Linear current regulators are adjustable for automotive lighting
Two adjustable linear current regulators for driving automotive LED arrays are announced by Allegro MicroSystems Europe. The AEC-Q100-qualified A6274 and A6284 include new features, designed to enhance the existing family of linear LED drivers.
The low-EMI ICs integrate an optional pre-regulator gate drive to dynamically and linearly control an external P-channel MOSFET, which extends the output power capability of a linear LED driver by moving most of the power losses to an external power FET. This eliminates the need for DC/DC switching and its associated inductor, diode and higher EMI. The ICs 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. Multiple ICs can be configured in parallel for large lighting systems.
LED light output can be adjusted by PWM dimming. The ICs include an internal PWM dimming circuit that is programmed by external resistors for 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. The devices can be configured to change between full and dim modes for bi-level operation (often needed for stop/tail rear combination lamps, or daytime running lights).
Latching and unlatched versions are offered. Both devices are supplied in a 20-lead, eTSSOP package with exposed pad for enhanced thermal performance.