National Semiconductor - LED Driver with Dynamic Headroom Control for Automotive LCD Backlight Applications

The LM3492’s dynamic headroom control feature dynamically adjusts the LED supply voltage through the boost converter feedback to the lowest level required to provide optimal system efficiency. Three embedded MOSFETs reduce system complexity and cost.

Technical Features of National’s LM3492 LED Driver
National’s LM3492 integrates a boost converter and a two-channel current regulator to efficiently and cost-effectively drive two independently dimmable LED strings with a maximum power of 15W and an output voltage of up to 65V. Integrated fast slew rate current regulators allow high frequency and narrow pulse width dimming signals to achieve a very high contrast ratio of 1000:1. The LED current is programmable from 50 mA to 200 mA by a single resistor.

To maximize the efficiency, dynamic headroom control (DHC) automatically adjusts the LED driving voltage to a minimum level. DHC also facilitates a single bill of materials for different number of LEDs in a string, which is required for backlight panels of different size, thereby reducing overall development time and cost.

The LM3492 includes a versatile COMM pin which serves as a bi-directional input/output pin interfacing with an external MCU for command and diagnostic functions.