Adjustable linear LED drivers slash EMI for car lighting
Article By : Allegro MicroSystems
The low-EMI A6274 and A6284 from Allegro pack an optional pre-regulator gate drive to control an external P-channel MOSFET, boosting the output power capability of a linear LED driver.
Allegro MicroSystems has introduced a couple of adjustable linear current regulators geared for car LED arrays. The low-EMI A6274 and A6284 incorporate an optional pre-regulator gate drive to dynamically and linearly control an external P-channel MOSFET, extending the output power capability of a linear LED driver by moving most of the power losses to an external power FET, noted the company. This cuts the need for a DC/DC switching solution and its associated inductor, diode and higher EMI.
The Linear LED drivers sink up to 60mA (A6274) or 120mA (A6284) from each of six LED pins, and may also be paralleled to drive higher current LED strings for a total of up to 720mA. In addition, multiple ICs can be configured in parallel for large lighting systems.
LED light output can be adjusted by PWM dimming, and the ICs provide an internal PWM dimming circuit that is programmed by external resistors for accurately controlled PWM duty cycle and frequency. This eliminates the requirement for a PWM signal usually provided by a local microcontroller or 555 timer. Alternatively, an external PWM signal can be applied in particular if already available by an existing control module. The devices can be configured to change between full and dim modes for bi-level operation, as often needed for stop/tail rear combination lamps (RCL) or daytime running lights (DRL).
Both “latching” and “unlatched” versions are offered, to align fault detection and protection schemes with global standards for automotive external lighting applications.
The AEC-Q100 qualified-devices are supplied in a 20-lead, eTSSOP package (suffix “LP”) with exposed pad for enhanced thermal performance.
