Allegro MicroSystems has introduced a new DC-DC converter controller, providing a programmable constant current output for driving high power LEDs in series. Allegro's A6271 controller is based on a programmable fixed frequency, peak current mode control architecture. The DC-DC converter can be configured in a myriad of different switching configurations including boost, buck-boost, SEPIC and buck (ground referenced switch). This new device is designed for automotive exterior lighting applications to include high power LED lighting systems, fog lights, reversing lights, daytime running lights (DRLs), position lights, and headlights.
The A6271 provides a cost-effective solution using an external logic-level MOSFET and minimum additional external components. The maximum LED current is set with a single external sense resistor and can be accurately modulated using a current reference input (analog control). External PWM dimming is possible via the PWMIN input, which also provides a shutdown mode. As an alternative, an internal PWM dimming circuit can be used by programming the PWMIN and DR pins. Either PWM scheme controls the PWMOUT output which drives an external p-channel MOSFET connected in series with the LED string. This MOSFET is also used to isolate the load during certain fault conditions, including output shorts to ground.
The A6271 has been designed to minimize electromagnetic emissions through distributed decoupling and an externally programmable frequency dither circuit configured for the EMI specification CISPR 25. It is also possible to program the fundamental switching frequency below 150 kHz where most EMI standards begin.
Allegro's A6271 has a comprehensive set of integrated protection features to protect the IC, the LED driver system, and the LED string against faults. Fixed output over voltage protection ensures no maximum voltage rating violations even under a single point failure of the programmable output over voltage protection circuit. Other protection features include; LED over load (boost, SEPIC), output under voltage (buck or buck-boost), input supply (VIN) under voltage, 5 V Regulator (VREG) output under voltage, high side supply (PWM PMOS) under voltage, and thermal protection.
The A6271KLPTR-T is available in a 16-pin eTSSOP (suffix LP) package with exposed thermal pad for enhanced power dissipation. It is priced at $1.89 in quantities of 1,000.