstration board is preset at 1A.
5. Ensure that the DC source is switched OFF or disconnected before soldering or connecting.
6. Ensure that the area around the board is clear and safe, and preferably that the board and LEDs are enclosed in a transparent safety cover.
7. Turn on the main switch. LED string should light up.

Evaluation Board Schematic

Figure 3. Evaluation Board Schematic

Evaluation Board Layout

Figure 4. PCB Top Layer

Figure 5. PCB Bottom Layer

Bill of Material

SMT
L2| 744373965150,15uH, Isat=10.2A, 13.65×12.5×6.2mm, AEC-Q200, Würth Elektronik| SMT
D2,D3| Diode, SBR8M100P5Q-13,8A,100V, AEC-Q101 Qualified, DIODES| POWER DI5
DIM, FAULT,GND| Connector, Orange color| DIP
LEDK| Connector, Black color| DIP
BAR-| Connector, White color| DIP
LEDA, BAR+| Connector, Red color| DIP

System Performance

PWM Dimming Curve
Test @VIN=12V, LED voltage=5.3V

Waveforms

Turn ON@12V

Figure 6. Startup @ Output =1 LED

Figure 7. Startup @Output =3 LEDs

Turn OFF:

Figure 8. Turn off @Output =1 LED

Figure 9. Turn off @Output =3 LEDs

Stable waveforms:

Figure 10. @Output =1 LED

Figure 11. @Output =3 LEDs

PWM Dimming Waveforms, PWM duty =50%

Figure 12. Output =1 LED

Figure 13. Output =3 LEDs

Thermal Test

IC Tc = 48.8C degree @ ambient = 23C degree, temperature rise is 25.8C degree.
Tested in VIN=13.5V, VLED=9.5V.

Conductive Emission Test

Tested in VIN=13.5V, loading with 3pcs LED (Vo =9.5V)

Frequency| MaxPeak| Average| Limit| Margin| Meas._Time| Bandwidth| Line| Corr.
---|---|---|---|---|---|---|---|---
MHz| dBμV| dBμV| dBμV| dB| ms| kHz| | dB
5.95| —| 35.38| 45.00| 9.62| —| —| Single Line| 0.1
5.955| 37.50| —| 65.00| 27.50| —| —| Single Line| 0.1
31.800| —| 23.56| 36.00| 12.44| —| —| Single Line| 0.2
53.000| 26.50| —| 46.00| 19.50| —| —| Single Line| 0.2
75.800| —| 23.68| 29.98| 6.30| —| —| Single Line| 0.4
75.800| 29.09| —| 46.00| 16.91| —| —| Single Line| 0.4

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