BCR405U データシートの表示（PDF） - Infineon Technologies

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BCR405U

LED Driver

Infineon Technologies 

Application circuit:

Stand alone current source

BCR 405U

+Vs

4

Rext

(optional)

6

Vdrop

BCR405U

Application circuit:

Boost mode current source with

external power transistor

BCR 405U

+Vs

4

Rext

(optional)

6

Vdrop

ILED

1

2,3,5

Is

Iout

1

2,3,5

Is

Iout R1

R2

Application hints

BCR405U 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 50 mA to 65 mA.

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

or by refering to diagram 'Reference voltage versus output current'. Look for your desired

output current on the x 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.

In boost mode configuration the LED current can be extended to drive high power LEDs.

Select the power trasistor according the power dissipation and output current requirements.

(e.g. BC817SU or BCX68-25, etc.) Dimension R2 to reduce the transistor current transfer

ratio to 20 ... 50. For ILED / Iout =50 e.g. ILED= 350 mA, Iout is 7 mA.

R2 = VbeON / Iout.

Dimension R1 for minimum supply voltage condition:

R1 = (Vsmin -1.4V -VbeON)/ Iout.

Please visit our web site for application notes: www.infineon.com/lowcostleddriver

• AN077 gives hints to thermal design

• AN097 helps in case of high supply voltages

• AN101 gives an overview to LED biasing

7

2009-07-31

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