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nxp公司的pca9685是16路12位pwm不是fm+i2c总线led控制器，每个led输出有它独立的12位分辨率(4096步)固定频率pwm控制器，工作频率从40hz到1000hz，占空比从0%到100%.工作电压2.3 v 到5.5 v，主要用在rgb或rgbaled驱动器，led状态显示器，led显示器，lcd背光和手机或手持设备的键盘背光.本文介绍了pca9685主要特性和优势，方框图以及典型应用电路图和lcd背光应用电路图.pca9685: 16-channel， 12-bit pwm fm+ i2c-bus led controllerthe pca9685 is an i2c-bus controlled 16-channel led controlleroptimized for lcd red/green/blue/amber (rgba) color backlightingapplications. each led output has its own 12-bit resolution (4096steps) fixed frequency individual pwm controller that operates at aprogrammable frequency from a typical of 40 hz to 1000 hz with aduty cycle that is adjustable from 0 % to 100 % to allow the led tobe set to a specific brightness value. all outputs are set to thesame pwm frequency.each led output can be off or on (no pwm control)， or set at itsindividual pwm controller value. the led output driver isprogrammed to be either open-drain with a 25 ma current sinkcapability at 5 v or totem pole with a 25 ma sink， 10 ma sourcecapability at 5 v. the pca9685 operates with a supply voltage rangeof 2.3 v to 5.5 v and the inputs and outputs are 5.5 v tolerant.leds can be directly connected to the led output (up to 25 ma， 5.5v) or controlled with external drivers and a minimum amount ofdiscrete components for larger current or higher voltage leds.the pca9685 is in the new fast-mode plus (fm+) family. fm+ devicesoffer higher frequency (up to 1 mhz) and more densely populated busoperation (up to 4000 pf).although the pca9635 and pca9685 hav