原标题：Linear LT3965八开关矩阵LED调光器系统方案

　　Linear公司的LT3965是八开关矩阵LED调光器,具有八个单独控制的17V/330mΩ NMOS开关,八个开关可并联/或串联,采用I2C串口和MCU通信,每个开关可单独开/关/调光1-4个LED,数字可编程256:1 PWM调光,主要用在汽车LED头灯,大型LED显示屏,自动照相机闪光设备,RGBW彩色混合照明.本文介绍了LT3965主要特性,框图和几种应用电路,以及演示板DC2218A特性,测试建立图,电路图,材料清单和PCB元件布局图.

　　The LT®3965 is an LED bypass switching device fordimming individual LEDs in a string using a commoncurrent source. It features eight individually controlledfloating source 17V/330mΩ NMOS switches. The eightswitches can be connected in parallel and/or in series tobypass current around one or more LEDs in a string. TheLT3965 uses the I2C serial interface to communicate withthe microcontroller. Each of the eight channels can beindependently programmed to bypass the LED string inconstant on or off,or PWM dimming with or without fadetransition. Using the fade option provides 11-bit resolution

　　logarithmic transition between PWM dimming states.

　　The LT3965 provides an internal clock generator and alsosupports external clock source for PWM dimming. TheLT3965 reports fault conditions for each channel such asopen LED and shorted LED. The four address select pinsallow 16 LT3965 devices to share the I2C bus. The deviceis available in a 28-lead TSSOP package.

　　LT3965主要特性:

　　Eight Independent 17V 330mΩ NMOS Switches

　　Independent On/Off/Dimming Control of 1 to 4 LEDsfor Each Switch

　　I2C Multidrop Serial Interface with ProgrammableOpen LED and Shorted LED Fault Reporting

　　16 Unique I2C Addresses

　　VDD Range: 2.7V to 5.5V and VIN Range: 8V to 60V

　　Digital Programmable 256:1 PWM Dimming

　　Fade Transition Between PWM Dimming States

　　Optional Internal Clock Generator or External ClockSource for PWM Dimming

　　Open LED Overvoltage Protection

　　Flicker Free PWM Dimming

　　LT3965应用:

　　Automotive LED Headlight Clusters

　　Large LED Displays

　　Automated Camera Flash Equipment

　　RGBW Color Mixing Lighting

　　图1.LT3965框图

　　图2.LT3965降压模式LED驱动器电路

　　图3.LT3965双降压模式LED驱动器和升压预调整器电路

　　演示板DC2218A

　　Demonstration circuit DC2218A is a matrix LED dimmersystem featuring the LT3965 8-switch matrix LED dimmerIC. There are 16 500mA LEDs that can be individuallyturned on, off, or PWM dimmed with two 8-switch LEDdimmer LT3965 ICs. The two strings of LEDs are drivenwith two buck LED driver outputs of the LT3797 triple LEDcontroller IC. The third channel of the LT3797 serves as a30V pre-boost voltage regulator to provide a proper inputvoltage to the two buck LED driver channels. DC2218Acan be driven from a 9V to 30V input and can survivetransients up to 36V.

　　A pre-programmed DC2026C Linduino™ One demo circuitis attached to the DC2218A matrix LED dimmer shield tocreate a full matrix LED dimmer system. With the Linduino One attached as an under-shield microcontroller board, theentire system can be powered from either a 9V to 36V labpower supply or battery connected to the EMIVIN bananajacks or from a 12V 4A+ AC/DC converter connected tothe J7 barrel jack connector.

　　DC2218A can be operated by connecting 12V power to theinput and selecting 7 pre-programmed patterns with rotaryswitch S1. When connected to a PC through a USB cable,an eighth setting of S1 (position 7) allows DC2218A to beoperated with a graphical user interface (GUI).

　　The LT3965 data sheet gives a complete description ofthe part, operation and applications information. The datasheet must be read in conjunction with this demo manualfor demonstration circuit DC2218A. The LT3965EFE isassembled in a 28-lead plastic TSSOP (FE) package witha thermally enhanced ground pad. Proper board layout is essential for maximum thermal performance.

　　图4.演示板DC2218A测试建立图

　　演示板DC2218A材料清单: