TLE4309 Infineon Technologies Corporation, TLE4309 Datasheet - Page 10

• Manufacturer Part Number: TLE4309
• Description: Adjustable Linear Low Dropout Led Driver
• Manufacturer: Infineon Technologies Corporation

4. Calculating the maximum power dissipation:
For calculating the maximum power dissipation, the minimum forward voltage sum of the
LEDs connected in series
voltage
current
calculates:
With assuming a maximum current consumption of 15 mA @
maximum power dissipation for the example is 1.28 W.
5. Thermal Resistance needed:
The thermal resistance from junction to ambient
With allowing a junction temperature of 150 °C, the
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.
Datasheet
P
R
I
V
Q,MAX
D,MAX
th,j-a
I,MAX
= (
= (
, the IC current consumption
needs to be considered. Hence, the maximum power dissipation
T
V
j,max
I,MAX
2
(board in horizontal position, no airflow). If the area is not available,
-
T
-
a,max
V
F,MIN,total
) /
V
F,MIN,total
P
D,MAX
) *
I
Q,MAX
(= No. of LEDs *
10
+
I
q,MAX
V
I,MAX
R
th,j-a
, as well as the the maximum output
R
*
th,j-a
I
calculates:
q,MAX
V
needed in our example would
F,MIN
) , the maximum supply
Rev. 1.0, 2007-03-20
I
Q
= 260 mA, the
TLE4309
P
D,MAX