Linear 公司的LT3518 LED是电流模式DC/DC转换器，内置了用来驱动LED的2.3A， 45V开关。LT3518具有3000:1真色彩PWM调光比，从250kHz 到 2.5MHz的可调工作频率，主要应用在显示器背景光，汽车电子，照明以及扫描仪。本文介绍LT3518的主要性能，方框图以及多种典型的应用电路图。

      LT3518 - Full-Featured LED Driver with 2.3A Switch Current
      The LT®3518 is a current mode DC/DC converter with an internal 2.3A， 45V switch specifically designed to drive LEDs. The LT3518 operates as a LED driver in boost， buck and buck-boost modes. It combines a traditional voltage loop and a unique current loop to operate as a constant-current source or constant-voltage source. Programmable switching frequency allows optimization of the external components for efficiency or component size. The switching frequency of the LT3518 can be synchronized to an external clock signal. The LED current is externally programmable with a 100mV sense resistor. The external PWM input provides 3000:1 LED dimming. The CTRL pin provides further 10:1 dimming ratio.

      The LT3518 is available in the tiny footprint QFN UF16 (4mm 4mm) package. The LT3518 provides a complete solution for both constant-voltage and constant-current applications.

主要特性：
■ 3000:1 True Color PWMTM Dimming Ratio
■ 2.3A， 45V Internal Switch
■ 100mV High Side Current Sense
■ Open LED Protection
■ Adjustable Frequency: 250kHz to 2.5MHz
■ Wide Input Voltage Range:
Operation from 3V to 30V
Transient Protection to 40V
■ Operates in Boost， Buck Mode and Buck-Boost Mode
■ Gate Driver for PMOS LED Disconnect*
■ Constant-Current and Constant-Voltage Regulation
■ CTRL Pin Provides 10:1 Analog Dimming
■ Low Shutdown Current: <1μA
■ Tiny (4mm 4mm) 16-Pin QFN Package

应用：
■ Display Backlighting
■ Automotive and Avionic Lighting
■ Illumination
■ Scanners

图1、LT3518方框图

图2、典型应用

图3、降压模式1.5A LED驱动器电路

图4、500mA 5V-12V升压转换器

图5、降压/升压模式 LED驱动器电路