ADI LT3935 36V4A同步降压LED驱动器解决方案
ADI工司的LT3935是单片式同步降压DC/DC转换器, 采用固定频率,峰值电流控制并为LED串提供PWM调光. LED电流通过CTRL引脚上的模拟电压或脉冲占空比进行编程设定.输出电压限制可通过连接至FB引脚的电阻分压器进行设置. 通过RT引脚上连接的外部电阻或SYNC/SPRD引脚上的外部时钟,可在200kHz至2MHz范围内对开关频率进行编程. 当可选的展频功能使能时,频率在100%至125%范围内变化以减少EMI.其他特性包括LED电流监控,精确的EN/UVLO引脚阈值,针对开路和短路负载条件的开漏故障报告和热关断.LT3935采用专有的Silent Switcher技术以实现低EMI. 3.6V 至 36V 输入电压范围,0V 至 36V LED 灯串电压. 20:1 模拟或占空比 LED 电流控制,开路/短路 LED 故障指示,具有监视器输出的精确 LED 电流检测,可编程 UVLO和耐热性能增强型. ±1.5% LED 电流调节, ±1.2% 输出电压调节.采用 28 引脚 (5mm × 4mm) LQFN 封装.主要用在汽车照明,工业和通用照明.本文介绍了LT3935主要特性,框图和多种应用电路, 评估板DC2987A主要特性, 测试建立图和电路图,材料清单.
The LT®3935 is a monolithic, synchronous, step-down DC/DC converter that utilizes fixed-frequency, peak current control and provides PWM dimming for a string of LEDs.
The LED current is programmed by an analog voltage or the duty cycle of pulses at the CTRL pin. An output voltage limit can be set with a resistor divider to the FB pin.
The switching frequency is programmable from 200kHz to 2MHz by an external resistor at the RT pin or by an external clock at the SYNC/SPRD pin. With the optional spread spectrum frequency modulation enabled, the frequency varies from 100% to 125% to reduce EMI.
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