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UCC28730-Q1: HV Pin Abs Max Voltage

Jacob Wyrick
Expert 6085 points
Part Number: UCC28730-Q1
Other Parts Discussed in Thread: UCC28730

Hi team,

I'm looking to use the UCC28730-Q1 on a 400VDC HV battery back-up supply to a low voltage, 12V rail. The 400V battery can face transients up to 800V, but the Abs Max of the UCC28730-Q1 is 700V.

Can the UCC28730-Q1 survive the 800V transient? Do we have any guidance on transient max duration above 700V or how to protect the HV pin?

Thanks,

Jacob

  • 0
    TI__Guru 71105 points

    Hello,

    The absolute maximum on a device is not to be exceeded.  So the HV pin cannot handle more than 700V.

    You could drop the HV voltage down with a series pass regulator to ensure the HV voltage does not exceed 700V.  You can do this with a high voltage Zener diode a biasing resistor and a NPN transistor.

    Regards,

  • 0 in reply to Mike O'
    TI__Expert 6085 points

    Hi Mike,

    Thanks for the feedback! Do you happen to have a reference circuit diagram or application note for this type of series pass regulator?

    Thanks,

    Jacob

  • +1 in reply to Jacob Wyrick
    TI__Guru 71105 points

    Hello,

    The step by step design procedure for this device is part of the data sheet.  There are many other application notes for this device that can be found at the following link. https://www.ti.com/product/UCC28730?keyMatch=UCC28730&tisearch=search-everything&usecase=GPN#tech-docs

    There is not an application note for the Series pass regulator but it should not be that hard to setup.  You use an NPN transistor and connect the collector to the bulk input and the emitter to the HV pin of the UCC28730.  You connect a resistor from the collector to base and a Zener diode from the base to ground.  The resistor needs to be size to supply the Zener diode with it's recommended current.

    The other option is replacing the Zener with a resistor.  Setup the voltage divider to put the high voltage pin below 700 V.  600 V would be a good choice.  This still needs the NPN transistor and you need to size that for the voltage it could see across as well as the current suppling  the HV pin.

    Regards,