An implementation scheme of PWM dimming function for 16-channel LED driving chip is presented in this paper. The dimming control of LED is realized changing the duty ratio of the LED average current through all the channels′ LEDs by PWM method. The module is composed of 128-bit serial shifting register,8-bit data latch,8-bit counter and 8-bit PWM grey-level comparator to output a PWM control signal with 256-order grey dimming function. The external data clock frequency is 25 MHz. The internal oscillator frequency is 1.2 MHz. The overall function is implemented by programming with Verilog HDL language.%介绍了一种应用于多通道恒流LED驱动芯片的PWM调光功能的实现方案，通过脉宽调制来改变流过各个通道LED的平均电流，进而实现了LED的调光控制。该模块由128 b串行移位寄存器，8 b数据锁存器，8 b计数器，以及8 b PWM灰度比较器构成，输出具有256阶灰度调节功能的PWM控制信号。外部数据时钟采用25 MHz，内部振荡器采用1.2 MHz。整体功能由Verilog HDL语言编程实现。
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