LM36923H: why need PWM input

Hi Fred,

Usually a PWM input is used for brightness control. Those which don't have pins named "PWM input" may have other pin to input PWM.

As for LM36923, you can use an external PWM to control brightness or you can use I2C to control brightness.

BR

Patrick

Hi Patrick,

sorry, let me rephrase,

I notice Flash and RGB LED driver both don't have this PWM input pin,

they use I2C to change brightness mostly,

only backlight has PWM input,

 is there any reason behind this?

Hi Fred,

RGB drivers usually have MCU on PCB, so it's no need to add an additional PWM input, and so dose Flash (however, some flash drivers also have external PWM input pin).

And why do you care about the external PWM pin? Is any customer asking you about it?

BR

Patrick

Hi Yao,

sorry,

I'm confused why this has anything to do with MCU,

I mean my question is why RGB generate their own PWM internally?

Hi Fred,

This internal PWM is used for PWM dimming mode to control brightness. It means whatever your input is (external PWM or I2C), finally it needs to be generated as a PWM with pre-set frequency to control the brightness.

BR

Patrick

Hi Yao,

thanks ,

I got it now, since backlight  is normally in monitor which doesn't have MCU or far away from scalar.

so for those don't have external PWM input,  they will transform the I2C signal to PWM signal they need internally , is that what you mean?

or they use internal oscillator?

Hi Fred,

Yes, that's what I mean.

BR

Patrick

Hi Yao,

to be clear, I think you mean they use internal oscillator to generate PWM instead of I2C, right?