Texas Instruments' TL4242 is a linear, constant-current, single channel LED driver capable of sourcing up to 500mA. The device is also capable of operating from a supply of up to 42V, allowing a large LED string to be driven through a single device. The TL4242 has several features that make it ideal for simple applications. The high side source and low side sense resistor make control of the constant current quite easy. The PWM pin can be used as a simple enable function (high is ON, low is OFF), or it can be manipulated by an external controller to dim the LED string or flash the LED string as needed.
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.
Functional Block Diagram
- Adjustable constant current up to 500mA (±5%)
- Wide input voltage range up to 42V
- Low drop voltage
- Open-load detection
- Overtemperature protection
- Short-circuit proof
- Reverse-polarity proof
- Wide temperature range: –40°C to 150°C