DIODES AL8861QEV1 EVB User Guide

: June 4, 2024
: DIODES

Table of Contents

DIODES® AL8861QEV1 EVB User Guide
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DIODES® AL8861QEV1 EVB User Guide

General Description

The AL8861Q is a hysteresis mode DC-DC step-down converter, designed for driving single or multiple series connected LEDs efficiently from a voltage source higher than the LED voltage. The device can operate with an input supply voltage from 4.5V to 40V and provide an externally adjustable output current up to 1.5A for MSOP-8EP package. Depending upon supply voltage and external components, this converter can provide up to 40 watts output power.

The AL8861Q integrates the power switch and a high-side output current sensing circuit, which uses an external resistor to set the nominal average output current. 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 PWM signal.

The soft-start time can be adjusted by an external capacitor from the 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 power consumption.

The AL8861Q has been qualified to AECQ100 Grade 1 and is Automotive Grade supporting PPAPs.

Applications

Automotive Interior LED Lamps
Automotive Exterior LED Lamps

Key Features

AEC-Q100 Grade 1 Qualified
Wide Input Voltage Range: 4.5V to 40V
Output Current Up to 1.5A
Internal 40V NDMOS Switch
Typical 5% Output Current Accuracy
Single Pin for On/Off and Brightness Control by DC Voltage or
PWM Signal
High Efficiency (>95%)
LED Short-Circuit Protection
Inherent LED Open-Circuit Protection
Over Temperature Shutdown
Up to 1MHz Switching Frequency
Pb-Free MSOP-8EP Packages
Totally Lead-Free & Fully RoHS Compliant
Halogen and Antimony Free. “Green” Device

AL8861QEV1 Specifications

Evaluation Board

Connection Instructions

Power Supply Input: 4.5~40VDC (VIN, GND)
VSET: 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.
PWM Signal Input: Remove C3, apply PWM signal to VSET (VSET, GND)
Analog Signal Input: Connect 100nF capacitor to C3, apply analog signal to VSET (VSET, GND)
LED A: LED A connects to the external LED anode
LED K: LED K connects to the external LED cathode

Evaluation Board Schematic

Figure 3 Evaluation Board Schematic

Evaluation Board Layout

Quick Start Guide

By default, the evaluation board is preset at 1.5A LED Current by R1 and R2.
Non-dimming operation: Leave VSET pin floating for normal operation.
Power Supply: Connect the 5~40VDC to VIN & GND pin to supply the system and AL8861Q.
PWM Dimming: Remove C4; apply a PWM signal (low level < 0.3V and high level > 2.5) to VSET pin to dim the LEDs. The recommended PWM signal frequency is from 100Hz to 1kHz, and the PWM duty is from 1% to 100%.
Analog Dimming: Connect 100nF capacitor to C3; the VSET pin may be driven between 0.3V and 2.5V adjusting the output current from 5% to 100% of ILED.

Bill of Material

Note: The component part numbers are correct at the time of publication. Diodes Inc reserves the right to substitute other parts where necessary, without further notification.

Functional Waveforms

Functional Waveforms Continued

Functional Data Curves

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