Datasheet

10

Rev. 1.0, 2007-03-20

TLE4309

4. Calculating the maximum power dissipation:

For calculating the maximum power dissipation, the minimum forward voltage sum of the

LEDs connected in series

V

voltage

V

current

I

calculates:

P

With assuming a maximum current consumption of 15 mA @

I

the

maximum power dissipation for the example is 1.28 W.

5. Thermal Resistance needed:

The thermal resistance from junction to ambient

R

R

With allowing a junction temperature of 150 °C, the

R

be 50 K/W.

In case some copper area on the PCB is used as a heat sink, the area needed is

approximately 6 cm

several via holes to the GND-layer or to a heatsink area on the PCB backside help to

distribute the heat.

For additional information on the thermal resistance see Infineon’ s special subject book

“Thermal Resistance - Theory and Practice” including extended package information.