Linear LT3598升压LED串驱动方案

Linear 公司的LT3598是固定频率升压LED串驱动转换器,输出电压高达44V,可驱动多达6个LED串. LT3598的开关频率由外接电阻在200kHz到2.5MHz间调整,而PWM调光提供高达3000:1的调光比.LED的电流可匹配到本世纪末1.5%. LT3598的输入电压范围从3.2V到30V,主要用在笔记本电脑显示屏,中等尺寸显示评和汽车LCD显示屏.本文介绍了
LT3598主要特性,方框图,驱动60个白光LED的典型应用电路和驱动40个白光LED电路图, 采用汽车电池驱动20个白光LED电路图.

The LT 3598 is a fixed frequency step-up DC/DC converter designed to drive up to six strings of LEDs at an output voltage up to 44V. LED dimming can be achieved with analog dimming on the CTRL pin, and with pulse width modulation dimming on the PWM pin. The LT3598 accurately regulates LED current even when the input voltage is higher than the LED output voltage. The switching frequency is programmable from 200kHz to 2.5MHz through an external resistor.

Additional features include programmable overvoltage protection, switching frequency synchronization to anexternal clock, LED current derating based on junction temperature and/or LED temperature, LED string disable control, OPENLED alert pin and output voltage limiting when all LED strings are disconnected. The LT3598 is available in a thermally enhanced 24-pin (4mmx4mm)QFN package.

主要特性:
True Color PWM Dimming Delivers Up to 3000:1 Dimming Ratio
Drives Six Strings of LEDs at Up to 30mA
1.5% Accurate LED Current Matching
Wide Input Voltage Range: 3.2V to 30V
Output Voltage Up to 44V
Regulates Current Even When VIN > VOUT
Disconnects LEDs in Shutdown
Programmable Open LED Protection (Regulated)
OPENLED Alert Pin
Programmable LED Current Derating
Adjustable Frequency: 200kHz to 2.5MHz
Synchronizable to an External Clock
Parallel Channels for Higher Current per LED String
Thermally Enhanced 4mmx4mm QFN Package

应用:
Notebook Computer Display
Medium Size Displays
Automotive LCD Display



图1.LT3598方框图



图2.LT3598典型应用电路



图3.LT3598驱动40个白光LED电路图



图4.LT3598驱动30个白光LED电路图



图5.采用汽车电池驱动20个白光LED电路图