Datasheet

ILD4035
350 mA Step Down LED Driver
Basic Application Information
Data Sheet 19 Revision 2.0, 2011-08-17
6.3 Temperature Protection Circuit
ILD4035 incorporates a temperature protection circuit referring to the junction temperature of ILD4035. The higher
the junction temperature of ILD4035 the lower the current of the LEDs. This feature helps to reduce the power
dissipation of ILD4035 and the LEDs. Yet still the product specific maximum ratings for junction temperature need
to be observed to avoid a permanent damage of the devices.
ILD4035 has been characterized on ILD4035/4001 application board heated from the backside without additional
air flow on the circuit board surface besides natural convection. Design and layout of the circuit board as well as
the air flow influence the thermal resistance junction to ambient
R
thJA
of ILD4035 and thus its junction temperature.
Below figures show the LED current versus soldering point temperature
T
S
.
6.4 Switching Parameters
For all shown parameters ILD4035 has been measured on evaluation board ILD4035/4001 at T
A
= 25 °C. Used
LEDs have a typical forward voltage
V
fLED
of 3 V. For details see application note AN215 (Driving 1W LEDs with
ILD4035) or visit our web site http://www.infineon.com/lowcostleddrivers.
LED current versus
T
S
, V
S
= 12 V LED current (relative) versus T
S
, V
S
= 12 V
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
40 50 60 70 80 90 100 110 120 130
I
LED
[A]
T
S
[°C]
303 mΩ, 100 μH
333 mΩ, 100 μH
600 mΩ, 100 μH
1200 mΩ, 220 μH
70
80
90
100
110
40 50 60 70 80 90 100 110 120 130
I
LED
[%]
T
S
[°C]
303 mΩ, 100 μH
333 mΩ, 100 μH
600 mΩ, 100 μH
1200 mΩ, 220 μH