BCR420UFD / BCR421UFD

Document number: DS38588 Rev. 3 - 2

9 of 13

www.diodes.com

January 2018

© Diodes Incorporated

BCR420UFD / BCR421UFD

(Optional)

Application Information

The BCR420/1 are designed for driving low current LEDs with typical

LED currents of 10mA to 350mA. They provide a cost-effective way for

driving low current LEDs compared with more complex switching

regulator solutions. Furthermore, they reduce the PCB board area of the

solution as there is no need for external components like inductors,

capacitors and switching diodes.

Figure 1 shows a typical application circuit diagram for driving an LED

typically 95

Ω, which in the absence of an external resistor, sets an LED

be increased to a desired value by choosing an appropriate external

(Optional)

Figure 1 Typical Application Circuit for

Linear Mode Current Sink LED Driver

Two or more BCR420/1s can be connected in parallel to construct

higher current LED strings as shown in Figure 2. Consideration of the

expected linear mode power dissipation must be factored into the

design, with respect to the BCR420/1

’s thermal resistance. The

maximum voltage across the device can be calculated by taking the

maximum supply voltage and subtracting the voltage across the LED

string.

(Optional)

(Optional)

As the output current of BCR420/1 increases, it is necessary to provide

appropriate thermal relief to the device. The

power

dissipation

supported by the device is dependent upon the PCB board material, the

copper area and the ambient temperature. The maximum dissipation

the device can handle is given by:

Figure 2 Application Circuit for Increasing LED Current

Refer to the thermal characteristic graphs on Page 4 for selecting the

appropriate PCB copper area.