The IS32LT3174 and IS32LT3120 are single and dual channel specialty drivers with programmable current source, push-button input and integrated fade-in/fade-out. The devices are designed for use in LED-based map lights, dome lights, door lights and other automotive lighting applications.
The IS32LT3174 & IS32LT3120's enhanced features reduce part count compared to the prevailing discrete offerings, which enables automotive manufacturers to develop a compact system design and help reduce time to market. Furthermore, the single and dual integrated LED drivers reduce design complexity and improve system reliability.
The IS32LT3174 & IS32LT3120 consists of a single or dual linear programmable constant current source - a single external resistor is all that is required to adjust the LED current from 10 to 200 mA. Another resistor sets the fade-in and fade-out time with integrated Gamma correction. The devices integrate a 63 step fade-in and fade-out algorithm (Gamma correction), which causes the output LED current to gradually ramp up or down from the full source value to zero after the channel's control pin is pulsed. This feature results in a reduced number of steps for the LED intensity setting while enabling the intensity adjustments to appear more linear to the human eye. The LED current output can be controlled by a momentary contact switch or logic level signal. An internal debounce circuit conditions the input signal so a single press of the mechanical switch does not appear like multiple presses.
The device also integrates protection features, such as open and short LED fault detection and thermal rollback and thermal shut down to increase system longevity and reliability. The output current of both channels are equal to the set value as long as the die temperature of the IC remains below 125°C (Typical). If the die temperature exceeds this threshold, the output current of the device will begin to reduce at a rate of 3%/°C. The device will enter thermal shutdown if the
temperature exceeds 155°C.