Diodes' adjustable current regulator simplifies LED drives

     Diodes Corporation, a leading global manufacturer and supplier of high quality application-specific standard products to the broad discrete, logic and analog semiconductor markets, introduces the BCR420U and BCR421U. These constant-current regulators (CCRS) provide an easy way to drive low-power linear strips. Target applications are those that benefit from the improved efficiency, flexibility and longer life provided by leds as an emerging lighting source. These include LED strips for mood lighting, emergency and advertising signage and lighting for retail refrigeration and vending machines.

     The BCR420U and BCR421U allow optimized LED currents to be set to give a uniform brightness and extend the life of the LED. Support for adjustable currents from 10mA to 350mA allows applications based on platform designs on a single device that can use multiple LED strings, greatly easing the entire qualification process for manufacturers. These LED drivers also enhance system reliability with the monolithic integration of transistors, diodes and resistors both simplifying system design and reducing the number of components.

     The negative temperature coefficient, which reduces the output current as the temperature increases, allows the current to be distributed between two or more of these CCR devices. This allows them to be connected in parallel to create a higher current output without the risk of thermal runaway. The maximum rated input at 40V provides ample room for expansion of the transient power supply voltage and allows short circuit failures in long string leds. With its low side driver configuration, the BCR421U has an enable feature that can adjust the increase of the optical output level using the PWM input signal. Both devices are available in the SOT2 6 package, providing pin compatibility with other sources.