Buck LED driver internally generates PWM dimming

22nd April 2016

Nat Bowers

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Datasheet

Offering constant-current output to drive high-power LEDs in automotive applications, two single-IC switching regulators have been introduced by Allegro MicroSystems Europe. These devices are the industry’s first, according to the manufacturer, to allow LED dimming without the need for local MCU, timer-based or PWM dimming control.

Allegro’s A6214 and A6216 integrate a high-side N-channel DMOS switch for DC-to-DC step-down (buck) conversion. A true average current is output using a cycle-by-cycle, controlled on-time method. Combined with automotive-grade quality and feature-rich functionality, a host of safety and robust protection features makes the A6214 and A6216 devices ideal for automotive lighting where high quality and reliability are essential.

User-selectable output current provides system design and application flexibility and automatic output voltage adjustment based on the number of LEDs in a single string ensures optimal system efficiency. An internal 5V, 10mA LDO provides added flexibility and system cost savings for driving local circuitry if required.

LED dimming is accomplished by a direct logic input PWM signal at the enable pin. An analogue dimming input can be used to calibrate the LED current or implement thermal foldback in conjunction with an external NTC thermistor. The A6216 has the unique capability to generate its own PWM dimming frequency and duty cycle in stand-alone mode that provides LED light dimming control without the need for an MCU or timer.

Allegro’s A6214 is provided in a compact 10-pin narrow SOIC package (suffix LK). The A6216 is available in a 16-pin TSSOP package (suffix LP), both with exposed pad for enhanced thermal dissipation. Both are lead-free, with 100% matte-tin lead frame plating.