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02-13-2018

Constant-Current LED Drivers now Offered in Low-Profile DFN Package Suitable for Edge Lighting

Diodes » BCR420UFD, BCR421UFD

Diodes Incorporated announced the BCR420UFD and BCR421UFD. In response to growing demand for smaller LED lighting installations that also provide high efficiency and ultra-low EMI, Diodes Incorporated has extended its popular BCR420U and BCR421U families of linear LED drivers to include these devices in the ultra-low profile DFN2020 package, making them well-suited for 12 V and 24 V LED edge-lighting applications.

Diodes - BCR420UFD, BCR421UFD

The primary benefits of LED lighting, namely longer lifetime and higher efficiencies, means there is growing demand for more varied and less intrusive solutions. This includes fittings that emit light from the edges as opposed to vertically. In order to meet this demand, manufacturers are looking for solutions that support a thinner overall profile. At just 0.6 mm in height, the DFN2020 package is uniquely suited to edge lighting.

Like other members of the BCR4xxU series, the new devices can deliver an adjustable constant current between 10 mA and 200 mA (BCR420UFD) or 350 mA (BCR421UFD) with ±10% tolerance, which in the case of the BCR421UFD can be controlled using a PWM signal of up to 25 kHz and a duty cycle of 1% to provide LED dimming functionality. Both devices include a negative temperature coefficient, which lowers the LED driver current as the internal temperature rises, thereby protecting and extending the lifetime of the LEDs. In addition, the linear topology used is based on an NPN emitter-follower with emitter resistor, which means the devices exhibit virtually no EMI, making them well-suited for sensitive applications such as medical lighting.

With a wide operating voltage range of between 1.4 V and 40 V, total power dissipation of up to 1.7 W, the devices can be used to drive larger strings of LEDs while still providing sufficient protection from transients in a 24 V system. Designed as monolithic solutions, the devices integrate transistors, diodes and resistors in a single package measuring just 0.6 mm high. This is much thinner than the standard SOT26 package, allowing engineers, architects and lighting designers to develop LED fitments with a much lower overall profile, for a wider range of applications. Edge lighting is now being specified in areas such as emergency, mood or decorative lighting, but is equally applicable in medical, industrial and commercial environments.

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