Adjustable Linear Low Dropout LED Driver TLE4309 Features Adjustable constant current up to 500 mA Operating supply voltage range 4.5 V to 24 V Maximum supply voltage up to 45 V Low dropout voltage PWM / ENABLE input << 1 A quiescent current when disabled Overtemperature protection PG-TO263-7 Short circuit proof Reverse polarity protection Operating junction temperature range: -40 C to 150 C Suitable for applications up to 85 C ambient temperature. Green Product (RoHS compliant) Functional Description The TLE4309 is an integrated adjustable constant current source for driving loads up to 500 mA. The output current level can be adjusted with an external shunt resistor. Supplying high power LEDs with the TLE4309 ensures constant brightness independent from supply voltage or LED forward voltage spread. Therefore, LED lifetime is extended by protecting from overcurrent and overtemperature The PWM/EN input permits LED brightness regulation by pulse width modulation. Setting the pin to low switches off the IC entirely. Due to the high impedance of the PWM/EN input, the TLE4309 can be used as a protected high side switch. Protection circuits prevent from damage to the IC in case of overload, short circuit, and reverse polarity. A chip temperature monitoring circuit shuts off the power stage and prevents the IC from destruction under fault conditions. In case of negative input voltage, a leakage current is flowing only from the output to the input, hence the LED are protected against reverse supply. Input voltage peaks up to 45 V are absorbed by the IC, preventing the LEDs from overcurrent. The TLE4309G is provided in the surface mounted PG-TO-263 package with excellent thermal resistance. Type Package Marking TLE4309G PG-TO263-7-1 TLE4309 Datasheet 1 Rev. 1.0, 2007-03-20 TLE4309 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 V REF I = ------------ Qt, yp (1) R REF where V is the reference voltage. (see Electrical Characteristics table). The REF equation applies in a range of 0.39 R 1.8 . On Page 7, the output current is REF shown as a function of the reference resistance. TLE 4309 I Q 1 7 PWM Bias Supply 100nF / EN 2 Temp. Shutdown Bandgap +12V Reference Logic 5REF 4 TLE430 9 BLOCKDIAGRAM+APPCIRCUIT.VSD GND R REF Figure 1 Block Diagram and Typical Application Circuit 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 A. 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 . REF Datasheet 2 Rev. 1.0, 2007-03-20 optional