Linear current regulators for automotive LED lighting

Two AEC-Q100 qualified linear current regulators for driving automotive LED arrays have been announced by Allegro MicroSystems.

The adjustable low-EMI ICs integrate a pre-regulator gate drive to control an external P-channel MOSFET, which is said to extend the output power capability of a linear LED driver by moving the power losses to an external power FET.

The A6274 and A6284 devices sink up to 60mA or 120mA respectively from six LED pins, and can be paralleled to drive higher current LED strings of up to 720mA. In addition, the devices are claimed to be configurable in parallel for large lighting systems.

The ICs include an internal pulse width modulation (PWM) dimming circuit that is programmed by external resistors for PWM duty cycle and frequency. This eliminates the need for a PWM signal usually provided by a local MCU or 555 timer. Alternatively, an external PWM signal can be applied by an existing control module. The devices can be configured to change between full and dim modes for bi-level operation in applications, including stop/tail rear combination lamps or daytime running lights.

Both ‘latching’ and ‘unlatched’ versions are offered, to align fault detection and protection schemes with global standards.

Both devices are supplied in a 20-lead, eTSSOP package with exposed pad for enhanced thermal performance.

Peggy Lee