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High side dimming in LM3423

David Park
Expert 6680 points
Other Parts Discussed in Thread: LM3423

Hi,

In LM3423 boost application,

for high side dimming, PFET and BJT is needed.

But if use low side dimming, only NFET is needed.

Could you let me know why high side dimming is applied usually?

In case of LM3423, when over current protection, dimming FET is not disabled.

So high side dimming can't protect LED short or over current.

I want to know what is advantage of high side dimming?

Thanks.

  • 0
    TI__Mastermind 25500 points
    Some applications require (or desire) to have one end of the LED string connected to system ground. That requires high side dimming and is about the only reason you would use it. For designs that do not require a direct ground connection the low side dimming is cheaper and easier.