2009-11-13

6

BCR401R

Application Circuit:

supply voltages >18V

Standard Application Circuit:

V d r o p

B C R 4 0 1 R

R e x t

3

4

2

1

+ V s

I s

I o u t

Rsense

(optional)

Vsupply

BCR401R

BCR402R

LEDs

Vs

GND

Rext

Iout

LEDs

Application hints

BCR401R 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 10 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.

• AN066 explains the basic concept

• AN077 gives hints to thermal design

• AN159 provides information how to add a power transistor to increase the output current