The TL4242 is an integrated, adjustable constant-current source that drives loads up to 500mA. The output current level can be adjusted via an external resistor. The device is designed to supply high-power LEDs (for example, OSRAM Dragon LA W57B) under the severe conditions of automotive applications, resulting in constant brightness and extended LED lifetime. It is provided in the DRJ (QFN) package. Protection circuits prevent damage to the device in case of overload, short circuit, reverse polarity, and overheat. The connected LEDs are protected against reverse polarity as well as excess voltages up to 45V.
An external shunt resistor in the ground path of the connected LEDs is used to sense the LED current. A regulation loop holds the voltage drop at the shunt resistor at a constant level, and that level can be adjusted by selecting the shunt resistance. Furthermore, with the PWM input, the LED brightness can be regulated via duty cycle. Due to high impedance of the PWM input, the PWM pin also can be used as an enable pin.