TLE4309GXT Infineon Technologies, TLE4309GXT Datasheet - Page 9

• Manufacturer Part Number: TLE4309GXT
• Manufacturer: Infineon Technologies

Specifications of TLE4309GXT

• Operating Supply Voltage (typ): 5/9/12/15/18V
• Number Of Segments: 3
• Operating Temperature (min): -40C
• Operating Temperature (max): 150C
• Operating Temperature Classification: Automotive
• Mounting: Surface Mount
• Operating Supply Voltage (min): 4.5V
• Operating Supply Voltage (max): 24V
• Lead Free Status / Rohs Status: Compliant

Application Note: Thermal Considerations
By describing an example, this section shows how the power dissipation and the needed
thermal resistance can be estimated.
For a typical application circuit as shown in Figure 1, the following parameters shall
apply:
•
•
•
•
•
•
•
1. Selecting the reference resistor:
The reference resistor
the value from the typical performance graph “Output Current versus Reference
Resistor” on Page 7. In order to obtain a LED forward current of
shows an reference resistor of
2. Verifying the minimum supply voltage:
In order to be able to drive the LEDs with a constant current, the minimum supply voltage
needed is:
whereas
series,
Since the power dissipation is low at a small voltage drop accross the regulator,
V
a minimum supply voltage of 11 V is sufficient for the example given above.
3. Determining the minimum and maximum LED forward current:
The TLE4309 has an accuracy of < 4 %. With a reference resistor of
output current
1) This information is given as a hint for the implementation of the device only and shall not be regarded as a
Datasheet
dr
description or warranty of a certain functionality, condition or quality of the device.
Number of LEDs in series: 3
LED current desired:
LED minimum forward voltage:
LED maximum forward voltage:
Supply minimum DC voltage:
Supply maximum DC voltage:
Maximum ambient temperature:
= 0.35 V is assumed. The maximum reference voltags is
V
V
I,MIN
dr
V
the dropout voltage and
F,MAX,total
=
I
V
Q
F,MAX,total
will be between 251 mA and 272 mA.
is the maximum forward voltage sum of the LEDs connected in
R
REF
I
+
F
V
= 260 mA
can be selected by using the formular on page 2 or by taking
dr
+
R
REF
V
V
V
REF
I,MIN
V
V
I,MAX
V
T
= 0.68 .
F,MIN
REF
F,MAX
a,max
= 11.0 V
= 13.0 V
the reference voltage.
= 3.0 V
= 85 °C
= 3.4 V
9
1)
V
REF
I
F
= 185mV. Therefore,
= 260 mA, the graph
Rev. 1.0, 2007-03-20
R
REF
= 0.68
TLE4309
the