Three-Channel LED Driver Enables Compact and Reliable Displays

The LM3431 is a 3-channel linear-current controller, integrated with a boost switching controller, offering a compact solution for LED backlight panels.

Additional protection feature - such as LED short and open protection, fault delay/error flag, cycle-by-cycle current limit, and thermal shutdown for both the IC and LED array - make these drivers suitable for demanding automotive applications.

The LM3431 drives 3 external NPN transistors or MOSFETs to deliver high-accuracy constant current to 3 LED strings. Output current is adjustable to drive strings in excess of 200mA. The LM3431 can also be expanded to drive as many as 6 LED strings.

The boost controller drives an external NFET switch for step-up regulation from input voltages between 5V and 36V. The LM3431 features LED cathode feedback to minimise regulator headroom and optimise efficiency. The DIM input pin controls LED brightness from analogue- or digital-control signals. Dimming frequencies up to 25kHz are possible with a contrast ratio of 100:1. Contrast ratios greater than 1000:1 are possible at lower dimming frequencies.

The LM3431 eliminates audible noise problems by maintaining constant output-voltage regulation during LED dimming. The enhanced LM3431A features reduced offset voltage for higher-accuracy LED current.

 

FEATURES 3-channel programmable LED current High-accuracy linear-current regulation Analogue and digital PWM dimming control Up to 25kHz dimming frequency Integrated boost controller 5V to 36V input voltage range Adjustable switching frequency up to 1MHz Selectable fault shutdown or automatic restart Programmable fault delay and cycle-bycycle current limit Output over-voltage protection LED over-temperature shutdown input Thermal shutdown TSSOP-28 exposed-pad package

APPLICATIONS Automotive infotainment displays Small-to-medium format displays

 

National Semiconductor / LM3431