A6271: Automotive, High-Current LED Controller


The A6271 is a DC-DC converter controller, providing a programmable constant-current output for driving high-power LEDs in series. The 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, and buck (ground-referenced switch).

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 carefully 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.

The 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 overvoltage protection ensures no maximum voltage rating violations, even under a single point failure of the programmable-output overvoltage protection circuit. Other protection features include: LED overload (boost), output undervoltage (buck or buck-boost), input supply (VIN) undervoltage, 5 V Regulator (VREG) output undervoltage, high-side supply (PWM PMOS) undervoltage, and thermal protection.

These parts are in production but have been determined to be NOT FOR NEW DESIGN. This classification indicates that sale of this device is currently restricted to existing customer applications. The device should not be purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available.

Date of status change: December 14, 2017

Recommended Substitutions: A6271-1

Top Features

  • Automotive AEC-Q100 qualified
  • Constant-current LED drive
  • 4.5 to 50 V supply
  • 53.3 V maximum LED string voltage
  • Boost, buck-boost, and buck switching converters
  • Programmable switching frequency 70 kHz to 700 kHz
  • PWM-controlled PMOS driver allows accurate LED current control at low duty cycles
  • Dimming via external PWM, internal PWM and/or analog dimming
  • Frequency dither scheme for effective spread spectrum to reduce EMI
  • Comprehensive fault protection and Fault Flag

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
A6271KLPTR-T 16-lead TSSOP -40°C to 125°C Yes View Data Not for new design Contact your
local sales rep
Distributor Stock

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.



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