2010-01-12

6

BCR402W

Application Circuit:

supply voltages >18V

Standard Application Circuit:

B C R 402W

Vdrop

Rext

3

4

2

1

+V s

Rsense

(optional)

Vsupply

BCR401W

BCR402W

LEDs

Vs

GND

Rext

Iout

LEDs

Application hints

BCR402W serves as an easy to use constant current source for LEDs. In stand alone

application an external resistor can be connected to adjust the current from 20 mA to 60 mA.

Rext can be determined by using the diagram 'Output current versus external resistor',

or by refering to diagram 'Output current versus reference voltage'. Look for your desired

output current on the y axis and read out the corresponding Vdrop. Calculate Rext:

Rext = Vdrop / (Iout -(Vdrop/Rint))

Please take into account that the resulting output currents will be slightly lower due to the

self heating of the component and the negative thermal coefficient.

• AN077 gives hints to thermal design

• AN182 provides a guideline for replacing resistor biasing with BCR401W / BCR402W

constant current sources in 12 & 24V striplight applications