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dual useage of gate output on ADM6820

I had a question about a way to use the ADM6820 gate output for a active high enable power device (like a DC/DC converter) as well as for the intended N mosfet gate. This is so I can use the same device for all my needs. So it wasn't clear to me if when the gate output is still tied to ground after the UVLOW is cleared.  Also the data sheet does not state how much current the gate output can sink when it is driving to ground. Would it be enouph to drive a pullup resistor in the low state in the mA range?  I attached a rouph circuit for what I was thinking about.

Thanks

ADM6820_ENABLE_DRIVER.TIF
  • Hi,

    based on the GATE Turn-Off Time spec and GATE Voltage spec on the datasheet, you can roughly calcualted the gate pull down strengh, which is about 400uA. so the 4.7k pullup might be too strong.

    the gate would be grounded after UVLO, if not enabled. you can see this in FIg 12 and 13 of the TPC section.

    If you only want to drive the enable of a DCDC, i would recommand ADM1085-87 series sequencers, they are lower cost parts designed for this type of applicaitons.

    Ren

  • Ren,

    That was aood observation on estimating out the gate drive. I was aware of the ADM1085 but I was wanting to keep the unique part count down to a minimum. I could concider working out something that will work with a low amount of pull down drive. I was thinking I could use a buffer as well but I am afraid it might glitch on power up and starts to get more complicated.

    Thanks.

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