Automotive-compliant buck LED drivers simplify LED lamp design

Two automotive-compliant DC/DC buck converters have been designed by Diodes for driving single LEDs and multiple LED strings in and around vehicles.

The AL8843Q and AL8862Q can be used in daytime running lights (DRL), which many manufacturers now offer as standard, as well as fog lights, indicator lights and brake lights.

They have a supply voltage from 4.5V and up to 40V (AL8843Q) and 55V (AL8862Q), to withstand even severe voltage variations, such as load dumps during low cranking or stop-start operation, without suffering any corresponding degradation in the LED drive current.

A high level of integration minimises the bill of materials. Both parts feature an integrated power MOSFET (40V/0.2Ohm for the AL8843Q and 55V/0.4Ohm for the AL8862Q). Both also feature hysteretic-mode buck LED driver control, which simplifies the feedback loop enabling engineers to realise highly stable buck converter designs using just four external components.

Differentiating features for the AL8843Q include an input voltage range of 4.5V to 40V and 3A output current, while the AL8862Q can operate at between 5V and 55V input voltage, delivering up to 1A at the output. Both parts support full scale (0 to 100 per cent) PWM dimming, controlled with either an analogue input between 0.4V and 2.5V or a PWM signal generated by an external microcontroller or host processor. Safety features include over-temperature protection as well as LED short- and open-circuit protection. The AL8862Q incorporates an open-drain fault indication pin, which is asserted low to report faulty conditions.

The AL8843Q and AL8862Q in SO-8EP are qualified to AEC-Q100 Grade 1.

Diodes manufactures and supplies application specific standard products within the broad discrete, logic, analogue and mixed-signal semiconductor markets. The company serves the consumer electronics, computing, communications, industrial, and automotive markets with a portfolio of diodes, rectifiers, transistors, MOSFETs, protection devices, function-specific arrays, single gate logic, amplifiers and comparators, Hall-effect and temperature sensors, power management devices, including LED drivers, AC/DC converters and controllers, DC/DC switching and linear voltage regulators, and voltage references along with special function devices, such as USB power switches, load switches, voltage supervisors, and motor controllers. Diodes also has timing, connectivity, switching, and signal integrity solutions for high-speed signals.

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