原标题：Analogic AAT1451平板电脑高效白光LED驱动方案

　　Analogic公司的AAT1451是四路高集成高效白光LED驱动器,主要用于笔记本电脑,上网本,监视器和手提TV的LCD背光的LED驱动.器件的输入电压从5V到26V,可从DC,点烟适配器或多个锂电池输入,集成的升压转换器提供高达50V的输出,每串LED电流高达30mA可编程,120mA总输出电流可驱动多达481个LED.效率高达93%,主要用在监视器, 笔记本和上网本电脑,手提DVD播放器,手提TV和白光LED背光.本文介绍了AAT1451主要特性, 方框图, 典型应用电路图以及评估板电路图和材料清单, PCB布局图.

　　AAT1451 | Four LED Strings–High Efficiency White LED Driver for LCD Backlighting

　　The AAT1451 is a highly integrated, high efficiency LED backlight solution for notebook, netbook computers, monitors and portable TVs. The device operates from DC inputs, cigarette adapters or multi-cell Li-ion batteries in the voltage range from 5V to 26V.

　　An integrated boost (step-up) converter provides a high voltage output up to 50V for driving series LEDs. Four precision current sinks are programmable up to 30mA per string through one external RSET resistor, supporting up to 481 white LEDs at 120mA total output current.

　　The boost output voltage is determined by the highest total forward voltage of the LED strings, allowing for a wide range of LED characteristics. Each string is PWM dimmed with 90 degree phase shift to minimize ripple currents, and filter capacitor sizes. The PWM input frequency range is 100Hz to 10kHz with a dimming range of 256:1.

　　The integrated boost regulator switching frequency is programmable from 600kHz to 1MHz by external resistor for optimum efficiency and the smallest external L/C filtering components.

　　Boost current mode control provides fast response to line and load transients. Integrated light-load mode ensures highest efficiency across the entire load range.

　　Fault tolerant circuitry extends system life by disabling open and shorted LED(s) strings. The unique high voltage current sinks prevent damage resulting from shorted LEDs. The FAULT pin indicates the presence of shorted LEDs or over-temperature conditions.

　　The AAT1451 is available in a Pb-free, thermally enhanced 16-pin 3x4 TDFN package.

　　AAT1451主要特性:

　　• VIN Range: 5V to 26V

　　• Integrated 50V Boost Converter

　　▪ Maximum IOUT: 120mA

　　▪ Programmable Switching Frequency

　　• 600kHz to 1MHz

　　▪ Up to 93% Efficiency

　　▪ High Efficiency Light-Load Mode

　　• Four White LED Strings

　　▪ Programmable Max Current Sink up to 30mA Each

　　▪ ±2% Accuracy (22mA)

　　▪ ±1.5% Matching (22mA)

　　• Direct PWM Dimming

　　▪ Automatic Phase Shifting

　　▪ Fast Turn-On/Off

　　• Integrated Fault Protection for

　　▪ Independent Disable of Open/Shorted LED(s) String(s)

　　▪ Over-Voltage

　　▪ Over-Temperature

　　• FAULT Indication for Shorted LED(s) and Over-Temperature

　　• Soft-Start Minimizes Inrush Current

　　• TDFN34-16 Low Profile Package

　　• -40℃ to +85℃ Temperature Range

　　AAT1451应用:

　　• Monitors

　　• Notebook and Netbook Computers

　　• Portable DVD Players

　　• Portable TV

　　• White LED Backlight

　　图1.AAT1451方框图

　　图2.AAT1451典型应用电路图

　　图3.AAT1451评估板电路图

　　AAT1451评估板材料清单:

　　AAT1451评估板表面安装电感:

　　AAT1451评估板表面安装电容: