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UCC21750: DESAT Internal P-MOSFET

Francis Jiang
Expert 3470 points
Part Number: UCC21750


Tool/software:

Hi Team,

Customer ask that how the DESAT internal MOSFET work when short-circuit happened and doesn't happen? I see here is a P-MOSFET, quite difficult to understand through the explanation in the datasheet.

BRs,

Francis

  • 0
    TI__Mastermind 23226 points

    Hi Francis,

    The internal FET should be an NMOS shown in the image above. It is there to initialize the C_BLK capacitor to 0V when OUT is LOW. When output goes HIGH, this NMOS opens, and the C_BLK begins to charge. If the IGBT is conducting minimal current, the current will drain through D_HV and the DESAT voltage will remain below the threshold. If the IGBT Vce is desaturated due to high current, the DESAT voltage charges to the threshold, and then the output will enter soft turn-off an the gate driver will report a fault.

    Best regards,

    Sean