NS LM3431 3路LED电流控制方案

NS 公司的LM3431集成了3路线性电流控制器和升压开关控制器,非常适合用来驱动LED背景光. LM3431能驱动3个外接NPN晶体管或MOSFET,向3路LED串提供高精度的恒定电流.输出电流超过200mA,并可扩展成驱动6个LED串.输入电压3V-36V,调光频率高达25kHz,采用模拟和数字两种方式调光,对比度大于100:1.本文介绍了LM3431的主要特性,方框图,典型应用电路以及评估板完整电路图与材料清单(BOM).

The LM3431 is a 3-channel linear current controller combined with a boost switching controller ideal for driving LED backlight panels in space critical 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 200 mA. The LM3431 can be expanded to drive as many as 6 LED strings.
The boost controller drives an external NFET switch for stepup regulation from input voltages between 5V and 36V. The LM3431 features LED cathode feedback to minimize regulator headroom and optimize efficiency.
A DIM input pin controls LED brightness from analog or digital control signals. Dimming frequencies up to 25 kHz 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.
Additional features include LED short and open protection, fault delay/error flag, cycle by cycle current limit, and thermal shutdown for both the IC and LED array. The enhanced
LM3431A features reduced offset voltge for higher accuracy LED current.
LM3431主要特性:
■ 3-channel programmable LED current
■ High accuracy linear current regulation
■ Analog and digital PWM dimming control
■ Up to 25kHz dimming frequency
■ >100:1 contrast ratio
■ Integrated Boost controller
■ 5V-36V input voltage range
■ Adjustable switching frequency up to 1MHz
■ LED short and open protection
■ Selectable fault shutdown or automatic restart
■ Programmable fault delay
■ Programmable cycle by cycle current limit
■ Output Over Voltage Protection
■ No Audible Noise
■ Enable pin
■ LED Over-Temperature shutdown input
■ Thermal Shutdown
■ TSSOP-28 exposed pad package
LM3431应用:
■ Automotive Infotainment Displays
■ Small to Medium Format Displays



图1. LM3431方框图



图2.LM3431应用电路图



图3.LM3431评估板完整电路图
评估板材料清单(BOM):