TLE4309 Infineon Technologies Corporation, TLE4309 Datasheet - Page 2

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

Circuit Description
An external shunt resistor in the ground path of the connected LEDs senses the LED
current. A regulation loop maintains the voltage drop across the shunt resistor at a
constant level. Selecting the shunt resistance permits to adjust the appropriate constant
current . The output current calculates
where
equation applies in a range of 0.39
shown as a function of the reference resistance.
Figure 1
During operation, the LED brightness is modifiable by adjusting the duty cycle at the
PWM/EN input. This allows to dim the LEDs during operation or adapt the output current
to different LED luminosity classes.
A low signal at the PWM/EN input sets the IC into sleep mode consuming less than 1 µA.
Due to its high input impedance, the PWM/EN pin can be used as an enable input.
Connect the pin directly to the supply line, if its function is not needed.
The minimum supply voltage calculates as the sum of the LED forward voltages, the
TLE4309 dropout voltage and the maximum voltage drop across the reference resistor
R
Datasheet
I
Q typ
REF
,
.
=
V
+12V
V
------------
R
REF
REF
REF
100nF
is the reference voltage. (see “Electrical Characteristics” table). The
Block Diagram and Typical Application Circuit
Logic
PWM
/ EN
I
1
2
Bias Supply
Reference
Bandgap
R
REF
GND
4
2
TLE 4309
1.8
Shutdown
Temp.
T L E 4 3 0 9 _ B L OCK DI A GRA M+ A P P CI RCUIT .V S D
. On Page 7, the output current is
5
7
Q
REF
Rev. 1.0, 2007-03-20
TLE4309
R
RE F
(1)