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LT3966 and max channel current

Hello, i'm concerned about LT3966 SW pin max current specs. Basically i've used all 4 channels, 31V 1.8A each, should be good with a 4 layer pcb design and active cooling underneath or is it over-specs?

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  • Hello Zefram,

    this won't work. The switch in a boost regulator does 'see' the input current. To obtain 31V and 1,8A as output load you demand for 56W/channel(!!)

    To deliver 56W with 12V input you end up at 4.65A input current. And this simplified calculation does not take <100% efficiency or ripple current into account. But your app is far beyond the capabilities of the LT3966.

    If I take the 12V Vin and 31VLED as fixed I think a LED current of 400mA is achievable with careful design and good thermals

    The examples in the ds show 25W/channel. Take this values as guidance what is possible with our parts.

    kind regards


  • Thanks for the answer,
    do you have any advice on which driver i can use for such application? May be LT8391 a good alternative (I'd be using 4 of them to control the strips, each one with 43.5v, 800mA (totalling at 34W per Channel))?

    Thank you again

  • Yes, the LT8391 is a part which can deliver the desired power. Maybe the LT8391A is ok as well and saves some space as higher switching frequency allows smaller inductor.

    For sure a much bigger design than one LT3966, but your power level does not allow for a simpler solution.

    kind regards