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High-brightness LED driver powers 15W systems

Posted: 30 Oct 2007 ?? ?Print Version ?Bookmark and Share

Keywords:high-brightness LED drivers? power dissipation? PFET? PWM?

National Semiconductor's two new high-brightness LED drivers in its PowerWise product family, the LM3401 and LM3405A, are suited to industrial and automotive tasks and general lighting/signage. Each touts a wide input voltage range, constant-current operation for better regulating LED brightness, and low feedback voltage to minimize power dissipation.

The LM3401 switching controller, rated at a 4.5-35V input, drives an external PFET that can provide 1A at constant-current (within 6 percent) to a high-power LED string. The hysteretic window is adjustable for flexibility in component selection and overall design simplicity. No external compensation is required. Its design eliminates the need for an output capacitor. Offered in an 8-pin mini SOIC package, the LM3401 has programmable overcurrent voltage protection and a DIM input pin for pulse-width-modulation (PWM) inputs to control dimming.

The LM3405A buck LED driver, with a 3-22V input, is a 1.6MHz device that can regulate from a loosely coupled 12V AC rail that's typical of industrial and commercial lighting applications. Offered in a 6-pin SOT-23 package, the constant-current chip delivers up to 1A (drives up to five high-brightness LEDs). The LM3405A also includes an EN/DIM pin for PWM dimming.

The LM3401 is priced at 75 cents each and the LM3405A is $1.30 in 1,000-unit quantities.

- Vince Biancomano
Power Management DesignLine




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