Power Electronics

Driver ICs Power LEDs to 5 W

National Semiconductor’s LM3402, LM3404 and LM3405 family of light-emitting diode (LED) drivers are designed to power the 1-W to 5-W, high-brightness LEDs. These LED drivers provide a constant current to regulate the LED brightness and low feedback voltage to minimize power dissipation.

"National already offers a wide portfolio of LED drivers designed for low-power portable applications such as those in cell phones and PDAs," said Mal Humphrey, product line director for the Power Management Group at National Semiconductor. "This new family of products extends that portfolio, using our higher voltage and current capabilities to address the high-brightness LED market as well."

Optimized for 1-W LEDs, National offers two versions of the LM3402 LED driver that provide wide input voltage ranges of either 6 V to 42 V, or 6 V to 75 V. For 3-W and 5-W LEDs, the LM3404 and LM3405 have additional output current drive capability.

The LM3402 is a compact, constant-current buck regulator with up to 95% efficiency that drives up to 525 mA of current. Offered in an 8-pin mini SOIC package, the LM3402 has an enable pin that also can be used for dimming via pulse-width modulation (PWM) inputs and a reduced feedback of 0.2 V for current sensing. The LM3402's input voltage ranges from 6 V to 42 V. For higher input voltages, the LM3402HV offers the same features and a 6-V to-75-V voltage range.

Offered in an 8-pin SOIC narrow package, the LM3404 and LM3404HV share the same functionality as the LM3402 and LM3402HV, but have the ability to drive currents up to 1.2 A. These products are well-suited to power 3-W and 5-W LEDs at current levels of 700 mA or 1 A, respectively.

Offered in an 8-pin mini SOIC package and a tiny 6-pin SOT-23 package, the LM3405 constant-current buck regulator delivers up to 1 A of current to drive 3-W or 5-W LEDs. With a 0.2-V reference voltage for constant-current feedback control and a switching frequency that is internally set to either 550 kHz or 1.6 MHz, the LM3405 provides a simple, highly-efficient solution for driving LEDs. In addition, the LM3405 has an input voltage range of 3 V to 22 V, is internally compensated and has an En/Dim pin for PWM dimming.

The LM3402 and LM3402HV are available now in production quantities. Samples of the LM3404 and LM3404HV are available now and production quantities will be available in November. Samples of the LM3405 will be available in November and production quantities will be available in January 2007. Prices for these LED drivers start at $1.35 for the LM3402 and $1.65 for the LM3402HV in 1000-unit quantities.

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